Peculiar high engine temp scenario...98 LX470 (1 Viewer)

[geanes]

98 LX470, 250k on the clock. I monitor real-time with a Scangauge. Background, dealer installed new OEM rack back in Feb and failed to refill radiator. Engine overheated, but I caught it in time (pretty sure). Compression test indicated 152-154 on all 8 cylinders with a very low variance (seemed healthy to me). Dealer installed new thermostat and gasket. At least, they said they did, but couldn't provide me the thermostat they removed (kind of thinking they didn't replace it at this point). Replaced radiator, upper/lower hoses with a CSF back in April and filled with 50/50 Toyota red. Engine routinely ran at 188 since I got it in 2016. I have "rinsed" the radiator and trans cooler with "spot-free" rinse several times the past few months.

Ok, so over the first few months of summer I was noticing that my "normal" operating temp was 190. No real alarms there. It would hold steady at that temp. But, as July arrived and brought the 100 degree days we know so well here in TX, I started seeing the operating temp rise during "load". It would climb to 195 and then drop back to 190 when not on the gas.

Now, it climbs pretty quick to 198-200 when under any kind of load, but drops to 188-190 when coasting. This happens whether it's 107 degrees in the middle of the day or 85 degrees in the middle of the night. The moment I get on the gas at all, the temp steadily rises. I've seen as high as 205 before (long, shallow hill at night in West Texas). I have burped the system a few additional times as a precaution. Required very little coolant (if any).

I drove in CO back in July. The engine would stay 188-190 on steep off-road trails with the engine under load as long I was in 4Lo. If I was 4Hi, the higher temps would manifest.

So, last night, I removed the rad cap (engine off) and coolant was at the base of the neck (as it normally is). The overflow was a tad above "low". I started the motor with the rad cap off and the coolant rose in the neck pretty quick until it wanted to overflow. I turned the motor off and waited 30 minutes for the coolant to drop in the neck. Pretty sure that's normal (though I've read people suggesting taking the cap off, turning on the motor and observing if the coolant is flowing). I check the fan as well. I manually attempted to "spin" it. It would rotate about 1/8-1/4 of a turn before stopping. There was a little resistance when attempting to spin it. Again, pretty sure that's normal and my fan clutch is fine.

At this point, I'm at a loss. I could chalk up the temps to higher ambient for a short while. Heck, I could even chalk it up to the rig being loaded. But, I'm in daily drive configuration the last month and the temp rises anytime I'm on the gas (even just a little). It seems to really spike quick once I hit 55mph. Any speed above that accelerates the temp rise quicker. Part of me is thinking back to the dealer and wondering if A) they put the t-stat in incorrectly (jiggle valve oriented down) or B) they didn't replace the t-stat at all, but said they did (they have a TERRIBLE track record with me r.e. honesty after replacing my steering rack and then saying my coolant was "trapped" in the heater core to explain why there was no coolant in my radiator). Seems odd though that at idle, my engine runs steady 188-190 and fan changes speed from time to time and the aux fan kicks on as normal.

Thinking it's time to completely flush the coolant (5 months old), replace the t-stat and o-ring and then refill again with Toyota Red (mixed 50/50 with distilled water) and then burp the system all over again.

 

[ramangain]

Just replace the t-stat if you are getting ancy. Mine hovers around 194F and has for three years and an older t-stat (I don't know the history of it). No ill effects so far.

While towing up the mountains I saw 217F. Again, no ill effects so far, no drop in coolant level, no boiling/steam events, etc.

 

[MongooseGA]

The temps alone wouldn't concern me based on what I see in my truck, but the change in the temps would have me thinking. Like mentioned above, do the thermostat and get some new fluid in it. Is the radiator any more plugged with debris than it would have been before this started happening?

 

[geanes]

The temps alone wouldn't concern me based on what I see in my truck, but the change in the temps would have me thinking. Like mentioned above, do the thermostat and get some new fluid in it. Is the radiator any more plugged with debris than it would have been before this started happening?

Radiator fins seem clean. There were some bugs in the trans cooler, but the fins are fine on it as well. The temps drop quick when off the gas. I'll pick up a new T-stat and o-ring this week along with fresh coolant. Thinking of maybe getting a pressure test done on the cooling system while I'm at it. Just so weird that it ran consistent 188 for years. The change really started to occur post dealer foul up. Really hoping it's just a t-stat issue.

 

[JunkCrzr89]

Sounds like the thermostat is sticking and not opening completely.

 

[CorporalClegg]

Given the history of your situation it may be worth it for you to find a indy shop and pay 1hr diag. ~120 bucks to have them use a gas analyzer and check for combustion gases in the cooling system. Make sure they're using a gas analyzer and not just "block tester" fluid as they're much more sensitive. Ask for a print out or photo of the results. Any hydrocarbons is bad but very little amounts may not be worth the cost of head gaskets.

Those temperatures aren't anything to be concerned with but, the fact you're seeing higher temps after that trip to dealer is worry some.

 

[FxFormat]

How do you guys feel about running 70% distilled 30% coolant if you live in climates that doesn't freeze over? At this point change the thermostat and see if that'll help.

 

[jahawk]

In my "fast" cars I run distilled water and Water Wetter only. I see around 10-15 degree drop by doing this. I've never bothered in the LX since it does see freezing temps occasionally.

Jim

 

[abuck99]

How do you guys feel about running 70% distilled 30% coolant if you live in climates that doesn't freeze over? At this point change the thermostat and see if that'll help.

Not a good idea for this reason: the 50/50 mix of LL and SLL2 coolant must have and provide correct chemistry to lubricate, protect from corrosion, and withstand 50k or 100k duty cycle. Reducing that mixture in favor of more water wouldnt be good for a long term service interval.

Gary- do another flush and replace Tstat and radiator cap. From under the radiator, look up into gap between backside of condenser and front side of radiator; check the front lower side of the radiator for build up grass or debris.

When is the last time you flushed transmission? Do you monitor trans temps? More trans slip will spike trans temps, which will make it your ect run higher.

 

[JunkCrzr89]

Not a good idea for this reason: the 50/50 mix of LL and SLL2 coolant must have and provide correct chemistry to lubricate, protect from corrosion, and withstand 50k or 100k duty cycle. Reducing that mixture in favor of more water wouldnt be good for a long term service interval

Distilled water also has a boiling point of 212* (assuming constant pressure), whereas coolant has a much higher boiling point of like +300 or something. I think a 70:30 mix of distilled:coolant has a BP of 250, whereas a 50:50 mix has a BP of 265. Thus, you're always better off with 50:50 mix even in hot climates where freezing doesn't occur.

 

[nissanh]

How old is the radiator? Can you inspect the core through the radiator fill cap?

The amount of ethyleneglycole (coolant) changes the physical properties of the solvent, which is water. Adding a solute to a solvent will lower the freezing point and increase the boiling point of the solution. More solute you add, higher the deviation. The process is called Colligative properties.

 

[flintknapper]

Sounds like the thermostat is sticking and not opening completely.

My thought as well. Had a nearly new (2 week old OEM T-stat) stick completely closed on my Wife's LX a couple of years ago, so it can certainly happen. Also...the increasing incidences of 'fake' OEM parts on the market...makes it harder and harder to know that you are getting quality Toyota parts.

 

[Beau]

If you followed the other "2uz operating temp thread" I had the same problem as you and my cruising temps are around 203 constant. After changing out what appeared to be a good OEM thermostat for another one I bought at a toyota dealer, temps had dropped from 205 to 203. Did everything else and not sure what else it could be. I'll be following this thread to see if you have any more luck than me.

 

[Leandro]

what about the fan clutch? Have you tested it?

 

[BamaCruzer]

98 LX470, 250k on the clock. I monitor real-time with a Scangauge. Background, dealer installed new OEM rack back in Feb and failed to refill radiator. Engine overheated, but I caught it in time (pretty sure). Compression test indicated 152-154 on all 8 cylinders with a very low variance (seemed healthy to me). Dealer installed new thermostat and gasket. At least, they said they did, but couldn't provide me the thermostat they removed (kind of thinking they didn't replace it at this point). Replaced radiator, upper/lower hoses with a CSF back in April and filled with 50/50 Toyota red. Engine routinely ran at 188 since I got it in 2016. I have "rinsed" the radiator and trans cooler with "spot-free" rinse several times the past few months.

Ok, so over the first few months of summer I was noticing that my "normal" operating temp was 190. No real alarms there. It would hold steady at that temp. But, as July arrived and brought the 100 degree days we know so well here in TX, I started seeing the operating temp rise during "load". It would climb to 195 and then drop back to 190 when not on the gas.

Now, it climbs pretty quick to 198-200 when under any kind of load, but drops to 188-190 when coasting. This happens whether it's 107 degrees in the middle of the day or 85 degrees in the middle of the night. The moment I get on the gas at all, the temp steadily rises. I've seen as high as 205 before (long, shallow hill at night in West Texas). I have burped the system a few additional times as a precaution. Required very little coolant (if any).

I drove in CO back in July. The engine would stay 188-190 on steep off-road trails with the engine under load as long I was in 4Lo. If I was 4Hi, the higher temps would manifest.

So, last night, I removed the rad cap (engine off) and coolant was at the base of the neck (as it normally is). The overflow was a tad above "low". I started the motor with the rad cap off and the coolant rose in the neck pretty quick until it wanted to overflow. I turned the motor off and waited 30 minutes for the coolant to drop in the neck. Pretty sure that's normal (though I've read people suggesting taking the cap off, turning on the motor and observing if the coolant is flowing). I check the fan as well. I manually attempted to "spin" it. It would rotate about 1/8-1/4 of a turn before stopping. There was a little resistance when attempting to spin it. Again, pretty sure that's normal and my fan clutch is fine.

At this point, I'm at a loss. I could chalk up the temps to higher ambient for a short while. Heck, I could even chalk it up to the rig being loaded. But, I'm in daily drive configuration the last month and the temp rises anytime I'm on the gas (even just a little). It seems to really spike quick once I hit 55mph. Any speed above that accelerates the temp rise quicker. Part of me is thinking back to the dealer and wondering if A) they put the t-stat in incorrectly (jiggle valve oriented down) or B) they didn't replace the t-stat at all, but said they did (they have a TERRIBLE track record with me r.e. honesty after replacing my steering rack and then saying my coolant was "trapped" in the heater core to explain why there was no coolant in my radiator). Seems odd though that at idle, my engine runs steady 188-190 and fan changes speed from time to time and the aux fan kicks on as normal.

Thinking it's time to completely flush the coolant (5 months old), replace the t-stat and o-ring and then refill again with Toyota Red (mixed 50/50 with distilled water) and then burp the system all over again.

Temps sound within normal range to me.

 

[2001LC]

98 LX470, 250k on the clock. I monitor real-time with a Scangauge. Background, dealer installed new OEM rack back in Feb and failed to refill radiator. Engine overheated, but I caught it in time (pretty sure). Compression test indicated 152-154 on all 8 cylinders with a very low variance (seemed healthy to me). Dealer installed new thermostat and gasket. At least, they said they did, but couldn't provide me the thermostat they removed (kind of thinking they didn't replace it at this point). Replaced radiator, upper/lower hoses with a CSF back in April and filled with 50/50 Toyota red. Engine routinely ran at 188 since I got it in 2016. I have "rinsed" the radiator and trans cooler with "spot-free" rinse several times the past few months.

Ok, so over the first few months of summer I was noticing that my "normal" operating temp was 190. No real alarms there. It would hold steady at that temp. But, as July arrived and brought the 100 degree days we know so well here in TX, I started seeing the operating temp rise during "load". It would climb to 195 and then drop back to 190 when not on the gas.

Now, it climbs pretty quick to 198-200 when under any kind of load, but drops to 188-190 when coasting. This happens whether it's 107 degrees in the middle of the day or 85 degrees in the middle of the night. The moment I get on the gas at all, the temp steadily rises. I've seen as high as 205 before (long, shallow hill at night in West Texas). I have burped the system a few additional times as a precaution. Required very little coolant (if any).

I drove in CO back in July. The engine would stay 188-190 on steep off-road trails with the engine under load as long I was in 4Lo. If I was 4Hi, the higher temps would manifest.

So, last night, I removed the rad cap (engine off) and coolant was at the base of the neck (as it normally is). The overflow was a tad above "low". I started the motor with the rad cap off and the coolant rose in the neck pretty quick until it wanted to overflow. I turned the motor off and waited 30 minutes for the coolant to drop in the neck. Pretty sure that's normal (though I've read people suggesting taking the cap off, turning on the motor and observing if the coolant is flowing). I check the fan as well. I manually attempted to "spin" it. It would rotate about 1/8-1/4 of a turn before stopping. There was a little resistance when attempting to spin it. Again, pretty sure that's normal and my fan clutch is fine.

At this point, I'm at a loss. I could chalk up the temps to higher ambient for a short while. Heck, I could even chalk it up to the rig being loaded. But, I'm in daily drive configuration the last month and the temp rises anytime I'm on the gas (even just a little). It seems to really spike quick once I hit 55mph. Any speed above that accelerates the temp rise quicker. Part of me is thinking back to the dealer and wondering if A) they put the t-stat in incorrectly (jiggle valve oriented down) or B) they didn't replace the t-stat at all, but said they did (they have a TERRIBLE track record with me r.e. honesty after replacing my steering rack and then saying my coolant was "trapped" in the heater core to explain why there was no coolant in my radiator). Seems odd though that at idle, my engine runs steady 188-190 and fan changes speed from time to time and the aux fan kicks on as normal.

Thinking it's time to completely flush the coolant (5 months old), replace the t-stat and o-ring and then refill again with Toyota Red (mixed 50/50 with distilled water) and then burp the system all over again.

I see 184 to 187f all day long in all stock 98-02 2UZ LC &LX470, between 5,000 and 8,500 feet above sea level. With old factory radiator, new OEM and CSF. All with side and top foam in place. I hit 190 F with both A/C on with OAT of 97F in sunny, stop on go traffic, on black top, but just touching 190 and back off.. @abuck99 can give good temps ranges, for a built rig, they do run higher. Those are temps cursing or in stop and go. Pulling a load you may jump up higher while doing so!.
Temp jumping at higher speed could mean coolant moving either to fast or too slow through system.
Cylinder head temps to high (lean condition).
Clogged radiator fins or radiator.

A few suggestions.

Remove thermostat, checking that jiggle valve is up. Then test in boiling water that it opens as FSM outlines. Replace if not to spec. In any case, replace it's o-ring seal.

If you didn't do the coolant system flush yourself, you may want to redue. Drain the block and radiator three times, filling with distilled water, bring to op temp each time before draining. Then add Toyota LL (RED) and distilled water at 50/50 mix. Remember about 1 gallon of water will remain in system with rear heaters. A little less without. I measure what comes out to know. I then add 1 gallon of 100% red, knowing about 1 gallon of 98% water remained in the system. Then premix next ~2 gallon red & D water 50/50 and add.
Topping and burping over next few days. By running engine at 2,500 RPM (best done driving) with cabin heaters set to hot, for at least 5 minutes after reaching operating temp. Park overnight with front end higher than rear end. Remove radiator cap in morning while cool OAT and out of the sun. Make sure radiator is full. Do each morning until it will not take any more coolant.

Check your timing belt tensioner. Weak, it may allow slippage on water pump at higher speed.

Check head gasket 360* around head the heads.

Check your transmission fluid level.

Notes:

We're seeing some unusual engine temps stuff this year. We may have bad fuel around. "They" may add extra ethanol to boost cheaper low octane fuel. Then they can add water, which ethanol displaces. Result we run lean, as inject are limited how much can pass through them. I just did a fuel pump replacement. Did not help get temp down. But I saw water in the fuel pump. About 20% water. That I've never seen before. This one running hot, we're still working to get temp down. One thing strange I noticed on it day it came to me. The radiator support is too hot to touch, all the way to fenders. It may be a bad radiator, so we're going to try a new one (radiator).

Watch you fuel trims, for signs of engine running lean. A weak fuel pump at high speeds may not delivery needed fuel or clogged fuel filter can act the same. If you see short term - by more than 5% and long term may be + over 5%. You may be running lean.

Run BG 44k through the gas tank. Which may improve Fuel follow.

You may also need to check back pressure of CATs.

Your compression is balance. But it is low. If test was done as FSM outlines, hot engine . That would indicate low compression a "loose engine". Loose engines run cooler and very often rich. So not like the issue of running hot. If that test was done cold, the yours is about what I see, when doing on cold no-op engine. If engine inpo we've no choice. But to get a good reading, you must do hot, fuel cut off, throttle body open and a strong battery.

 

[geanes]

How old is the radiator? Can you inspect the core through the radiator fill cap?

The amount of ethyleneglycole (coolant) changes the physical properties of the solvent, which is water. Adding a solute to a solvent will lower the freezing point and increase the boiling point of the solution. More solute you add, higher the deviation. The process is called Colligative properties.

Radiator was installed in April. It's a CSF. All of the fins are clean and none are bent. Replaced the upper and lower hoses with OEM at the same time.

 

[geanes]

I see 184 to 187f all day long in all stock 98-02 2UZ LC &LX470, between 5,000 and 8,500 feet above sea level. With old factory radiator, new OEM and CSF. All with side and top foam in place. I hit 190 F with both A/C on with OAT of 97F in sunny, stop on go traffic, on black top, but just touching 190 and back off.. @abuck99 can give good temps ranges, for a built rig, they do run higher. Those are temps cursing or in stop and go. Pulling a load you may jump up higher while doing so!.
Temp jumping at higher speed could mean coolant moving either to fast or too slow through system.
Cylinder head temps to high (lean condition).
Clogged radiator fins or radiator.

A few suggestions.

Remove thermostat, checking that jiggle valve is up. Then test in boiling water that it opens as FSM outlines. Replace if not to spec. In any case, replace it's o-ring seal.

If you didn't do the coolant system flush yourself, you may want to redue. Drain the block and radiator three times, filling with distilled water, bring to op temp each time before draining. Then add Toyota LL (RED) and distilled water at 50/50 mix. Remember about 1 gallon of water will remain in system with rear heaters. A little less without. I measure what comes out to know. I then add 1 gallon of 100% red, knowing about 1 gallon of 98% water remained in the system. Then premix next ~2 gallon red & D water 50/50 and add.
Topping and burping over next few days. By running engine at 2,500 RPM (best done driving) with cabin heaters set to hot, for at least 5 minutes after reaching operating temp. Park overnight with front end higher than rear end. Remove radiator cap in morning while cool OAT and out of the sun. Make sure radiator is full. Do each morning until it will not take any more coolant.

Check your timing belt tensioner. Weak, it may allow slippage on water pump at higher speed.

Check head gasket 360* around head the heads.

Check your transmission fluid level.

Notes:

We're seeing some unusual engine temps stuff this year. We may have bad fuel around. "They" may add extra ethanol to boost cheaper low octane fuel. Then they can add water, which ethanol displaces. Result we run lean, as inject are limited how much can pass through them. I just did a fuel pump replacement. Did not help get temp down. But I saw water in the fuel pump. About 20% water. That I've never seen before. This one running hot, we're still working to get temp down. One thing strange I noticed on it day it came to me. The radiator support is too hot to touch, all the way to fenders. It may be a bad radiator, so we're going to try a new one (radiator).

Watch you fuel trims, for signs of engine running lean. A weak fuel pump at high speeds may not delivery needed fuel or clogged fuel filter can act the same. If you see short term - by more than 5% and long term may be + over 5%. You may be running lean.

Run BG 44k through the gas tank. Which may improve Fuel follow.

You may also need to check back pressure of CATs.

Your compression is balance. But it is low. If test was done as FSM outlines, hot engine . That would indicate low compression a "loose engine". Loose engines run cooler and very often rich. So not like the issue of running hot. If that test was done cold, the yours is about what I see, when doing on cold no-op engine. If engine inpo we've no choice. But to get a good reading, you must do hot, fuel cut off, throttle body open and a strong battery.

EXCELLENT write up! Thank you! I'll make sure to follow the drain/refill process to the letter of your explanation. One thing I didn't do when I replaced the radiator was transfer the foam on the sides. I did add foam along the top though. Do you think the lack of foam along the sides could have an impact? I have been considering running some ducting from the small holes in the bumper to the front of the radiator though to maximize air flow over the fins vs spilling out. I run a Slee skid plate, bullbar, winch with control box mounted on top of bumper and twin 9" LED lights on the bumper as well. I was noticing the higher temps prior to the installation of the winch and the Slee skid plate. I didn't monitor closely enough between the "rack" debacle (dealer failed to refill coolant and let me drive away) and the installation of the new radiator 2 months later. Pretty sure they ran the pressure test cold. That would be the "easiest" way for them to do it. They definitely are a "short-cutting" operation. Can't imagine they replaced the o-ring when they said they did the thermostat. Still thinking they didn't even do the t-stat at all. Should know more by Friday when the new OEM T-stat comes in.

 

[2001LC]

EXCELLENT write up! Thank you! I'll make sure to follow the drain/refill process to the letter of your explanation. One thing I didn't do when I replaced the radiator was transfer the foam on the sides. I did add foam along the top though. Do you think the lack of foam along the sides could have an impact? I have been considering running some ducting from the small holes in the bumper to the front of the radiator though to maximize air flow over the fins vs spilling out. I run a Slee skid plate, bullbar, winch with control box mounted on top of bumper and twin 9" LED lights on the bumper as well. I was noticing the higher temps prior to the installation of the winch and the Slee skid plate. I didn't monitor closely enough between the "rack" debacle (dealer failed to refill coolant and let me drive away) and the installation of the new radiator 2 months later. Pretty sure they ran the pressure test cold. That would be the "easiest" way for them to do it. They definitely are a "short-cutting" operation. Can't imagine they replaced the o-ring when they said they did the thermostat. Still thinking they didn't even do the t-stat at all. Should know more by Friday when the new OEM T-stat comes in.

I do "think" side foam is important. But until day I've one running hot without than install an see results, or better visa versa, IDK.

The mass of iron bumper, winch, etc alone will block airflow and retain more heat. Plus additional weight. But still sounds like yours is build similar to @abuck99.

Thermostat O-ring R&R is just good practice. They may leak if not replaced.

Is you coolant level holding. Or do you need to add?

Tonight I saw something interesting, while cleaning (99LC 250K miles steel bumpers, slider, rack) radiators. The engine was hot when I started washing fins with engine running. As I cooled by washing fins, I shut engine down engine. As I continued to wash rad fins, which cools coolant. The radiator hose collapsed. But not one drop came out of a full reservoir. Bad radiator (minor leak), bad cap, bad hoses, old thermostat, 1/2 gallon low. Running 199F just idling in evening, no sun 85 f OAT.

 

[flintknapper]

I do "think" side foam is important. But until day I've one running hot without than install an see results, or better visa versa, IDK.

The mass of iron bumper, winch, etc alone will block airflow and retain more heat. Plus additional weight. But still sounds like yours is build similar to @abuck99.

Thermostat O-ring R&R is just good practice. They may leak if not replaced.

Is you coolant level holding. Or do you need to add?

Tonight I saw something interesting, while cleaning (99LC 250K miles steel bumpers, slider, rack) radiators. The engine was hot when I started washing fins with engine running. As I cooled by washing fins, I shut engine down engine. As I continued to wash rad fins, which cools coolant. The radiator hose collapsed. But not one drop came out of a full reservoir. Bad radiator (minor leak), bad cap, bad hoses, old thermostat, 1/2 gallon low. Running 199F just idling in evening, no sun 85 f OAT.
View attachment 2416613
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View attachment 2416617

Whole host of problems there. Upper radiator hose collapsing is sure sign that the radiator cap is not working or blockage somewhere between the overflow reservoir and radiator.