Well isn't that just perfectly logical. Nice job.
LX470 Heater Function Problem
- Thread starter ItGoesTo11
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- climate control heater sensor
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- Thread starter
- #22
Thanks, yes, that was the issue. It was so confusing because the system was, in fact, "working perfectly". So, mechanically and electronically there was nothing to fix, it was simply low coolant. The vapor lock simply kept coolant out of the cabin heater core.
The issue is resolved.
System is self burping. Just check radiator & reservoir each morning after 8 hour cool down. Top radiator and fill reservoir to cold mark (higher first morning). Then check reservoir to see at high mark when hot. Repeat for three days usually does the thick.
I'm surprised you got any heat when warm, if reservoir wasn't drawing down during cool down. I'd also be suspired if temp gauge got to normal, with coolant low. Gauge will normally read low, with low level of coolant. It the silent engine killer.
You may have been in that sweet spot, but, if reservoir doesn't draw down check radiator cap.
I'm surprised you got any heat when warm, if reservoir wasn't drawing down during cool down. I'd also be suspired if temp gauge got to normal, with coolant low. Gauge will normally read low, with low level of coolant. It the silent engine killer.
You may have been in that sweet spot, but, if reservoir doesn't draw down check radiator cap.
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- Thread starter
- #24
I think the coolant was low enough where it was able to self burp when running (hence heat after I started driving) but prior to morning start the air in the system would rise at night during cool down to the highest point, which is the inlet tubes for the cabin heater core. In the morning at idle it would never heat up, even after 30 minutes. It needed the faster water pump action to overcome the air bubble and push it through the system.
After refilling last night I took it for a drive, with a few acceleration blasts (if you can call it that on an LX470) that raised the RPM above 4,000.
When I got home, the coolant was low again, but not nearly as low as before. I refilled it and this morning before start, it was still full and all heater functions are now normal. I'll check it again each night for a few days as suggested.
The temp gauge is fed it's signal from a different sensor than the engine coolant temp sensor on the 2uz-fe engine, so that gauge was acting normally.
And good call on the radiator cap, the system did not draw down from the reservoir, so I'll replace that too just to be sure.
may be what happened, and i'm just guessing here, when the water pump was replaced and they filled out with coolant, they never opened up the heater, which can take up to an extra gallon of coolant. so when you used the heater for the first time, coolant started circulating thru the core and brought the total level down.
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- #26
I'm confident that's what happened too. They just "refilled" the system (engine & radiator) and figured it was full, but there was air trapped in the heater core. And it wasn't noticeable until winter.
All seems to be well now and hopefully this will save someone time in the future!
- Thread starter
- #28
A bit more than a half a gallon...
That's a lot. Did your heat blow warm, hot or very hot?
I find it interesting the fan ran high (blows full speed) when coolant system low. It's my understanding the cabin fan is control via data from Engine Coolant Temp sensor (ECT) input to ECU then control by relay. I've wondered what Water Gauge Sender is for. Could it be ECU doesn't get signal of water or temp, becomes confused, and allow fan to run...
This cold be a way to help diagnose low coolant level. I usually ask; does heat blow hot. Which is either low level or weak/bad thermostat. Weak thermostat engine runs cold, this can confuse o2's leading to false bad CAT code.
If coolant low, engine overheats, while driver see gauge indicates running cool. Very bad....
1/2 gal would likely put below Water Gauge sender unit & ECT.
Water gauge sender unit & ECT are in my red arrow bottom right, on water bypass:
I find it interesting the fan ran high (blows full speed) when coolant system low. It's my understanding the cabin fan is control via data from Engine Coolant Temp sensor (ECT) input to ECU then control by relay. I've wondered what Water Gauge Sender is for. Could it be ECU doesn't get signal of water or temp, becomes confused, and allow fan to run...
This cold be a way to help diagnose low coolant level. I usually ask; does heat blow hot. Which is either low level or weak/bad thermostat. Weak thermostat engine runs cold, this can confuse o2's leading to false bad CAT code.
If coolant low, engine overheats, while driver see gauge indicates running cool. Very bad....
1/2 gal would likely put below Water Gauge sender unit & ECT.
Water gauge sender unit & ECT are in my red arrow bottom right, on water bypass:
- Thread starter
- #30
Thanks, this is a great pic, and it's exactly what the system looks like. It will help future people in need of this advice.That's a lot. Did your heat blow warm, hot or very hot?
I find it interesting the fan ran high (blows full speed) when coolant system low. It's my understanding the cabin fan is control via data from Engine Coolant Temp sensor (ECT) input to ECU then control by relay. I've wondered what Water Gauge Sender is for. Could it be ECU doesn't get signal of water or temp, becomes confused, and allow fan to run...
This cold be a way to help diagnose low coolant level. I usually ask; does heat blow hot. Which is either low level or weak/bad thermostat. Weak thermostat engine runs cold, this can confuse o2's leading to false bad CAT code.
If coolant low, engine overheats, while driver see gauge indicates running cool. Very bad....
1/2 gal would likely put below Water Gauge sender unit & ECT.
Water gauge sender unit & ECT are in my red arrow bottom right, on water bypass:
View attachment 1364068 View attachment 1364069
You are correct, the auto fan is controlled by the relay information from the ECT sensor and it indeed was sensing engine temp, even at low coolant. And the separate Water Gauge sensor does just that!
It's separate from the ECT just for the gauge, it doesn't serve any other purpose.I also found out if the ECU doesn't get signal from the ECT, it will trigger a CEL, then OMG.
The ECT is used by the ECU to alter fuel/air mixture based on engine temp and thus is an "emission control" device. It also has the auxiliary purpose of telling the Climate Control when to start sending heat into the cabin. And they used to say carburetors were complicated!Now...both the ECT and the Water Temp sensors were fully immersed in coolant, even with low coolant. Why? Because the inlet tubes for the heater core are the highest point in the system, very high in fact. (You can see in your picture they shoot straight upwards at the back of the engine like snorkels.) So the sensors were always reading correct coolant temps, which is why this was so hard to diagnose.
In addition, see the downward facing "tee" in the photo just before the small coolant hoses running to the heater core in the firewall? That made it even more complicated because the coolant was "waterfalling" into those hoses and back to the rear heat cabin heater core (the LX470 has two) and the coolant would go there first rather than keep moving uphill.
So, to clarify, the car could never run overheated without alerting the driver and the ECU. But you are correct this is a way to diagnose low coolant level in this vehicle due to the air locking of the main cabin heater core (eg: no heat at idle at first start in the morning before driving)
The fix is, fill the radiator with coolant.
Sorry it is well documented that the 2UZ engine overheats without giving the driver any warning, it is why the TEE fittings are advised to be changed as preventative maintenance as these can kill your engine if they start to weep.
- Thread starter
- #32
I don't see how that's possible given the locations of the sensors in the crossover bypass, the heads would be starved for water by the time that happened. And I can't find anything anywhere to document this issue which you claim is common.
If you have documentation/links/references, maybe post it here so future people in need of the info will have it handy.
I didn't say it was common, just that it is well documented on this forum. I can't defend it from personal experience, I just take other people's word for it. It seems you might be a victim of this, as you had lost a fair amount of coolant and was totally unaware of this, it didn't cause you any other issue other than the blower coming on initially blowing cold air before the engine had warmed up but others haven't been so lucky.
- Thread starter
- #34
Maybe, but I don't think a half a gallon of coolant would cause an overheat, and I live in a mild climate. I also think much of that missing coolant was in the form of air in the main cabin heater core and the engine was perfectly happy.
But all is well now, a top off seems to have solved it. I fault myself for not double checking the shops' work though...I almost always do that.
The shop should of told you to keep an eye on the coolant level for the first few days after the work was carried out as the level will drop and need topping up as the air works its way out.
- Thread starter
- #36
I blame me, I almost always follow up on repairs, even simple things like tire replacement. I trusted the reservoir bottle level and should not have.
Plus, I have an awesome set of tools!
It looks from picture above, that coolant travel from engine to heater core through DS Tee. The DS Tee's is away first to go, falling apart with first pull. Although I've never had this happen to me either, I do have antidotal & written evidence. It's why muder's know to PM the tee's. It the silent killer of the 2UZ-fe. Silent, but not without signs. Like the sweet smell of coolant steam, puddle on the floor or red crusty around the leak. The most notorious one is low temp gauge reading. Killer is a strong word, where it's usually a head gaskets that takes the hit at least in milder climates.
Notice only DS heater Tee was replaced. Conner shop reparing leaks or broken tees don't always replace both Tee's, a PM job surely would. This and swollen hose is indication of overheating.
This is further clue and result of over heating. Can you guess which gasket this is.
Notice only DS heater Tee was replaced. Conner shop reparing leaks or broken tees don't always replace both Tee's, a PM job surely would. This and swollen hose is indication of overheating.
This is further clue and result of over heating. Can you guess which gasket this is.
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Once coolant system burped fully, note temp feel when cabin heat's on high. Does it now feel hotter. The 100 series blows very hot.
If I paid good money to have my rig fix, I'd be pissed. I'd be very concerned of heat damage reducing the life or increasing the cost of engine repairs over the life of it. Life which is document at 1,000,000 miles and counting. If they can't even fill a coolant system, what else can't they do properly. Some issue you may experience from prolonged overheating; early failure of coils, hoses going bad, head gasket, heads, CATs, o2's.
Unlike a leak showing sign you'd have none say possible temp gauge reading a bit low or high perhaps. It' s hard to say unless I pull 1/2 gallon from my system and see. Even then it's difficult as the Land Cruiser temp gauge is not responsive to change as I'd like to see. Keeps owners from worrying I suppose. Also too find if cabin fan runs before warm up.
In case of leak, coolant will eventually get to point where it will not pump into heater core. At some point even expansion will stop raising to point heater core receive. With system just being low, not loosen additional coolant, it may continue getting into heater core or even make to thought pump. Be but run dry even short periods will reduces it's life as well as over heat engine.
The question is how low is 1/2 a gallon. Is it low enough to expose sensors or pump????????????
Book will say keep above fins of radiator.
Normal to slightly low operating temp gauge reading:
If I paid good money to have my rig fix, I'd be pissed. I'd be very concerned of heat damage reducing the life or increasing the cost of engine repairs over the life of it. Life which is document at 1,000,000 miles and counting. If they can't even fill a coolant system, what else can't they do properly. Some issue you may experience from prolonged overheating; early failure of coils, hoses going bad, head gasket, heads, CATs, o2's.
Unlike a leak showing sign you'd have none say possible temp gauge reading a bit low or high perhaps. It' s hard to say unless I pull 1/2 gallon from my system and see. Even then it's difficult as the Land Cruiser temp gauge is not responsive to change as I'd like to see. Keeps owners from worrying I suppose. Also too find if cabin fan runs before warm up.
In case of leak, coolant will eventually get to point where it will not pump into heater core. At some point even expansion will stop raising to point heater core receive. With system just being low, not loosen additional coolant, it may continue getting into heater core or even make to thought pump. Be but run dry even short periods will reduces it's life as well as over heat engine.
The question is how low is 1/2 a gallon. Is it low enough to expose sensors or pump????????????
Book will say keep above fins of radiator.
Normal to slightly low operating temp gauge reading:
- Thread starter
- #39
The 2UZ-FE holds 4 gallons of coolant, so a 1/2 a gallon should not be enough to cause any damage, it did not show any signs of overheating. The pump is far lower than that and the sensors should have been bathe din coolant in the crossover tube, much of the loo was in the heater core itself, it's really high in the system. But I agree with you about the shop, they should have mentioned something.
Adding coolant solved the problem, the climate control system works perfectly now.
You're probably ok, these 100 are tanks and can take a licking and just keep on ticking.
I recall you said cabin heat felt hot. Very hot was the answer I was looking for, but it is subjective.
I've been out all day working on 100's, and don't recall what you may have said about coolant temperature gauge position over last 8 months?