Troubleshooting Overheating - What Next?

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Aug 23, 2021
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While I agree that it is good to fix the radiator shroud - I do not think this is your issue, especially since it has been like that for a while. If you have a working fan, and enough water flow I don't think you would have an issue in the state you have it.

I have run cars, granted, not LCs with no shroud at all with electric fans because of clearance (engine swap in a CJ7 and a YJ), and for a while I had the fan straight wired for trail rides and I could not get it above 180 not matter what I did.

This seems like an air flow issue, but it could be related to engine RPM - have you checked the belt/pulley? Could the belt be worn or under-tensioned and slipping so you are not getting full engagement? Could the impeller on the water pump be worn? The higher RPMs may be allowing them to do enough until you hit lower RPMs...and the symptoms would present in a very similar manner.

Just another idea since you are scratching your head. Hope you get it figured out!
 
Joined
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While I agree that it is good to fix the radiator shroud - I do not think this is your issue


This seems like an air flow issue,

Yeah but there are more reported cases of dirty radiators causing these symptoms then intermittent water pump failure.. Makes sense on paper that it could be a water pump failing but whenever troubleshooting start with the simple s*** first. These forums have a way of making people want to rebuild every part to fix their problem.

- Checking for proper coolant level in the res and in the radiator is first up
- Then the missing shroud and dirt build up should be addressed. If it doesn't do anything to help then you can move deeper down the troubleshooting tree.

I agree belt tension and condition should also be checked since that's a quick and easy thing to do. While checking stuff like that you can feel the fan clutch but it was noted the OP thinks it's operating fine ( since it was hard to spin by hand when warm , assuming the belt was off)

After that I suppose things like system pressure, water pump operation, etc. can be considered.
 
Joined
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Austin, TX
Thanks ya'll. I appreciate the feedback.

With a clean radiator in place, I think my next thing to dive into is the fan clutch even though initial testing looks okay. It seems like an airflow issue best I can tell.

Since the engine cools at speed and the radiator hoses are hot, would that not indicate that the water pump is functioning? Unit is about 58,000 miles old.
 

JunkCrzr89

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With a clean radiator in place, I think my next thing to dive into is the fan clutch even though initial testing looks okay. It seems like an airflow issue best I can tell.
This is on a 4runner but the same testing procedures apply to the 100. Start at the 5:00 min mark. @Timmy65 does a great job walking you through the steps to test if it’s functioning properly or not.

 
Joined
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Hi incudie,

Have you seen any evidence to corroborate your temp gauge in the cluster? On my MR2 the 'temp. sender' sensor went bad which gave false information on the water temperature gauge.

Also, now that my '99 is over twenty years old, I'm starting to wonder if it's about time to test the OE cats. If they're getting clogged that will create a lot of heat that could very well create negative effects throughout the vehicle systems. > https://www.youtube.com/watch?v=qJTmddbOxMk
 
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Hi incudie,

Have you seen any evidence to corroborate your temp gauge in the cluster? On my MR2 the 'temp. sender' sensor went bad which gave false information on the water temperature gauge.

Also, now that my '99 is over twenty years old, I'm starting to wonder if it's about time to test the OE cats. If they're getting clogged that will create a lot of heat that could very well create negative effects throughout the vehicle systems. >

OP mentioned specific temperatures so my guess would be he has a scanner providing these temps.
 
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Heating at idle and normal temps while driving = failing fan clutch. Make sure you get an OEM or AISIN clutch. Any other aftermarket clutches are always engaged and will making roaring noise at all times and is really annoying to hear.

Saw you cleaned the cooling fins on radiator, how is the AC condenser and trans cooer fins? Are those clean too?

Does the radiator you replaced has the same thickness as your OEm unit?

Buy AISIN fan clutches from a reputed shop (like rockauto). You said AISI (not an AISIN product unless it is a typo)
 
Joined
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Austin, TX
Fan clutch is AISN and replaced 58k ago. Other fins are clean as well.

Radiator is aftermarket on rock auto. Aluminum. Has worked fine up until recently. No visible issues as far as I can tell.

Thanks for the link @JunkCrzr89
 
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Fan clutch is AISN and replaced 58k ago. Other fins are clean as well.

Radiator is aftermarket on rock auto. Aluminum. Has worked fine up until recently. No visible issues as far as I can tell.

Thanks for the link @JunkCrzr89
Assuming you checked over all the basics I'm sticking with a fan / air flow problem.

Don't over think it, you're on the right track. Many other people on these forums have had similar issues with the fix being radiator / fan air flow related.
 

JunkCrzr89

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Assuming you checked over all the basics I'm sticking with a fan / air flow problem.

Don't over think it, you're on the right track. Many other people on these forums have had similar issues with the fix being radiator / fan air flow related.
x2
 
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Here's a LIST:
(Mike & Junk both hit a really important issue, each!
1-Get that other half shroud & install.(Junk)
2-I'd resist 1st instinct to replace fan clutch(Junk & Me, fyi, it shouldn't stop turning <1second when shut off when HOT....that's not right, should be 2-3 seconds, but if still locked up Your clutch is fine, move to the next possibility)
3-Drain (& Save) coolant. If it looks good, You can strain it thru coffee filters poked in a big funnel from catch basin back in to jugs.
3-Get a couple bottles of radiator (& Block) flush, add w/water, run them thru whole system while keeping enough fresh water flowing thru block & radiator drain to maintain full level; Or
4-BOIL OUT radiator (either above radiator flush or take to radiator shop & have them boil out & pressure test), while they're at it they always wind up cleaning exterior fins, which is best done if that was Your only issue, w/a can of "Air Conditioner Condenser Unit Cleaner" which can be had at any major hardware chain, spray it all over, follow directions & wash it off GENTLY (I've seen folks take spray nozzles so powerful they dissolve fins, & Yours looked Pretty Dirty from back side? [If they're dirty on back side, no air is making it thru from Front side? Using it on A/C Condenser & Transmission cooler is a real good idea (ok, so, get 2 cans of that stuff & use 1 just on Trans Cooler & A/C Condenser; other on the back side of that radiator's fins, multiple cleanings. Incoming cooling air has to get past Both A/C Condenser & Trans Cooler to get To Your Radiator. See where Your temp holds after all the cleaning.
5-Did You check/change/possibly damage Block Coolant Temp Sensor? Wouldn't it be ironic if all Your 'paranoia' was caused by a faulty sensor?(Mike's idea)
6-Just because You can, I'd change Water Pump. Yes, we all read it was new 54k mi. ago, & well, every now and then we all get a 'lemon', You might have too.
Warping Heads &/or blowing a head gasket, over a super heated block is a much more expensive fix than that new water pump?

Multiple other 'guru's mentioned what You said is that when at a stop & idle, temp is spiking...that can partially be due to missing shroud section but I'll bet a dollar it's Water pump/serpentine belt, seen it 2 many times. Lower rpms has it not moving enough coolant. Yes, Austin IS Hot as Hades this time of Year, but there are a few legit reasons You've got these issues; most aren't pricey fixes. It can Easily be several issues combining (along w/100+F ambient temps) Did You test Water Pump Bearing? (Grab fan & see if there's even Slightest wobble/movement fore & aft at fan blade tips....anything more than blade flex...yes, kicking on Heat moves more coolant, but that doesn't confirm Your pump is at 100% & IF bearing is going. slightest movement out at ends of blades will show the 'wobble'.

Any 'squealing' or belt noises? These are usually telltale for either water pump/belt or fan clutch issues. Both water pump & Fan clutch should be targets AFTER all that cleaning (Especially since OEM Thermostat was just replaced).

1 thing for certain....Your Replacing Starter, intake manifold & injectors had Nothing to do with this. Obviously neither did heater inlet/outlet hoses.
1 good thing....You didn't mention loss of coolant? (IF You were losing any, there'd be "caked up PINK Dried "foam" at every leak point, whether clamp, hose, fitting or housing.
Here's a final (potentially scary) possibility referencing head gaskets.....How's Your OIL Look on dip stick? (if it were mine, I'd go look at the stick RIGHT NOW, if it's creamy looking like coffee, at least 1 of Your head gaskets already blew & that's Your cause for overheating(But this always includes loss of coolant)? Generally this has a dead giveaway of massive amounts of steam at exhaust, it's hard to miss, but not always....the dipstick never lies. Temps at 240 if they happened or happen again, can lead to this failure, so screw the a/c, no matter how hot it is outside, before messing up Your engine in a daily driver, Flip that Heat & defroster to High when stuck at lights if temp starts spiking badly again?

Radiator boil out is usually $35-$50. if You take in to them, Water pump = $100. & Fan Clutch abt. the same. Condenser Cleaner is $8.-9. a can & Prestone or Zerex Radiator Flush is abt. $8. a bottle. Water's in Your hose and this isn't life altering....probably couple hrs of cleaning & You're going to be fine...I'd stay way from using brushes on radiator fins, condenser fins or trans cooler fins; just cleaner, then wash off w/water, 2-3x let it dry & compare to Your picture. same for radiator flush. We've all seen all kinds of 'gunk' come rolling out radiator drain doing flushes & that crap was clogging Your coolant channels in block, clogging up radiator, & generally stopping flow, everywhere. Be sure to have heater on when doing flushes & follow directions exactly. When done, You' should be able to notice even under hood that it's running cooler; turned off, drain out all the water, close radiator drain, add coolant back in & You should be fine. Dirt is the enemy of airflow. Whether filters or intakes or cooling systems, they have to be clean to work well.
HTH's?
 
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Joined
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Deep Creek, Florida
I was able to purchase new foam recently although I stuck it to my oem skid plate . Suppose it would have made more sense to stick it to the frame above.

I can't imagine what you would have screwed up with your starter job they would be making this happen. If something is leaking you would see it and the fluid level would be low. What else might have happened , aren't there some electrical connections down in the engine valley related to cooling ?
Actually the foam is still on ours (at the top front front of the Skid Plate. It looks to be 3" wide & abt. 2" tall. So multiple layers of window/door/truck camper shell peel & stick would work pretty good?
 
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Actually the foam is still on ours (at the top front front of the Skid Plate. It looks to be 3" wide & abt. 2" tall. So multiple layers of window/door/truck camper shell peel & stick would work pretty good?
Oh nice, so being on the skid plate is the way to go. I suspect that type of basic window foam wouldnt hold up . The Toyota foam takes some abuse. Always removing and replacing them skid and all the water and grime it's exposed to.

I actually just replaced mine like last year so the OEM is probably still available
 
Joined
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Austin, TX
I fixed this late June. Fan clutch was the likely culprit. Someone above asked but I was getting the coolant temperature through OBDII.

I messed with the clutch oil and open/close settings on this new AISN blue hub clutch for fun. I couldn't tell you if it made any real difference but I'm running cool now and never go past 194* when idling for 30m and blasting the AC in 110* Texas heat.

On to other maintenance tasks :)
 
Joined
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Oh nice, so being on the skid plate is the way to go. I suspect that type of basic window foam wouldnt hold up . The Toyota foam takes some abuse. Always removing and replacing them skid and all the water and grime it's exposed to.

I actually just replaced mine like last year so the OEM is probably still available
Thought You'd appreciate that 'on the front of skid plate is where they put it originally? Agreed, window/door insulation was an alternative, I doubted OEM was/is still available, if so gotta go hunt some down, ours (fm '01) is getting pretty 'crunchy' 👍
 
Joined
Aug 7, 2022
Messages
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Deep Creek, Florida
I fixed this late June. Fan clutch was the likely culprit. Someone above asked but I was getting the coolant temperature through OBDII.

I messed with the clutch oil and open/close settings on this new AISN blue hub clutch for fun. I couldn't tell you if it made any real difference but I'm running cool now and never go past 194* when idling for 30m and blasting the AC in 110* Texas heat.

On to other maintenance tasks :)
Dang, Note to Self, NOTE DATE of posting! Sorry concluded You had aftermarket temp gauge versus 'needle on the dash', So did You ever flush cooling system? It's a good thing to do every few yrs, although Toy's Red Coolant is really good at minimizing scrunge growth? Just rebuilt wife's a/c system(s) & now they're like Yours', ice cold. 110F in August sounds about right! We went to Houston to pick up a Ford Horse Trailer Hauling F350 yrs ago. Got to dealers at 0900 opening time. They still had some wk to do on it before our drive back to FL & they commented, yep, everybody came here to escape the 'TX Heat' for vacations? We thought, what are these crazy fools talking about, it's hot as Hades at home?! By 1pm it was 109F, same Humidity as Here and we were crawling around like worms in the sun desperate to get back inside their A/C Showroom! Walking outside, in the 'breeze' it was like Sticking Your Head in a Convection Oven! Learned our lesson, TEXAS is definitely Hotter than here!:flamingo:
 

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