Still Overheating (Passed block test)

T

the1998sr5

New member
SO I'm still overheating. This is happening on my drive home from work. After about 20 minutes of highway driving I drive through traffic for the last leg of my journey. It does not do this everyday, but I'd say 2 out of 5 days- always at the very end of my trip. I throw the heat on and it cools back down.

New: Radiator, Thermostat, new Asin fan clutch, hoses, flush, new toyota red coolant plus water wetter, complete new exhaust, new air filter.

I just had it block tested several times hot and cold and it passed no problem. Also had it compression tested, I do not know the exact numbers, but it was good.
At 182k, did timing and water pump at 145k.

I feel like I'm running out of ideas here......
One mechanic suggested engine sludge- I'm totally skeptical on that one.
The girlfriend dose not like when I need to put the heat on (and its 90 degrees out)- I do not want to have to choose between them :)
 
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Try a new OEM radiator cap.

Did you use an OEM thermostat?

Also make sure as much air as possible is out of the cooling system. This cooling system is not the easiest to burp so to speak.
 
Thanks, I should have mentioned I have a new Toyota Radiator cap. All the parts I have replaced have been OEM.

I burped it with the front wheels on a 10 inch incline, for about 1/2 hr. cycling heat on and off.

What do you think?
 
Ok. It sounds like your have covered most areas. Having to add any coolant as jeremyc74 asked?

It almost sounds as if the fan clutch is bad. Can you hear it come on when you start the 4runner and when it is idling? With Hayden being made in China now I have had many over the counter clutches be bad right out of the box. Don't know about Aisin.

Do you have a Scangauge or the like that can read live data? I'd be curious to see what readings the ECU is seeing from the ECT when it is running hot.
 
I hope you can find it. My talon before partout was doing same thing. Rebuilt motor, all new oem parts, radiator, extra slim fans, everything was done. I always just thought it was my 4" thick intercooler and the 400whp. I could never figure out the overheating.
 
honestly you are idling in extreme heat (90+car heat) in an older car

Maybe the fan is not good enough in that context the electric fans now have more cfm

What kind of radiator?
 
c0mmon said:
honestly you are idling in extreme heat (90+car heat) in an older car

Maybe the fan is not good enough in that context the electric fans now have more cfm

What kind of radiator?
Click to expand...


90 degree heat in an older vehicle means nothing. You shouldn't overheat just because it's warm outside.
Op I would burp the coolant again. Make sure to turn on the rear heat as well if equipped. Then I would replace the thermostat again. And the rad cap Just because it's cheap and easy.
 
Have you tried pressure washing the fins on the radiator? Might be full of crud from over the years.

As for idling in hot weather in extreme heat, it's a 100* here and mine idles fine (knock on wood) with no over heating with the AC cranking on what I'm certain is the original fan clutch and an engine full of stop leak.
 
c0mmon said:
honestly you are idling in extreme heat (90+car heat) in an older car

Maybe the fan is not good enough in that context the electric fans now have more cfm

What kind of radiator?
Click to expand...

1996 with 260k miles. New radiator. I have never overheated once since owning and have driven 90-100* weather many times.

Now after saying that, this has really been my only car that has never overheated on me. Knock on wood!!
 
c0mmon said:
honestly you are idling in extreme heat (90+car heat) in an older car

Maybe the fan is not good enough in that context the electric fans now have more cfm

What kind of radiator?
Click to expand...

It gets 115+ out here and my truck is black but doesn't overheat. There are nights where it doesn't even make it down to 90.

I'm wondering if the computer is saying its overheating or if it actually is overheating. Maybe try to install a separate temp sensor to see what the numbers are and if it matches up with the computer.
 
I just want to add this. Just because something has been replaced (even with OEM) doesn't mean it works properly or even at all. Brand new parts fail — yet still appear new and functional.
 
Reading through the posts... I see

Radiator - replaced (what brand? from where?)
Hoses - replaced
clutch fan - replaced
coolant - replaced
t-stat - replced
timing belt - replaced 37k ago
water pump - replaced 37k ago

I'm honestly guessing it's the timing belt sliping on the water pump pulley, cause I had this on a 40k mile timing belt... WP was still good, but it was slipping on pulley which didn't pump water.

it could also be your clutch fan.

it might actually be your 'AC radiator' or condenser (or is it evaporator? the one in front of the rad), possibly your AC system is working too hard and making your engine over heat... check your AC system for correct pressures, heck I would just flush it and re-do the Freon at a professional shop.

Also, check your fuel filter, if never replaced that's 17yrs of gunk, think of a pump getting gas through that.

BTW 115 summers here in AZ... I don't have any issues with good working parts (only issue I've had is where parts aren't working lol go figure)
 
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Wow lots opinions on this one!

No [Toyota] engine should ever overheat just because it's high mileage. Even the garbage V6 engines in the pre-96 4Runners didn't overheat without reason.

The good suggestions to check here are the water pump and the cap. Be sure it's the exact cap for your engine, if the PSI is off then it won't hold pressure as it should and will start to boil/overheat. To check the water pump function, take off the radiator cap on a COLD engine and start it up. If you do this when hot you'll get scalded with 200+ degree coolant so please don't do that. Let the engine warm up and as the thermostat opens, you'll start to see fluid flowing through the radiator as it cycles through the engine via the water pump. If this does NOT happen, something is wrong with your water pump and is the cause of your overheating.

The water pump theory could be your issue. Ambient air from the moving vehicle and fan could be enough to keep the engine cool at first but if the pump isn't working you'll have issues once the truck slows down or idles for any prolonged period.

Reason why I don't think it's the thermostat is because there's nothing really to go wrong with a thermostat. You can pull it and dump it in a pot of barely boiling water for peace of mind if you want and it should open just fine, but I've never seen one not open when new or in any usable shape. It's generally pretty obvious if you have a bad one.
 
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Mgyver1 said:
It gets 115+ out here and my truck is black but doesn't overheat. There are nights where it doesn't even make it down to 90.

I'm wondering if the computer is saying its overheating or if it actually is overheating. Maybe try to install a separate temp sensor to see what the numbers are and if it matches up with the computer.
Click to expand...

Do you have New Jersey traffic?
 
1stly, Thanks to everyone for your help. I'm sorry it has taken me a day to respond. To acknowledge everyone's inquiries:

Radiator - replaced (what brand? from where?) Koyo- recommended from yotatech forum
Hoses - replaced
clutch fan - replaced
coolant - replaced
t-stat - replaced
timing belt - replaced 37k ago
water pump - replaced 37k ago
-jiggle valve at 6
-new exhaust from manifold back

It’s definitely overheating, I take this seriously pull over and check to see coolant boiling and rising in overflow tank. I also do not drive it till it cools down, I’ve never let it get too close to the red zone.

It’s not losing any coolant.
Fan clutch roars and passes magazine test (also is brand new).

*Leading hypothesis's as of today:
-perhaps slipping water pump belt? bad tension-er?
-Someone asked about fuel filter, it has never been changed- perhaps this is a good idea? How about fuel pump?

-I have had a few people suggest transmission getting hot- explained that trans dumps a lot of heat into radiator, even more so during stop and go
( I have an amazon gift card and I'm thinking about getting an external cooler)
Trans oil is dirty, not burnt, but dirty, also shifts fine (haven't changed it due to fear of slipping after, last owner did not know when it was changed and he had it 10 years!)
-my radiator fins and AC condenser fins are clean
What should I do next??
 
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The next question is whether or not the tensioner was replaced with the TB/H20 pump. If there isn't enough tension on the belt to drive the pump fast enough then that could be a problem. I saw such on a Honda Civic not too long ago. The tensioner was maxed out, didn't keep enough tension on the pump and ultimately a bad head gasket occurred though the OEM pump itself and the OEM belt were fine.

No bubbles in the coolant until it becomes hot correct?
 
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