Overheating question for the gods!!!

[calinaki]

Alright,

Hat's off to anyone that can properly diagnose this one. Haven't found any solutions on this site for what ails my 1995 4Runner.

So I know the 3.0 V6 (3VZE) sucks and has lot's of cooling issues but here we go.

As I pull up to a stop light after driving on the hwy, the temp rises just up to the red. If I rev the engine, it get's the fan and water pump moving faster and brings the temp back down. Here's what I've done in my quest to solve this issue:

Flushed the cooling system, New Radiator and cap, new thermostat, new fan clutch, and when I bought the rig last year, it had a new head gasket (exhaust/driver side only), timing belt, and water pump. I've had the front end extremely high in the air and have tried over and over to get any air out of it and believe that it's all out. I don't blow white smoke, there's no oil in the antifreeze, no gunk under the oil fill cap, and I'm not using any antifreeze except for some water that slowly boils off after it gets hot and I shut the thing off.

So,... why the overheating when I roll to a stop?

Oh, and the fan blades are good and the factory fan shroud is installed and in good shape.

Thanks, Thanks, Thanks for any help!!!

 

[Bad_Vision]

your getting heat soak it happens when you run at high rpms and then you dont get enough cold air in the radiator to cool it down.
my best option for you is to convert to a electric high output fan.
the not so best option is to put in hood louvers and wrap the exhaust manifolds.
last ditch option is to put some money into a aluminum radiator and free flow exhaust.

 

[SV_Dude]

It sounds like you have a completely new cooling system. What mixture of coolant did you use?

Also, what does the front of your radiator look like? Is it clean or is there any dirt stuck in the cooling fins?

 

[calinaki]

Ah yes,... forgot to mention that I checked the fins on the condenser and they're really in pretty good shape. I also sprayed them out with a hose and made sure that there weren't a significant amount of fins bent over. I also did the flashlight trick.

I used a 50/50 mixture. I actually threw in 100% (half the capacity) and then added the water after the fact. I also tested it and it's rated to about -30 or so.

I'm wondering if there could be an issue with the temp sensor or maybe some sort of blockage in the engine that would cause limited coolant flow through the engine???

Anyone know of an easy way to do a flow test? I suppose the mechanic could've said they replaced the water pump but didn't.

 

[calinaki]

your getting heat soak it happens when you run at high rpms and then you dont get enough cold air in the radiator to cool it down.
my best option for you is to convert to a electric high output fan.
the not so best option is to put in hood louvers and wrap the exhaust manifolds.
last ditch option is to put some money into a aluminum radiator and free flow exhaust.

Is "heat soak" something that occurs due to some degradation of the system??? I can't imagine that this rig did this when it was brand new. My 1982 toyota 22R doesn't do that and it's in much worse shape. Thought about converting to an electric fan but that seemed like a band-aid to the problem?

 

[SV_Dude]

If your cooling system was flushed then you wouldn't have any blockages in the engine. The water pump may be going out and not pumping enough coolant while at a lower rpm or an idle.

Upgrading your fan and radiator is a decent option but these 4runners never had these issues from the factory so there is an issue somewhere. This issue can be fixed without having to upgrade your cooling system.

Once you come to a stop, how long does it take for the engine to heat up? I would pull your thermostat and test it in some boiling water and see if it opens completely. Maybe you have a bad thermostat that isn't opening all the way?

 

[SV_Dude]

Is "heat soak" something that occurs due to some degradation of the system??? I can't imagine that this rig did this when it was brand new. My 1982 toyota 22R doesn't do that and it's in much worse shape. Thought about converting to an electric fan but that seemed like a band-aid to the problem?

Agreed! See my above post. Upgrading your coolant system isn't the fix because you're not doing anything out of the ordinary with your 4runner. If it was a race car that was always at a very high rpm then this would be different.

 

[calinaki]

If your cooling system was flushed then you wouldn't have any blockages in the engine. The water pump may be going out and not pumping enough coolant while at a lower rpm or an idle.

Upgrading your fan and radiator is a decent option but these 4runners never had these issues from the factory so there is an issue somewhere. This issue can be fixed without having to upgrade your cooling system.

Once you come to a stop, how long does it take for the engine to heat up? I would pull your thermostat and test it in some boiling water and see if it opens completely. Maybe you have a bad thermostat that isn't opening all the way?

When I come to a stop, it slowly rises and goes from normal temp (just below halfway) to the cold side of the red probably within 6 seconds or so. The I replaced the thermostat when I replaced the radiator but I suppose it could be bad--I didn't do the boiling water check before I installed it assuming it was good. Seems like if it wasn't opening all the way however I would have overheating issues on the hwy also? maybe not.

Thanks for the responses, I might have to pull the water pump one of these days and make sure it's all there. (not looking forward to doing that to find a perfectly good water pump though) Cripes!

 

[Footofgod]

Where did you get your thermostat? Get an OEM one directly from Toyota. The parts store ones can often be crap.

 

[hoe_nah]

Thermostat installed backwards? Double check your rad cap ive seen "brand new" ones be faulty

 

[mikebontoft]

lately it doesn't matter where you get parts from, they've been junk. wouldn't surprise me as I've changed out multiple failed thermostats, cooling fans even a seized AC compressor that was seized before installation.

have you removed any shrouding or trim from the front end?

 

[willyt4r]

cavitating bypass hose(s)

A plausible explanation of effects of a heat soak would be the condition of one or more of the by pass hoses. I have personally seen and can attest that an old hose puckers at the bend while less volume of coolant is flowing through it. The constraint of the volume of coolant could very well be the culprit in this scenario. :

 

[Jonny]

Electric fan is an awesome mod if you have the spare time and a few extra bucks :fro:
I did the ford taurus mod and been runin cool since in tripple digit heat + AC blasting away..
I do notice my temp rise a little once I get off the highway but you see the voltmeter drop a little as the fan kicks on and the temp drops surprisingly quick.
Not the easiest of tasks however...think it took me about 10-14 or so hours working alone and replacing the thermostat, radiator, coolant flush, mocking up and trimming the taurus fan, wiring the hayden controler, trouble shooting a faulty relay, tracking down a power lead for the AC override (runs the fan constantly while the AC is on), + burping the system the next day and tucking up the wires.

There are a few "all in 1 kits" out there with everything you need but I am too cheap for that.
Breakdown (in my case)
taurus fan $28 from pick a part
Hayden electric thermostatic controler: $45
New coolant: $ can't remember off the top of my head
burp and burp and burp the system some more on an incline.
Think I did mine 5 times @ 15 min per burping session imp:

 

[Bad_Vision]

heat soak is what happens when the block soaks in the heat of the combustion chamber and sense you dont have a ton of air room around the block it stays heated.
upgrading the fan will fix this issue because the fan will run at high rpms all the time and not dependent on the engine to rotate air.

 

[Diverse4runner]

1. Check all hoses for kinks or protrusions(bulges in the hose)
2. Check the T-stat
3. Clutch fan- When it gets hot and you give it some gas, the fan should howl pretty loud.
4. After T-stat burp the hell out of it.
5. Radiator cap. (Mine would not sit flush with the Radiator and would cause spikes in temperature because without pressure the water will boil at a lower temperature) I got mine at Discount Auto Parts= Bad idea. Went to NAPA for a new one now it stays cool.

Did you do the water pump install? While testing you don't have to use 50/50 mix just use distilled water.

P.S. Do you get any sweet smell from the exhaust.

 

[77'911]

Alright,

Hat's off to anyone that can properly diagnose this one. Haven't found any solutions on this site for what ails my 1995 4Runner.

So I know the 3.0 V6 (3VZE) sucks and has lot's of cooling issues but here we go.

As I pull up to a stop light after driving on the hwy, the temp rises just up to the red. If I rev the engine, it get's the fan and water pump moving faster and brings the temp back down. Here's what I've done in my quest to solve this issue:

Flushed the cooling system, New Radiator and cap, new thermostat, new fan clutch, and when I bought the rig last year, it had a new head gasket (exhaust/driver side only), timing belt, and water pump. I've had the front end extremely high in the air and have tried over and over to get any air out of it and believe that it's all out. I don't blow white smoke, there's no oil in the antifreeze, no gunk under the oil fill cap, and I'm not using any antifreeze except for some water that slowly boils off after it gets hot and I shut the thing off.

So,... why the overheating when I roll to a stop?

Oh, and the fan blades are good and the factory fan shroud is installed and in good shape.

Thanks, Thanks, Thanks for any help!!!

What type of rad did you use? The 3vze needs to have a pretty serious unit in there(ie 3 core). The factory has even upgraded the unit from the original that was in our 1990.
regards

 

[calinaki]

lately it doesn't matter where you get parts from, they've been junk. wouldn't surprise me as I've changed out multiple failed thermostats, cooling fans even a seized AC compressor that was seized before installation.

have you removed any shrouding or trim from the front end?

I removed the fan shroud when I changed the radiator but installed it all back the way it was.

 

[calinaki]

Thermostat installed backwards? Double check your rad cap ive seen "brand new" ones be faulty

The rad cap I used was one of those that had the lever on top to manually release pressure into the expansion tank so you can remove it while it's hot. When I would park and turn off the engine after it got hot, I would often hear bubbles into the expansion tank. I assumed it was water boiling out of the 50/50 mix that was stagnant next to the engine block. Granted, I wouldn't have bubbles unless I had some water boiling off but maybe the radiator cap isn't holding enough pressure in the system?? Anyone have a link to a good OEM cap I can buy online?

 

[calinaki]

A plausible explanation of effects of a heat soak would be the condition of one or more of the by pass hoses. I have personally seen and can attest that an old hose puckers at the bend while less volume of coolant is flowing through it. The constraint of the volume of coolant could very well be the culprit in this scenario. :

And here's where I show my ignorance. Where is the bypass hose and what is it for??? I've replaced both radiator hoses at the inlet and outlet. I figured all other coolant passed through the interior of the engine and there were no more hoses involved.

 

[calinaki]

1. Check all hoses for kinks or protrusions(bulges in the hose)
2. Check the T-stat
3. Clutch fan- When it gets hot and you give it some gas, the fan should howl pretty loud.
4. After T-stat burp the hell out of it.
5. Radiator cap. (Mine would not sit flush with the Radiator and would cause spikes in temperature because without pressure the water will boil at a lower temperature) I got mine at Discount Auto Parts= Bad idea. Went to NAPA for a new one now it stays cool.

Did you do the water pump install? While testing you don't have to use 50/50 mix just use distilled water.

P.S. Do you get any sweet smell from the exhaust.

Hmmm,... I took a good sniff of the exhaust when I started it after sitting all night and didn't necessarily smell "sweet". The exhaust looked kinda "white" but I think that's because it was a very cold morning in Western Montana.

The reason I was thinking that there could be a blockage in the engine somewhere that was backing up hot fluid at the temp sensor is because I actually don't hear the fan roar up when the engine shows to be hot--so I'm thinking the heat that is being read on the gauge is not actually making it out to the radiator to affect the fan clutch thermostat. (The fan clutch is new, so again, I'm forced to assume it's not faulty.)

Oh, and I didn't do the water pump job myself. The previous owner had it done and I have the receipt to prove that he at least paid for the labor.