Runs Normal With No Thermostat

F

firebiz16

New member
Ive had overheat problems as some of you have probably read from a previous thread.

Today I removed the thermostat and my 95 3.0 ran at almost normal temp, just a little below. This was at idle and driving for about 30 minutes at diffent speeds. Never attempted to overheat.

Let it cool down and put the T-Stat back in, refilled with coolant and the dang thing starts overheating when I drive it less than three minutes. It will not overheat while just sitting and idling.

I replaced the STANT T-stat with the TOYOTA T-stat this morning and it made no difference.

ANY IDEAS???

It is running rough and the timing seems to be off, but I'm pretty sure this is due to the knock sensor code I'm getting.

Thanks
Chris
 
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Your truck is running hot and probably has some bad hot spots.


If your truck is running "normal" with out a thermostat, then it is running hot. Usually, with thermostat in, an effective cooling system will keep the engine at temp once it opens.

Without a thermostat, the engine struggles ( or should) to get up to heat.


That your truck heats up quickly without a thermostat leads me to believe you have an issue in your cooling system that isn't thermostat related.
 
The only thing left is to take it to have the block blown out I guess, to see if there is a blockage, the entire cooling system as been replace.

T-Stat, Radiator, Cap, water pump, belts, hoses, valve covers and flushed three times. With the T-Stat out, you see water rushing through the RAD. Not much movement when t-stat is in, actually spurts out when it gets warm.

If it was a blown HG, wouldn't it overheat to some extent even with the T-Stat out?
 
That is odd. You could have pockets of over heating already without the Tstat out.

You are getting a knock sensor error? Is there any knocking?
 
I dont hear any knocking to speak of, It is skipping though. From what I've read a bad knock sensor or knock sensor wire will cause the timing to be off.
 
Just took the thermostat out again, put everything back together, drove about 15 miles and it runs like it should normally with a T-stat IN. This makes no sense. It reaches normal operating temp and I have good heat in the cab.

Maybe a severe blockage down in the block, doesn't seem to be hurting anything though.

What the heck. Any more suggestions....
 
Well. A severe blockage IN the block will damage your block if it is creating an uneven hot spot.

If you don't have a block.. and whatever gremlin devil has left your truck. YEA!
 
my local radiator shop offers a boric acid flush you should check out local shops to see if that may be something they offer.

in the mean time take your radiator out get some duct tape and garden hose tape one inlet with the hose real tight and crank up the water see if anything comes out the radiator.
 
I would suspect a bad water pump, radiator or fan clutch (is the 3VZE a belt-driven fan engine?)

There may not be a blockage, but something else is likely causing inefficient cooling. The intermittent issue may be caused by differences in local temperature. (I ran my 86' through a winter with no coolant, and it was cold enough outside that I didn't damage the engine... But I wouldn't do that again).

Fan clutches tend to do strange things when they go, where that will intermittently engage and disengage causing odd overheating and overcooling issues.
 
Did you figure it out?

I just did my head gasket and started up the engine. Runs good but havin the same exact issues as you. The top hose gets hot but the lower hose is cold. The thermostat is obviously not opening. Whats stranger for me is that it only gets hotter on the temP guage if i put the car in gear. I changed the heater adjuster, does this have to do with it?
 
Had the same problem with my 85 p/u. Had my rad rodded out and that solved it. Did the whole runaround with the t-stat. If it has high miles yank it n have it recored or rodded out. Rodding pretty cheap (i paid $35). When refilling ur rad park it on a slope facing uphill and make sure ur get all the air bubbles out. Good luck.
 
4runner15 said:
I just did my head gasket and started up the engine. Runs good but havin the same exact issues as you. The top hose gets hot but the lower hose is cold. The thermostat is obviously not opening. Whats stranger for me is that it only gets hotter on the temP guage if i put the car in gear. I changed the heater adjuster, does this have to do with it?
Click to expand...

I've had these problems too! Had a head gasket job, new radiator, t'stat, opens; and it still runs HOT! I'm so frustrated. What can I do next? Is there a blockage? I haven't driven it much cuz I don't want to overheat and do more damage, I can't pay anymore. When I had the problems before the HG job it never ran hot!
Help!
 
JakeInGrayTacoma said:
I've had these problems too! Had a head gasket job, new radiator, t'stat, opens; and it still runs HOT! I'm so frustrated. What can I do next? Is there a blockage? I haven't driven it much cuz I don't want to overheat and do more damage, I can't pay anymore. When I had the problems before the HG job it never ran hot!
Help!
Click to expand...

Jake - I discovered that my problem was that I had switched the head gaskets when doing my HG job. That was my conclusion after eliminating most, if not all, of the probable causes.

Some explanation.. The two head gaskets are nearly identical with the exception of one hole the size of a nickel. This hole is where coolant passes through and if the gaskets are swapped, that coolant hose is blocked. Hence, coolant does not flow through the system. This explained why the lower hose remained cold (with thermostat in).

It may be hard to believe since the only solution to confirm this would be to tear it down again to check whether or not this be the case. I'd say if all else fails and you've eliminated all possible causes, do what you need to do.

Here are some of my threads for reference:
http://www.toyota-4runner.org/3rd-g...-after-new-head-gasket-cant-figure-out-2.html

http://www.toyota-4runner.org/3rd-gen-t4rs/119105-head-gasket-symptoms-starting-show-3.html
 
4runner15 said:
Jake - I discovered that my problem was that I had switched the head gaskets when doing my HG job. That was my conclusion after eliminating most, if not all, of the probable causes.

Some explanation.. The two head gaskets are nearly identical with the exception of one hole the size of a nickel. This hole is where coolant passes through and if the gaskets are swapped, that coolant hose is blocked. Hence, coolant does not flow through the system. This explained why the lower hose remained cold (with thermostat in).

It may be hard to believe since the only solution to confirm this would be to tear it down again to check whether or not this be the case. I'd say if all else fails and you've eliminated all possible causes, do what you need to do.

Here are some of my threads for reference:
http://www.toyota-4runner.org/3rd-g...-after-new-head-gasket-cant-figure-out-2.html

http://www.toyota-4runner.org/3rd-gen-t4rs/119105-head-gasket-symptoms-starting-show-3.html
Click to expand...

I looked at your links and I think you are on to something. I showed your comment to the mechanic who did the job and he told me to leave it at his shop today. This totally makes sense. Because usually when I have started my truck (before the HG job) and added coolant, I viewed the coolant flowing by, also the coolant level would drop (as it circulated throughout the system, OPEN t'stat). The few times I have started the truck (after the HG job) with the rad. cap off it spews it out like a geyser (Something blocking the coolant!) So what now? Do I assist him with the tear down, replacement, installation to make sure its done correctly? Thanks for your advice.
 
JakeInGrayTacoma said:
I looked at your links and I think you are on to something. I showed your comment to the mechanic who did the job and he told me to leave it at his shop today. This totally makes sense. Because usually when I have started my truck (before the HG job) and added coolant, I viewed the coolant flowing by, also the coolant level would drop (as it circulated throughout the system, OPEN t'stat). The few times I have started the truck (after the HG job) with the rad. cap off it spews it out like a geyser (Something blocking the coolant!) So what now? Do I assist him with the tear down, replacement, installation to make sure its done correctly? Thanks for your advice.
Click to expand...

Just curious but do you know if he's going to charge you for the tear-down? If not, I'd say offer a hand in the tear down if you're open to it, especially if you have a good relationship with the guy. It's another 5-6 hours worth of labor he's going to have to do which is usually around $500. And to be honest, if it doesn't turn out to be switched head gaskets, at least he didn't go through the trouble all by himself. If it does turn out to be the switched HG, it's definitely not your fault and I feel any mechanic would make the same mistake, especially if they didn't encounter this before. It's unfortunate that there's no clear caution or warning in FSM or the repair manuals about the that small difference. If he's being a dick about it, different story.

By the way, I also purchased the radiator funnel to try and burp my system thinking there was a huge bubble. It also did not gulp and instead was boiling and erupting "like a geyser" too.

Good luck.
 
4runner15 said:
Just curious but do you know if he's going to charge you for the tear-down? If not, I'd say offer a hand in the tear down if you're open to it, especially if you have a good relationship with the guy. It's another 5-6 hours worth of labor he's going to have to do which is usually around $500. And to be honest, if it doesn't turn out to be switched head gaskets, at least he didn't go through the trouble all by himself. If it does turn out to be the switched HG, it's definitely not your fault and I feel any mechanic would make the same mistake, especially if they didn't encounter this before. It's unfortunate that there's no clear caution or warning in FSM or the repair manuals about the that small difference. If he's being a dick about it, different story.

By the way, I also purchased the radiator funnel to try and burp my system thinking there was a huge bubble. It also did not gulp and instead was boiling and erupting "like a geyser" too.

Good luck.
Click to expand...

Well. I have got to tell you, you were right. I offered to help do the work on my truck at the mechanic's shop. He was delighted that I came. He and his employee had business to tend to Friday as I worked on dismantling my engine. As I reached points unknown, I asked for help and continued tearing down. I reached the cam shafts, removed them, and then finally the head ad the gasket. Luckily I had a gasket from the package still and kept referencing your picture and dreading the sight of the gasket. Sure enough I pulled the head and lo and behold the gasket was plugged!! I grabbed the new one which matched correctly. The employee was shocked it was like that (and didn't admit fault) he said, "Oh look it goes right down to the thermostat!" Well duh! That's what was plugged! I was glad to discover what you said was correct! It was plugged! So today his employee set the gasket, head, cam shafts, and the rest of assembling was left up to me. Monday morning I'm going to finish with the belts, fan clutch, and radiator. Thank you!!

You can see in the pic, the gasket they installed which plugged the nickel sized hole and the correct gasket WITH the correct hole. They both exclaimed, "The didn't label the gaskets L or R! Well, it's not rocket science to line up holes."

I'm just glad it's done. Again, thank you! Here's to a cool running engine!!
 

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