spindleshanks

Is it possible that the radiator is doing such an efficient job as a heat exchanger that the coolant leaving the rad at the bottom hose is actually cool to the touch? Probably not, even on a Toyota...lol

kdawghuntnfish

mt goat
The jiggle valve is a 12 o'clock.

mt_goat

And the T-stat opened for you when you tested it in the pan of water on the stove test huh? Don't guess you measured the temp when it openned and closed did you?

kdawghuntnfish

The termostat open at 180 degrees like it is suppose to.

Slowrunner

My temperature guage reads less than half and has never went past half way.

ovrrdrive

About all you have is a compression test...

Try running it without the thermostat and see what happens. It's not really designed to run like that, but it will definitely rule out it being backwards or not opening.

kdawghuntnfish

Will a compression test tell if a water passage blocked? I will try to run it w/o the termostat and see what happens. I will also try the compression test, anything to rule out the head gaskets installed wrong w/o pulling them. Thanks ovrrdrive

TNRabbit

I just read your entire post and the other one you referenced as well; it sounds like everything is working properly. Is the truck actually overheating/blowing off radiator fluid? If not, I have a sneaking suspicion you have a BAD TEMPERATURE SENDING UNIT. If you notice no evidence of overheating except the gauge, that's what it sounds like to me. How long (in miles) since your rebuild? If it's significant, the head gaskets are on correctly because you would have noticed that problem RIGHT AWAY!

Check the sending unit. That's my bet.

P.S.--I have a '94 3.0 and the only time the water temp has EVER gone past the halfway point was when the water pump failed and blew all the water out of the engine. It got pretty darned hot then...

kdawghuntnfish

TNRabbit. I was kind of questioning the sending unit myself. The engine was was just rebuilt. It was only run long enough to set the timing and test drive it about 5 miles.

I had problems with the oil sending unit and there may be a chance the temp sending unit is bad also. The motor I installed was from a 91 4Runner. It may have had a different style temp gauge since the oil sending unit was different. Im going to be getting and aftermarket temp gauge with actual numbers on it and install it. I don't care much for the white/ red lines the gauge has on it now.

This was a fresh rebuild. It was only run long enough to set the timing and test drive it about 5 miles.

When your pump failed did it push water out the overflow through the radiator cap and out the overflow tank? My truck will not push water out the radiator cap, but it will push it out the top of the radiator with cap removed at operating temp.

Thanks

TNRabbit

I was losing a tiny bit of fluid directly from the water pumpt itself; however, since it was behind the timing belt shrouds, I couldn't see it. I only saw a little bit of fluid dripping on the pavement & never figured out exactly where it was coming from. When it finally failed, it blew out BAD and basically dropped everything within a couple of miles. It overheated WAY BAD and I thought I had toasted the heads, but since I replaced the WP it has run fine. That was about 5k miles ago.

Once the water starts flowing in the radiator it is going to flow out the top. Based on what you've posted thus far, I would let it run for a while keeping a close watch on the engine & overflow for signs of overheating. If you don't see anything and you don't get the "tink tink tink" sounds after your shut it down, I'd say your sending unit is the culprit.

I defer to someone else on your question about how to tell if the head gaskets are on backward; I've not experienced that before (Thank Goodnes!). But like I said before, if that was the case I would think you would have other problems.

When you were driving & thought is was overheating, did you notice sluggish performance or knocking? That's a telltale sign of overheating...

kdawghuntnfish

I never drove the truck when the temp gauge was up. I also have not noticed any other signs of overheating (besides the gauge). Hopefully it is the temp gauge. Thanks!

kdawghuntnfish

Well, I'm back from vacation and my troublesome 1990 rebuilt 3VZE in my 5 speed truck. I changed out my temp sender with another one of another 3.0. Not the problem. I decided to fully test the problem by driving the truck to look for more symtoms.

RESULTS: The truck is definatly running hot now that the air temp is in the upper 90's. I managed to hit the highway before the truck started to overheat and I noticed a HUGE lack of power (unable to hit 5th gear). As I was about 1 block away from the house, it started to push water out the overflow. Note: I do not have a fan shroud and waiting on a Tarus fan to do the electric fan mod. I realize the shroud is part of the overheating problem but do not believe it is the only culprit.

During the test run the check engine light also came on. It was actually two codes that came up. They were switch signals (ie. TPS contacts, neutral start and A/C) and open circuit in the knock sensor.

Code 5.1 ----- Switch codes
My question is could the idle be set too high or low causing the timing to be incorrectly set and thus causing the overheating problem? I really do not know how toucky the 3VZE engines are with the timing.

This code may also be coming up because the wiring harness is of an automatic truck were mine is a manual. I could have a terminal somewhere the would have to be jumped.

I do not have A/C.


Code 5.2 ------- Knock sensor
??????????? I need to still check on that, no clue.

By the way I am getting closer and closer to pulling the heads and checking the head gasket install. Did anyone install head gaskets that had any knowouts (perferated ports to knock out) over any water ports. I have seen these on other engines, but did not notice them on the head gaskets I installed.

kdawghuntnfish

Well,
Got my truck fixed and it does not overheat anymore. The cause of my overheating problems was the head gaskets. They were marked top, but not left or right. I put the repair off for a while because I was dreading the time, but all in all it actually went quicker than I thought. It also gave me a chance to do the Taurus fan mod which turned out very well. It took about 8-10 hours to do the head gaskts and the fan mod. Not including parts runs.

Thanks to all for your help.

Now on to my tranny problems- lost 1st gear.

mt_goat

Wow, so the HG was on backward huh. How much of the cooling ports get covered up when that happens? Thanks for the update.

kdawghuntnfish

I would estimate about 80% of the port was blocked. There was a hole in the gasket about the size of a pencil.

A BIG HINT to anyone checking for a backward head gasket would be to pull the bottom radiator hose at the thermostat and pull the thermostat. There should be a good rush or flow of coolant. The flow of the coolant that came out of my engine was quite a bit slower and only trickled from the HG restriction.

mt_goat

Good tip!

Epic Ed

Glad you found the cause. I'm just seeing this thread tonight, but 1/2 down the first page I was thinking the gaskets were installed backwards. It's a VERY common error to make for shade tree mechanics and even for those with experience -- my mechanic did it, too, and he owns a 2nd gen 4Runner!

Ed

MarkH

Kdawg, My heads are currently sitting on the floor of my shop after over two years of coolant flow problems. My truck did not have a thermostat in it when I bought it. Temps were ok in the summer but ran too cold in the winter. So I put a thermostat in and it overheated immediately. I was experiencing the same problems that you are having now. After several posts and threads I came to suspicion that I had a head gasket problem. That has proved to be the case. My 3.0 had two right side head gaskets in it blocking the main water inlet/outlet to the left head. I have read on this site that if the gaskets are on backwards they stick out in the back of the engine. Good luck,
Mark

mt_goat

How much do they stick out?

MarkH

I can't say. All I did was read it here. When I tried to check mine it was on the right side which was correctly installed. Left side was my problem.