kdawghuntnfish

Anyone ever have a new thermostat that was bad. I posted a thread https://www.yotatech.com/forums/f116/fan-shroud-running-warm-88477/ with an overheating problem and upon further investigation I noticed that the top radiator hose was getting warm, but not the bottom when the engine was at operating temp. Also, only the very top of the radiator is warm when the engine is at operating temperature. There was a new thermostat installed when the engine was recently rebuilt. The radiator looks pretty clean inside, but I have not ruled that out that it may still be plugged. The water pump was repalced during the rebuild, and seems like it is trying to work because there is pressure and warm water at the heater hose on the firewall.

ovrrdrive

Sure the new thermostat isn't in backwards?

You could probably check for a blocked radiator by pulling the bottom hose with the engine off.

midiwall

Yes, I've gotten a bad thermostat - twice actually. Once was the wrong temp in the right box, the other time the thermo didn't have the bleeder hole (bypass hole?) in the flange.


You've got a 3.0, right? If the coolant flow is the same as on "our" engines (the 3.4L) then the bottom is IN, the top is OUT. So the bottom should be hotter than the top. If it's not (as you says yours ain't) then you ain't got no flow - that's bad.

kdawghuntnfish

I just pulled the thermostat and it was in correctly. It was a 180 degree F thermostat. Radiator is not plugged by the rate the antifreeze came running out. Any other ideas? Thanks

reggie 00

Double check install, and make sure you purge before you cap the radiator.
To check the thermistat toss it in boiling water to see it open, just make sure its above the rating of the stat, use kitchen thermometer to check actual temp.

^VooDoo^

Midi, Thats backwards....
The top hose should be hotter.
As with all radiators the bottom should be cooler since the fluid is cooled before it reaches the bottom and returns to the engine.
If it was the otherway and you were only a hair low on coolant your engine would cavitate air and overheat.

ELD

kdawghuntnfish,I don't want to scare you but this sounds like the same problem I had with my truck.

When I bought it I was told they just replaced the head gaskets. Guess what they did, they installed them backwards. Someone didn't know what was the right side or the left side of the engine.

After installing new head gaskets the correct way my overheating problem went away.

Hope this isn't your case but it took alot of head scratching to figure mine out.

Good luck!!!

ZUK

iTrader: (1)

I don't know if I would give the radiator a good bill of health based on that kind of flow test. If you let the vehicle reach thermal stabilization (about 20 minutes running time) and the top is warm/bottom cool then that's a radiator issue. I had it happen....it did cost me a blown head gasket on my 22RE.

Try this test.....remove the cap and let the engine idle and warm up. This may take 15 minutes. Keep an eye on the temp gauge and watch the fluid flow in the rad cap opening.

For the first 5 or 10 minutes , you will see very little flow.....an occasional flow then it stops.....and finally a solid consistent flow as it reaches thermal equilibrium.


Observe the flow....note the color...is it brown ?......when you give it some throttle does it overflow out the cap?

midiwall

Right, but that would be in a situation where the inlet is on the top of the radiator, right? Isn't the inlet on these engines on the bottom? I was told that once, it didn't seem right, but I just accepted it.

I can't find anything in the FSM that talks about which is in vs. out.

mt_goat

Yeah that's right, into the engine through the bottom hose. Out of the engine through the top hose. Into the radiator (hot) through the top hose, out of the radiator (cooled) through the bottom hose. So top of the radiator should be hotter than the bottom.

kdawghuntnfish

If the head gaskets were installed backward wouldn't they be sticking out the back side of the motor on one side and out the front side on the other? I double checked them before the heads were installed and they we installed correctly. Thanks

midiwall

Whoops... I brainfarted and got it right, though it was backwards from what I was once told.

I meant inlet to the radiator.

Okay... brain fart subsiding now... and... memory replaced with correct coolant flow.


CARRY ON! (thanks guys)

mt_goat

IIRC, there is an incorrect way of putting the HG on that looks right at first glance except if you look closer you see it blocks the coolant flow in one or more passages. Never done a HG myself but I've read about this problem.

kdawghuntnfish

Well, thermostat checked good, so I reinstalled it. I decided to test the radiator according to ZUK. I started the truck and let it warm up and as soon as the truck reached normal operating temp I checked flow at the radiator cap. At operating temp, I don't even need to throttle the engine to get a good amount of water to come overflow out of the cap. The temperature of the radiator was still hot at the top and cool at the bottom. This is what I expected since I did not find or repair any problems. The color of the antifreeze was fine. Think the radiator is plugged even though it is looks clean?

I should not probably be second guessing myself, but I am going to ask a question on the head gasket theory because I installed them so long ago. If I am getting flow out the top of the engine doesn't this diprove the head gaskets are installed wrong and blocking passages?

ZUK

iTrader: (1)

New radiator if you let it idle long enough and the bottom still was not up to temp.

Slowrunner

I have the same problem , the top hose gets really hot and bottom just warm almost cold. My truck does not over heat although. Just came back from Saskatoon(3500km trip)with no over-heating issues at all. I replaced my thermostat and anti-freeze before I left. I believe my rad has a partial blockage which is causing the hugh difference in temperatures.

kdawghuntnfish

Slowrunner, What is your temp running at? My temp is not actually overheating either, but it is darn close. The warmest it gets is about 1 needle width before the red. When I turn the heater on it brings the temp down a couple of needle widths from that. I don't let the temp stay up that high except for testing for bad parts. By examining past posts I want to get this fixed before I destroy my head gaskets.

^VooDoo^

Using the heater is like adding more Radiator surface and airflow, Did you get that shroud on?

kdawghuntnfish

I just checked the radiator and it seems ok. I removed the radiator and stuck a garden hose into it. I plugged the bottom hose pipe off the radiator and filled the radiator. When I released the water it ran out in a couple seconds with the garden hose still flowing water. Not plugged.

I still haven't installed a shroud, but that should not affect the water flow problem I am having. The fan pulls good through the radiator without the shroud. It will hold a 1/4" piece of plywood 1' X 1' up against the radiator.

I noticed my heater hose coming out the top of the motor will heat up before the radiator hose whick comes out the same location. Air in the system. I don't think the radiator cap is releasing pressure and is trapping air in the system.

I am going to try a new radiator cap, before I check the H2O pump. I didn't install a new pump when I rebuilt the motor as proviously stated.

Any one know if there is a way to check the head gasket install w/o pulling the heads?

mt_goat

Well if the radiator is not plugged then my guess is the T-stat is not opening, maybe there is trapped air around the T-stat keeping it from getting hot enough to open. Did you install the jiggle valve at the top or bottom?