Overheating

[SSgt Andrews]

My 88K5 is overheating after replacing the radiator, water pump, thermostat and housing, and all hoses. It only overheats when the thernostat is in. When I remove it the heat is felt on both sides of the radiator and hoses. When it is in it only gets hot on the P/S of the radiator, the lower hose and heater core supply and return line and not the D/S tank or upper hose. I have put two thermostats in. The flow seems to be fine with the thermostat out but circulates through the heater core when the thermostat is in. I am about ready to set this piece on fire and calling it a day so some help would be muchly appreciated.

 

[4X4HIGH]

Are you installing the t-stat the correct way? The spring side goes down into the intake. Also it is sometimes hard to get all the air out of the system. If there is an air pocket trapped somewhere it will overheat everytime.

 

[SSgt Andrews]

Yeah i thought I put it in wrong the first time took it apart and it was right. As far as air I believe I got it all out.

 

[BoondocK5]

My 88K5 is overheating after replacing the radiator, water pump, thermostat and housing, and all hoses. It only overheats when the thernostat is in. When I remove it the heat is felt on both sides of the radiator and hoses. When it is in it only gets hot on the P/S of the radiator, the lower hose and heater core supply and return line and not the D/S tank or upper hose. I have put two thermostats in. The flow seems to be fine with the thermostat out but circulates through the heater core when the thermostat is in. I am about ready to set this piece on fire and calling it a day so some help would be muchly appreciated.

Well, you've done all the probable stuff, now it's time to consider the improbable.

Possible head gasket problem?

 

[70jimmy]

I would try a different thermostat in case you got a bum one.

 

[randy88k5]

Do you let the truck idle up to temp, or do you drive it around to get it up to temp and then notice these symptoms?

Is there a cooling fan on this truck? Is the fan clutch acting normal?

I second 70jimmy's suggestion. Test the thermostat in some boiling water and check operation. I've seen Stant's quality getting worse and worse (assuming that is what you are using)

Automatic or manual transmission?

 

[ChrisPerry]

My 88K5 is overheating after replacing the radiator, water pump, thermostat and housing, and all hoses. It only overheats when the thermostat is in. When I remove it the heat is felt on both sides of the radiator and hoses. When it is in it only gets hot on the P/S of the radiator, the lower hose and heater core supply and return line and not the D/S tank or upper hose. I have put two thermostats in. The flow seems to be fine with the thermostat out but circulates through the heater core when the thermostat is in. I am about ready to set this piece on fire and calling it a day so some help would be muchly appreciated.

This makes me think you might have installed the wrong rotation water pump. It would cause the lower hose to get hot but the upper would stay cold causing the thermostat not to work.

 

[Matt J.]

My 88K5 is overheating after replacing the radiator, water pump, thermostat and housing, and all hoses. It only overheats when the thernostat is in. When I remove it the heat is felt on both sides of the radiator and hoses. When it is in it only gets hot on the P/S of the radiator, the lower hose and heater core supply and return line and not the D/S tank or upper hose. I have put two thermostats in. The flow seems to be fine with the thermostat out but circulates through the heater core when the thermostat is in. I am about ready to set this piece on fire and calling it a day so some help would be muchly appreciated.

I'm not trying to hijack. I'm just curious as to what fixes your problem.

I'm having the exact same problem with my 88' (pick up). Mine always ran at 195*-200*. T-stat housing was corroded and the hoses didn't look that great. I changed the housing, t-stat and the hoses and now it wants to run at 230*-240*. Three t-stats later (all different brands) and it's still running hot.

Post up when you figure this out. I'm stumped. I did save the thermastat that was in there before I did the work. I just misplaced it somewhere in the garage. I have a feeling that I keep getting bad thermastats. I boiled all of them in water before installing and they all seemed to function properly. It's very frustrating when you do some preventive maint. and problems start to arise as a result.

 

[4X4HIGH]

You should stop by sometime and i'll help you look at it. I have an IR heat gun and we can closely check things out.

 

[Matt J.]

Edit: Double post. That was odd.

 

[Cornfield creations]

This makes me think you might have installed the wrong rotation water pump. It would cause the lower hose to get hot but the upper would stay cold causing the thermostat not to work.

Ditto, sounds like the wrong rotation. Should be hot on the upper hose, lower hose is the cold feed to the engine

 

[Matt J.]

You should stop by sometime and i'll help you look at it. I have an IR heat gun and we can closely check things out.

That would great if you could take a look Scott. You live so close that I could probably do 3 round trips between houses before my truck even gets to operating temp. Lol. I'll shoot you a pm. I've been meaning to talk to you about some possible side work on another project anyways. $$$

 

[SSgt Andrews]

Well I went out of town for a couple of days and the battery took a dump on me. Got it replaced tonight and will be taking the thermostat out tomorrow. The water pump is right, I double checked it. As far as head gasket it seems to be good. No fluids where they are not supposed to be and all compression is good. The first thermostat was 195 duralast from autozone, second was a 195 failsafe, now I have a 180 valucraft I think. Weather isn't helping much either. It's too cold out for it to sit and warm up.

 

[scrappyk5]

could be thermostat , you have changed it three times


could be a air pocket , put the t-stat in , take rad cap off with engine cold. and start it. shut it off once water comes out top of rad. let it cool top off rad , put cap back on and re-start. see what happens.

could be a blown head gasket , doubt it

could be wrong rotation pump , or even possible a defective pump.

 

[SSgt Andrews]

Alright I took one of the plugs out of the t-stat housing and pushed the t-stat down with a screwdriver, no air came out. it was a failsafe t-stat so it locked open now coolant flows freely. I bought a 180 t-stat and will put that in today, it seems to work freely. I can move the valve with my fingers the other two I could not. So we will see and I'll let yall know. Thanks for all the input.