350 TBI cooling system problem

[fixmy59bug]

I think maybe my cooling system is too efficient.

First and foremost, the vehicle is an 89 GMC Suburban R1500. 350 TBI Completely stock engine and cooling system.

I was having a problem where the coolant temp would never even get to the first line (150*). My dad thought it was a thermostat problem (stuck open or non existant). So I buy a new 185* T-stat, gasket, and while I am there, the coolant temp sender. Replace all 3, do a coolant flush and proceed to burp the system. After (I am pretty sure) all the air is out of the system, I let it sit idle to check the temp. For the first time it gets up to full operating temperature. I take it out for a drive and the temperature drops like a damn rock.

My dad tells me it is possible the coolant system is too efficient. He ran into a problem like this before. He suggests I block off half the radiator to see if the temp is affected. So I block off the half that does not have the trans cooler in front of it. I take it for a nice 180 mile trip and the temp stays hovering right around 130*. The heater barely got warm enough to make a popsicle sweat.

When I got to my destination, I check everything else associated with the cooling system that I can think of. Fan Clutch was nice and tight, Water is curculating in the radiator so I assume the water pump is pretty good.

Is there anything else I should consider? Is there any way I can test the guage to ensure it is displaying the accurate reading?

 

[southernspeed]

If your heater isn't putting out heat AND the gauge is reading low I'd say you've still got a problem with the stat sticking open. Almost any other system problem will cause it to over heat. After a few miles even in sub zero temps you should be all toasty in the cab.
Check the stat again, you could just be unlucky and have had another bad one. Shouldn't it be a 195 in there? Not that that would make any difference to your heat really.

 

[Hogback Fabrication]

Thermostats are kinda known for being bad out of the box but...

Have you confirmed the heat of the motor with anything other than the stock gauge? Those are notorious for being inaccurate as well.

 

[jor]

Or could you have possibly put the thermostat in upside down?
jor

 

[dyeager535]

Agreed with first checking the engine temp with something else. If it's that cold, you should be able (carefully of course) to pop the radiator cap with little if any overflow after it's run for a long period. Shouldn't be much pressure built up.

If the engine temp is indeed low, somethings up with the thermostat. It is the ONLY thing that regulates engine temperature when dealing with a cold engine. With a proper thermostat, an engine can not overcool itself, period. A super efficient cooling system is a great thing, but it will still run at thermostat temp.

And please, when/if you do replace it, do yourself and the engine a favor and put the correct 195* in it, if indeed you did mean 185*. Seen 180*'s, but not 185*'s before.

 

[Jason4x4]

If your fan clutch was nice and tight at 130*, I would say it is stuck locked up and pulling too much air and cooling down too much, I would say replace the clutch.

 

[gone huntin]

I also found out the hard way not to use one of those "high flow" thermostats, the water flows through it too fast and it cools back down too quick. I agree with Jason that you need to check your fan clutch too see if it's locked up.

 

[Thunder]

I think you got a bad thermostat. Not uncommon these days with all the elcheapo parts out there. I cant see how a fan clutch stuck on can have any effect on the engine running too cool if the thermostat is operating correctly.
As dorian said the thermostat controls engine temp not the fan clutch. Also a 195 degree stat is the recomended one. 195 is where the ECM is programed to run.

 

[Slapperbar]

195* Motorad safety stat. and make sure the fan isn't locked up. The computer won't ever get out of cold start fuel dump below~ 190*ish.

 

[Redfrog]

try a new radiator cap with the proper psi rating.... ask me how i know