Burping the coolant system - not getting hot enough

[mountainfarmer]

I just serviced my cooling system in my 1994 K1500.

I'm currently getting the air out of the system, the only problem is my truck fan is too effective.

Now that it took 2.5 gallons of coolant the engine won't rise above 165 at idle and thus won't actuate the 195 thermostat.

I believe the reason why is my fan is too effective.

Questions:
1. Any ideas on getting the truck to get hot short of just revving it? Or should I just call her good to go?

2. If the fan is so effective that it keeps the engine at 160. Should I swap from a 195 thermostat to a 160 thermostat to keep coolant flowing?

3. If I run a 195 thermostat with the truck operating at around 160, could the block get hotter while the radiator stays cool and thus produce engine wear?

 

[454cid]

If you just changed the thermostat, you may may have gotten a mis-boxed or bad part. I'm not sure if you've actually driven the truck yet. I'd suggest you do that first, and see if it warms up fully, and go from there.

 

[mountainfarmer]

If you just changed the thermostat, you may may have gotten a mis-boxed or bad part. I'm not sure if you've actually driven the truck yet. I'd suggest you do that first, and see if it warms up fully, and go from there.

I just did a twenty mile round trip test drive.

Before servicing the coolant system, when hill climbing, I could get near 205. Now it only gets to 175, which seems good to me. I think I am good with it as is. If I notice any strange engine activity over the next couple weeks I may replace the fan clutch to make sure it's the correct one.

My recollection is that the fan clutches are filled with a solid that turn into a liquid at a certain temp and that you can get different fan clutches that activate at different temps.

Could be the liquid in this particular fan clutch loosens up and spins around 160 is my thought.

In any event, she seems to be running happily which is good enough for me.

 

[termite]

I just did a twenty mile round trip test drive.

Before servicing the coolant system, when hill climbing, I could get near 205. Now it only gets to 175, which seems good to me. I think I am good with it as is. If I notice any strange engine activity over the next couple weeks I may replace the fan clutch to make sure it's the correct one.

My recollection is that the fan clutches are filled with a solid that turn into a liquid at a certain temp and that you can get different fan clutches that activate at different temps.

Could be the liquid in this particular fan clutch loosens up and spins around 160 is my thought.

In any event, she seems to be running happily which is good enough for me.

Sounds like either a failed open stat or the incorrect temp. Running that cool may result in excess condensation within the oil or possibly staying in open loop.

I'd pull that stat for another 195. Bonus points for testing it in a pot of water on the stove before reassembly.

 

[West 1]

The fan will not affect your thermostat. The stat is closed and coolant is not circulating till it opens. The fan cools the fluid in the radiator not in the engine. So two different issues. Check the temps at your thermostat housing with an IR gun and see what temp the thermostat is opening at/running hot at. Bad thermostats are out there for sale brand new so verify with the IR gun to make sure yours is working proper. Most open around 195* for this engine and you want that so the engine computer works properly.

For removing air from the system, Chevy small blocks purge air pretty easy but there are rules to follow. Raise the front of the truck slightly, 6" is enough to help air make its way forward. Put your Heater in the Full Hot position, heater fan can stay off but the heater core needs to be filled with coolant so open the heater control to full hot for the first 20 minutes or so or until you feel HOT air coming out the vents, not warm air but Hot air. Run the engine cap off letting air burp until you see the fluid circulating constantly inside the radiator. The upper hose will also be very warm to the touch at the radiator where the upper hose connects. If your truck has a dual heating system make sure the rear heat is turned to full hot also, again to purge air. Run them a while, it does not purge instantly. I usually run one at least a half hour after new fluid install to avoid air pockets.

The Fan clutch is filled with silicone, it is thicker when cold and can engage your fan, I think the factory says it should disengage on a cold start after 45 seconds run time. The silicone will settle to the bottom of the fan clutch when parked overnight, when this gets cold and thick it can cause the fan to engage when cold started. As it warm up the fluid pumps back into the storage reservoir. On many trucks you will hear the fan engage on cold start but disengage after you drive a block or less. Disengaged a fan clutch should spin your fan about 10-15% of engine speed, engaged it may be as high as 90% engine speed.

Edit: If you have an engine that keeps getting air in the system you have a Head Gasket Leaking, a small leak will put air in the system, a larger leak can cause fluid to blow out of the radiator cap. The radiator fluid can be tested to see if combustion gas is in the fluid to rule this out.

Mark

 

[Schurkey]

If you have an engine that keeps getting air in the system you have a Head Gasket Leaking,

Or a cracked casting.

 

[Caman96]

How are you getting a coolant temperature reading? Don’t go by the truck gauge.