I have had several cooling problems with this truck since I picked it up and most have been resolved. Long story short - cruddy, rusted radiator has been flushed, cleaned and blessed by a radiator shop. System has been back and forward flushed and a new 180* thermostat has been installed with a 50/50 mix. I still hear a couple bubbles in the heater core so it's not completely burped....

Ok... when idling it will run a steady 180* temp regardless of how long it idles - both with and without the A/C on and in park or neutral. If I put it in gear and roll around town, the temp creeps up to 190, 200 and eventually stalls out around 210*. Stop and go traffic accelerates this behavior but if I pull over and put it in park, the symptoms immediately disappear and the truck is idling back at 180*.

I also have an after market tranny cooler mounted in front of the condenser but I don't think this would cause a problem. This setup passes the "piece of paper" test...a couple pieces of paper are snugly sucked against the tranny cooler at idle and when in gear. It makes more sense that the problem would be greater at idle but come to think of it I haven't taken any tranny temps at idle and in gear.

Anyone seen this problem or have any suggestions? I'm thinking about relocating the tranny cooler below the condenser and radiator to see if that makes a difference.

 

well, on one hand - sitting at idle would move the least amount of air across the radiator - which would lead to higher temps. but it also puts the least amount of heat in the engine, as opposed to 2k rpms.

on the other hand, low speed idle creates very little heat in the transmission fluid, as compared to driving.

with normal driving, not climbing a mountain and towing a boat, the cooling system should handle AC, trans cooler, engine cooling without even trying hard.

i think your radiator might be about half stopped up.

 

i can't remember - was your fan clutch ok ? feels sort of sticky with some resistance. doesn't free wheel when engine is cut off ?

 

Not certain on the fan clutch. I got the engine up to operating temp, shut it off and spun the fan. It spun another 1/2 to 3/4 turn before coming to a stop. If this indicates the fan clutch is bad then I'll go get a new one. Not a fan of throwing parts at a problem if the part's not bad but autozone takes parts back.

The radiator shop scoped the radiator and it's clear. After 200 miles of driving the coolant is still green and clean - no brownish tinge or floating flakes in the overflow bottle.

 

fan clutch is good. when it spins for 15-20 more seconds its bad.

hhhmm...
when temp has climbed up to 210 or so, if you stop and grab ahold of the lower radiator hose, is it hot, lukewarm, or cold.

if you have an opportunity to run with no t-stat, see what happens.

 

The lower hose is 180 +/- 5* (according to infrared thermometer) at idle in park or neutral. Drive around a while and it's been as high as 200* with the same thermometer. I haven't read the trans cooler after driving but will tomorrow. My thinking is the air drawn across the trans cooler is maintaining a higher temp and preventing appropriate cooling....could be wrong but it's a start. Relocating the cooler may be the way I go.

The lower hose has never been cold or so hot you can't hold it. The upper is hot as it should be.

The heater core still seems to have air in it so the burping continues. Is there a bleeder valve somewhere for the heater core?

Running without a t-stat isn't an option now as I just filled it up.

I'll take some heat readings tomorrow and see where it takes me.

 

if you drain down about 2 qts into a clean bucket and strain it, you could remove t-stat with little loss. its a lot of trouble. the expected result is that it would run very cool, something like 150-ish on the gauge. if it didn't, that might tell us something unexpected.

lower hose should be running about 120-140. i think 180 is way over what it should be.

don't worry too much about the heater core, it'll eventually work itself out. no bleeder valve. if you park with the front end up a steep hill, and cap off, it speeds up the air purge.

i've got a trans cooler strapped to my condenser also, and it doesn't affect my cooling. temp gauge sits dead on 180 except when uphill and towing.

keep an open mind that the cooling passages in your radiator are stopped up, in spite of what the shop told you.

 

I took the temp readings close to the water pump inlet..... I'll recheck at the radiator outlet tomorrow and see if they're in the 120-140* range.

Worst case I put a new radiator in it. I'm not ruling out there's a clog somewhere or a coating inside preventing optimal heat transfer inside the radiator. I'm more concerned with the engine's water jackets and passageways.

 

looking through my little computer screen, i'm not seeing anything wrong with your motor its supposed to put heat in the coolant. i don't remember if you ran a compression check or not, but that would rule in or out an engine problem. water jackets and passageways are pretty big, and other than a little rust scale build up, there's not much to go wrong.

since the engine is supposed to put heat in the coolant, then in order to maintain 180 or 195 coming OUT of the engine, you have to be a lot cooler than that going INTO the engine.

the little cross passageways in the radiator might be stopped up. any way to test or clean or prove it is or isn't ??