Cooling question...

[SMOKEWAGON66]

Ok so ive searched several different ways and different keywords and havent had much luck so ill go ahead and ask.

Drove the truck this afternoon and drove it enough to get the engine good and warmed up, and when i got back i did some after operating checks and noticed that the top of the radiator was hot, warm in the middle, and ice cold at the bottom. I opened the draincock at the bottom and the coolant that came out was very cold....

in my best guesses, the fluid coming out at the bottom of the radiator should have been too hot to touch. So i squeezed the bottom hose and could hear fluid rushing through the radiator. It seems that the radiator is working but im wondering why its cold on the bottom. Which way does the water pump move the coolant? does it go top down or bottom up? Could the thermostat be stuck shut?


any ideas? Suggestions? i wanna drain the system and pull out the trhermostat, clean everything out and check the sending unit to see if it works..Any help would be greatly appreciated.

 

[glcaines]

I would first check to see that the lower radiator hose is not collapsing under suction. The coolant is sucked from the bottom of the radiator by the pump and expelled back into the upper part of the radiator if the thermostat is opened. If the lower hose is not collapsing, the next thing to check is the thermostat. I would go ahead and replace it if you have to remove it. However, you can also test it by removing it and placing it in a pot of water and heating it. You can see it opening and closing if it is functioning. Another possibility is that the thermostat is not closing at all and the coolant is never getting hot. A bad water pump is less of a likelihood, but the belt could also be slipping.

 

[Westech]

How long did you drive it? Sounds like the T stat just started to open when you stopped. IE: you did not drive it long enough. If it is not over heating and the gauge is stating 160-190 your fine.

 

[SMOKEWAGON66]

I would first check to see that the lower radiator hose is not collapsing under suction. The coolant is sucked from the bottom of the radiator by the pump and expelled back into the upper part of the radiator if the thermostat is opened. If the lower hose is not collapsing, the next thing to check is the thermostat. I would go ahead and replace it if you have to remove it. However, you can also test it by removing it and placing it in a pot of water and heating it. You can see it opening and closing if it is functioning. Another possibility is that the thermostat is not closing at all and the coolant is never getting hot. A bad water pump is less of a likelihood, but the belt could also be slipping.

The hose wasnt collapsed...although i didnt check it running. I planned on testing the T-stat today and if it didnt work i was going to leave it out until i can afford a new one, along with a new sending unit and mabe a couple new hoses. The top end ones have some weird colored corrosion around them, peeling the paint and discoloring the aluminum. Ive seen that before and its not a huge concern, but ill rectify it regardless. Ill report back once i get the T-stat and pump checked.

How long did you drive it? Sounds like the T stat just started to open when you stopped. IE: you did not drive it long enough. If it is not over heating and the gauge is stating 160-190 your fine.

I drove it across town, a good 10 miles one way. the gauge was floating between 160 and 190 however i dont know if the sending unit is functioning properly, and ive never been one to fully trust gauges on a older military truck...something i learned as a young private driving beat up 80's model AMG 9 series trucks. the top of the radiator wasnt so i hot i couldnt touch it for a second so i dont think it was really getting hot...its just that the coolant coming out the bottom of the radiator was just way to cold to seem right. I just wanna make sure everything is as it should be, because if this engine goes...im dead in the water for a long time.

 

[Heavysteven]

I overhauled my cooling system last winter. It was a chore, nothing complex just took labor. That would address any and all concerns about it. I had to replace mine due to rust at the bottom. Also, when I pulled mine out I went ahead and replaced the hoses, belts, and thermostat. It was easy with the radiator off and I am glad I did.

 

[Heath_h49008]

What's the thermostat's rated temp? If it's <190f it never opened... or if the bottom hose collapsed when it did open, nothing circulated. (You would have to check it running and hot, but most lower hoses have a rib or coil inside you can feel even when cold to prevent such collapsing from happening. )

If you have an IR/laser thermometer hit the water outlet when it's running hot and see where you're at. They're about $29 at HF...

It might not even be as hot as you think... but better safe than sorry.

 

[OldDominionIron]

Normal operating temperature is about 185F. Depending on the outside temperature, if you're not putting a load on the motor, you may not get coolant temps up to normal. Last winter I had to put a piece of cardboard with a 10" circle cut out of the middle to help increase temperature. The cooling systems on these trucks are incredibly efficient.

 

[nk14zp]

Normal operating temperature is about 185F. Depending on the outside temperature, if you're not putting a load on the motor, you may not get coolant temps up to normal. Last winter I had to put a piece of cardboard with a 10" circle cut out of the middle to help increase temperature. The cooling systems on these trucks are incredibly efficient.

I take my fan off in the winter. When you check/take out your thermostat make sure the bore it sits/rides in is smooth so it can slide easily , I have had to clean the bores up some before.

 

[SMOKEWAGON66]

Well, i drained the system, took out the T-stat and got as much crud out as i could. I checked the T-stat in a pot of boiling water, made sure it opens and then reinstalled it, refilled the system, and ran the truck at 1500 rpm with cardboard in front of the radiator and waited till the gauge got over 160. Everything seems to be working ok...the bottom of the radiator got warm this time, so maybe there was just crud in there and i got it out.... so one less worry!