hey guys i have a 1990 dodge ram 250 diesel pickup, the HUGE problem im havin is it keeps trying to heatup, what i have done to the truck in about the last year is new head gasket, new water pump, new top and bottom rad. hoses, 3 new thermostats an rad. caps the last of both came from cummins, it was doin fine until i replaced the 2 rad. hoses an flushed the coolant system i put all new coolant. now it tries to heat up an i bleed the plug on top of the thermo. an lot of air comes out but it never helps, any ideas what could be doin this

 

Kind of sounds like there is still air in the system.

Does the truck get hot itself or is it just the gauges that show the truck as getting hot?

 

If all the work was done to spec, I'd say your head is junk. I'm going through that right now....

 

A combustion gas tester will check for exhaust gasses in coolant. A damaged head is high on list. Don't forget what a "plugged rad" will do. You did say problem started after flushed coolant. Plugged tubes after flushing sounds possible and would explain.

 

to answer your question DrewGzy i think air is still in it myself but i cant fiqure out how to get it out an the gauge in side it it has the cold and hot marks and 4 marks in between, once it starts warming up it goes from the cold mark past the 1st mark of the four in the middle then past the second an from what i understand when it gets in between the 2nd an 3rd mark it supposed to drop bac but it keeps goin towards 3rd mark, then i have to get out an either let air out of the rad. cap or the plug above the thermo. an then it drops bac in between the 1st an 2nd mark an fluwates on an both sides of the 2nd mark. an during the time u drive it, it might doin the same again an might not.!!! an to G1625S im pretty sure all the work was done right an i feel for ya its bad wen u cant drive it an cant fiqure out whats goin on, did u do any work to it b4 or did it just start happen

 

dozer12216 thats the only test i havent done yet, an thats all i did was flushed it an put new hoses, What are the peices that you are sayin could be plugged and causing it

 

also when the gauge goes towards the third mark or towards over heating i lose all heat an the air goes ice cold but when the gauge goes bac to the 2nd mark i have hot heat, hope this helps in someone giving me more info

 

Sounds like you definitely have air in the system still. Keep tryin to get the air out dude you'll get it.

 

Radiator core plugged was my thought.
To get air out. Raise front end as high as practical. Run and warm engine with cap off (careful) and heater on. It should purge itself. Let it cool, refill, and repeat with cap on.
Engine is generally not difficult to purge. The repeating of still getting air is a worry.
If it blows coolant, see earlier statement.

 

Are you positive that your not putting the thermostat in backwards?

 

yea it was put in right

 

The repair manual says on the second gens; to only fill with the engine shut off!
I have heard also on 1st gens; to raise the front end up while filling!

Farmer Tom

 

yea ive done that, i boiled water up to 180 and put two of the same thermostats in the water to see if they would open an they did so mayb more ideas