New to forum and been searching/reading - LOTS of information but still not exactly sure which path to pursue first.

I just changed the thermostat and the coolant expansion tank on our '01 4.0 s-type. I read how important it was to properly bleed the air and have done this at least 1/2 dozen times (both through the cap above thermostat and through the heater line bleed).

However, cabin heater is not working (worked fine before these changes). Only clue I have is that during car warm-up (before thermostat is fully open), we get some amount of heat. Once car reaches running temp and thermostat opens - nada!

I'll keep reading but if anyone can point me in the right direction, I would be very appreciative!

 

If you're certain the coolant system was properly bled then check to see if the DCCV and CCM aren't toast. My first thoughts are that there is still an airlock existing somewhere or the new thermostat is remaining open.

 

Another clue. I've noticed that the auxilary fan is coming on when at idle after driving freeway speed. Doesnt stay on long but I dont recall this happening prior. Temp guage appears normal.

I too have been suspecting the new thermostat is sticking open but that conflicts with aux fan kicking on?

If I have air pockets, I have no idea how to get them out. I've bled at idle and 2k rpm. Pulled the thermostat cap and topped. Any other ideas on how to get remaining air?

 

Let's see if our Jag tech; Brutal comes to this thread. If not ya can sift through the forum archives using the "Search Forum" feature or send a private message to Brutal.

 

Did you definitely use the exact correct antifreeze?

Maybe your heater matrix is almost blocked.

Maybe one or more temp sensors died and the car thinks it needn't add heat.
Usual one that fails is the external one (front, behind where the licence plate would be / is).

Suppose you disable the engine cooling fan. Do you get cabin heat (set it on max of course)?
Ditto, but disable the a/c compressor.

 

I used Prestone GM DEX-COOL in roughly a 50/50 mix. Is this o.k?

I'll do a search on how to find, pull, and test sensor.

I'll do another search on disabling fan and compressor.

I'm determined to figure this out without putting it in the shop!

Bob

 

Don't think we have that over here! GM sounds worrying.