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350rs
03-01-2010, 02:55 PM
at startup ill have heat from my heater. then i wont once it gets to about 175. Then i will again once the thermostat opens. any ideas why that would be? I have a pic.. unsure of the name of the part thats outlined. Im wondering what its name is and if that tower has anything in it other than open-ness? Since thats directly associated with the heater thats my first thought since its heating and cooling normally.

350rs
03-01-2010, 09:51 PM
nobody knows the name of that part and weather or not it has something in the stack or whatever where to bleeder is?

zukiracer19
03-02-2010, 11:56 AM
prolly need thermostat, mine does that too and its constantly jumping around with heat, when heater works car is at normal heat, i'm just going to wait when i ship out my turbo to put a new one in

hahano404
03-02-2010, 12:17 PM
at startup ill have heat from my heater. then i wont once it gets to about 175. Then i will again once the thermostat opens. any ideas why that would be? I have a pic.. unsure of the name of the part thats outlined. Im wondering what its name is and if that tower has anything in it other than open-ness? Since thats directly associated with the heater thats my first thought since its heating and cooling normally.

that would just be called a water pipe. with a bleeder at the end. its to remove air in the system. crack it open till you get more than just bubbles.

pull hoses off the heater core and run a water hose to it and flush out any trash that maybe in it.

its either a bad pump, bad thermostat, air in the system or a clogged heater core.

3800SII
03-02-2010, 12:28 PM
at startup ill have heat from my heater. then i wont once it gets to about 175. Then i will again once the thermostat opens. any ideas why that would be? I have a pic.. unsure of the name of the part thats outlined. Im wondering what its name is and if that tower has anything in it other than open-ness? Since thats directly associated with the heater thats my first thought since its heating and cooling normally.

If your car is not overheating then your problem is 100% the bleeder valve on the
thermostat housing. You have a gi-normous air bubble in the system that circulates and causes a lack of pressure. Put the car back together and remove the radiator cap. Fill it full of fluid while the engine is running. once you see pressure build then replace the cap and unscrew the bleeder valve. it may take up to one minute before all the air is removed from the motor.
I work at Autozone part-time and every late model 3800/3400 that comes in on the lot for assistance with a similar problem this was always the cause.
BTW excessive air bubbles can cause you to warp a head, develop hotspots in the head, or simply blow the head gasket.

350rs
03-02-2010, 01:44 PM
just replaced both the water pump and thermostat. i wouldnt think it would be my heat since i sometimes have it and sometimes dont. more of a water situation. I have bled over and over again, but i suppose i could have missed some. It dosent make since to me.. but i can try again.

btw: not my car in the pic. just a pic of the part.

hahano404
03-02-2010, 02:02 PM
next time you do the bleed, run it open till you get a stream coming out of it to make sure all the air is out.

350rs
03-02-2010, 03:01 PM
i did another bleed. it was a stream the first, second, and now the third time. it keeps pullin air from somewhere. But i do NOT have a coolant leak. its been pressure tested. So i guess theres just a few high spots. ill bleed it for awhile and keep an eye on the temp.

hahano404
03-02-2010, 03:28 PM
if no air. than how sure are you on the installation of the thermostat (not backwards or an incorrect thermos)

other option is there is blockage in the core itself, keeping any air from beeing bled, or coolant to pass through.

350rs
03-02-2010, 04:08 PM
only one way the thermostat would fit. if put on backwards the water outlet wouldnt bolt on correctly. i tried it for my own satisfaction.

can not be a blockage in core. i still have heat. i just wont have it for 4 or 5 mins while its around the 175-200 degree mark.

im beginning to think its another faulty thermostat. or gunk in the coolant settleing on the thermostat and not letting it open at first. ill try a coolant system cleaner then flush again in a month or so as long as it dosent get worse.

cincydude
03-02-2010, 08:47 PM
I am having this same problem. I keep bleeding the air out, but it keeps coming back.

I have replaced the thermostat with a 180, the water pump, upper and lower hoses, overflow tank and cap, and changed the belt since I already had the water pump off.

I flushed out the coolant system getting a bunch of red dexcool sludgy buildup out. Replaced with the green stuff.

Once I bleed the air out it's good for about a day or two. Sometimes I get HUGE air pockets that take close to a half an hour of stopping and restarting the engine until I can finally get coolant to come out of the bleeder screw.

I'm stumped and help would be very much appreciated.

350rs
03-02-2010, 09:36 PM
oh yea im not getting that much air. its minimal. might not be bringing anything in at all. probably just burping still. its my only guess

hahano404
03-03-2010, 07:18 AM
if the rad wasnt replaced. it really shouldnt be much air.. def check if you have a good thermos. make sure to get from a reputable place like napa or an oe supplier.

does your hvac switch sound like it works? check connections on back of switch.

the blend doors may be stuck or the armature to the door is broke. have you been fiddeling around the dash lately?

3800SII
03-03-2010, 08:25 AM
I am having this same problem. I keep bleeding the air out, but it keeps coming back.

I have replaced the thermostat with a 180, the water pump, upper and lower hoses, overflow tank and cap, and changed the belt since I already had the water pump off.

I flushed out the coolant system getting a bunch of red dexcool sludgy buildup out. Replaced with the green stuff.

Once I bleed the air out it's good for about a day or two. Sometimes I get HUGE air pockets that take close to a half an hour of stopping and restarting the engine until I can finally get coolant to come out of the bleeder screw.

I'm stumped and help would be very much appreciated.

Here is an idea that can help determine if the air is getting into your system. Take the thermostat out, and fill the radiator fully as well as the overflow tank. Bleed the system while the engine runs. Once the fluid reaches at least 160 degrees, turn on the heat full blast and see if you still have the same problem. The water pressure should balance itself out rather quickly. If there is an air leak under the hood then you will see steam, fluid, etc.. If
you still have the same problem then it will be related to your HVAC controls.

cincydude
03-03-2010, 01:47 PM
Thanks for the input. Today I replaced the thermostat sensor and it seems to be working a lot better. I'll give it a few days and see how it holds up. I'll try to update in a few days.

Ajaxus
03-03-2010, 09:42 PM
This thread just saved my ass..my car started having the same problems last night and all day today, scared the bejeezus out of me when it started..then I remembered this thread, lol

I assume driving on it like this for one more day won't hurt it? Soonest I can get into the shop is Friday.

GA2000GTSpeed
03-03-2010, 11:55 PM
huh, learned something new... i probably need to bleed the air out of my system as well, another project to add to the list

350rs
03-04-2010, 06:41 PM
well its doing great now. If im moving it never gets over 200. even at a dead stop. it only made it to about 205 or so tops. That problem is solved.. NEXT!

and coincidentally it solved my high idle!! YAY!

Ajaxus
03-04-2010, 11:23 PM
hmm, well, we added some coolant to be safe today and the problem appears to have gone away..altho the coolant wasn't terribly low.

so my plan of action now, still swap the thermostats tomorrow (found a better deal from a friend..it's called "pay for the parts and give a case of beer for the labor...and then drink said beer while friend does all the work") one is new, one has 81k miles on it..the new one was already purchase so what the fock at this point. then check for any air in the system (which seems to be the culprit now). I think this is a great approach to making sure this doesn't happen again. lol

Ajaxus
03-05-2010, 02:12 PM
And 15hrs later an update..

We replaced the thermostat just to be safe..and because paying $6 to replace a part with 81k miles of wear/tear was something not worth passing up.

It does appear that the true culprit was an air bubble..which I think we got all of those out and she's running pretty strong now.

hahano404
03-05-2010, 02:24 PM
good to hear. maybe stuck behind thermostat, hard to tell. but anyways. if it comes back, shoot us an update

cherryred
12-01-2012, 07:37 PM
ok i have a 99 pontiac grandam se 3.4 we had to replace the thermostat bcuz the heat wasnt getting hot it was workin tho not that great tho and now since its been changed we keep having to bleed it like 4 times in the last 2 weeks when we bleed it we have really hot heat and car runs to 210 tops but as soon as its parked overnite from being bled the next morning we have no heat again then somedays we will have heat for awhile thenno heatif were driving highway then we get heat sometimes too then today it overheated twice on me no positevly wat is wrong with it but any input would help please