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View Full Version : Thermostat stuck open?? I already have it out.. (no heat, takes long time to warm up)



Supermario680
01-19-2015, 12:49 PM
98 2.8 30v. takes a long time for the engine to warm up in summer. In winter, when its below zero, the needle doesn't even crack "C" at all unless you've been driving for like 45 mins. I assumed the thermostat was stuck open so I ripped it all apart....

but it doesn't appear to be stuck open... seems to open around 160 ish and close a little lower.... Seems a little low in my opinion but i think i would have at least SOME heat if it was 160 deg....

but its so bad that the INSIDE of the windshield is frozen so bad I can't chip it off, which means I can't see out the window at all... which is a big problem...

I currently have the timing belt off, and thermostat out and have a new thermostat in hand... but wondering if there's anything else I should check while i have it all apart...

Other ideas are cogged heater core of course... but engine appears to be too cool too (unless sensor is messed up too), and heat works OK once finally warm, never super hot though I don't think........

bhusted
01-19-2015, 01:04 PM
A clogged heater core is not unheard of for these cars....

After the engine had run for some time but indicated "cold", did you ever pop the hood to feel the radiator hoses? Is the thermostat you took out OEM or aftermarket? How about the replacement you bought? I've never had good luck with aftermarket thermostats and would recommend only using OEM. It's also possible that while the one you removed was working, it was installed backwards, which I think would hold it open all of the time. Do you remember the orientation when you removed it?

Avant Nate
01-19-2015, 01:22 PM
A clogged heater core is not unheard of for these cars....

After the engine had run for some time but indicated "cold", did you ever pop the hood to feel the radiator hoses? Is the thermostat you took out OEM or aftermarket? How about the replacement you bought? I've never had good luck with aftermarket thermostats and would recommend only using OEM. It's also possible that while the one you removed was working, it was installed backwards, which I think would hold it open all of the time. Do you remember the orientation when you removed it?
I also had bad luck with a Stant thermostat, OEM solved the problem.

Supermario680
01-19-2015, 01:25 PM
A clogged heater core is not unheard of for these cars....

After the engine had run for some time but indicated "cold", did you ever pop the hood to feel the radiator hoses? Is the thermostat you took out OEM or aftermarket? How about the replacement you bought? I've never had good luck with aftermarket thermostats and would recommend only using OEM. It's also possible that while the one you removed was working, it was installed backwards, which I think would hold it open all of the time. Do you remember the orientation when you removed it?

no never got around to checking the hoses unfortunately lol. Looks like an OEM audi I believe. don't think its possible to install backwards and looked correct to me, not sure if it would bypass anyways.

frozenpuppy
01-19-2015, 03:14 PM
98 2.8 30v. takes a long time for the engine to warm up in summer. In winter, when its below zero, the needle doesn't even crack "C" at all unless you've been driving for like 45 mins. I assumed the thermostat was stuck open so I ripped it all apart....

but it doesn't appear to be stuck open... seems to open around 160 ish and close a little lower.... Seems a little low in my opinion but i think i would have at least SOME heat if it was 160 deg....

but its so bad that the INSIDE of the windshield is frozen so bad I can't chip it off, which means I can't see out the window at all... which is a big problem...

I currently have the timing belt off, and thermostat out and have a new thermostat in hand... but wondering if there's anything else I should check while i have it all apart...

Other ideas are cogged heater core of course... but engine appears to be too cool too (unless sensor is messed up too), and heat works OK once finally warm, never super hot though I don't think........

Put the thermostat in and youll be fine. Drove around with the same problem for two winters and finally did a timing belt job on my car. It fixed the problem. The only other thing that can cause this is an air pocket creating inconsistant coolant flow and your car would over heat or a plugged heater core.

Don't worry, if you want to check your heater core the Inlet and Outlet hoses are located right next to your battery and are covered in vacuum cleaner type plastic. Pull both of them off and rig up a couple coolant hoses to a blower gun. fill coolant in the hose and hold it upright, insert blower gun *(doesnt need to be a tight fit) and blowthe coolant out the other side.

** just remember to be gentle with the compressed air to some degree, although unlikely you dont want to over pressurize your heater core and potentially crack it.

You might surprise yourself. Although i can almost promise you your core isnt plugged, I have actually blown out some interesting debris from any core ive done this with and is a good preventitive measure.

Hope all is well. Good luck

Supermario680
01-20-2015, 12:59 AM
Thanks, I came up with the idea to heat both of them on the stove together and compare using a laser pointer to see the cracks. The old one started opening around 160-170 where the new one stayed closed until after 200. By 200 the old one was wide open where the new one was just starting to crack so that appears to confirm my theory about it being stuck open (more like weak spring) and makes me feel much better about putting it all back together! Thanks!

TheAussie
01-23-2015, 04:42 PM
I have this same problem. Planning to buy THIS (http://www.ecstuning.com/Audi-B5_A4-Quattro-1.8T/Engine/Cooling/Refresh_Kit/ES2608143/) from ECS to re-do the whole cooling system. overkill?

How hard is the thermostat to get-to?

Supermario680
01-23-2015, 04:58 PM
I'm not sure where it is On a 1.8 but on the 2.8 it was behind the timing belt.... so it was a huge pain in the ass

Supermario680
01-23-2015, 05:19 PM
I forgot to mention that I STILL did not have heat but at least now my car made it to operating temp eventually. Stayed C then sudden to rise to the middle.

I found that the heater core hoses were still cold so I cracked open the hose with the bleeder hole and air squeaked out, I opened it with the car running until coolant started trickling out then reconnected it. My car swallowed a bunch more coolant and then the heat started working slowly

smittyzz
01-23-2015, 06:26 PM
I forgot to mention that I STILL did not have heat but at least now my car made it to operating temp eventually. Stayed C then sudden to rise to the middle.

I found that the heater core hoses were still cold so I cracked open the hose with the bleeder hole and air squeaked out, I opened it with the car running until coolant started trickling out then reconnected it. My car swallowed a bunch more coolant and then the heat started working slowly

Sounds like its air, you need a serious burping..
Take the overflow cap off when cold and let it idle like 5 to get stuff cycling. Hold rims around 1500 to 2k and it will hopefully start bubbling or burping also blip the gas. Once it's a steady flow in the overflow and the cars up to Temp rescrew the overflow cap on, hold at around 1500k again, it should start sucking the coolant down, once it stops or your coolant is gone shut the car off and COMPLETELY COOL!
Repeat till heat arrives

Supermario680
01-28-2015, 08:46 AM
Okay thanks I will have to try it.

TheAussie
01-31-2015, 06:37 PM
So here's a little update on whats going on with my car...

Cranked her over yesterday after sitting for a little while. She started up fine like i expected and then the oil light came on and started beeping and flashing. so i turned it off and tried again, same thing.

Looked at the coolant level and it looked pretty close to empty.

Also like i mentioned before, previously when i've been driving it the temp has stayed really low and when coasting down a big hill the temp will sometimes drop untill that same light comes on and flashes. i turn it off and try again and usually it goes away.

Anyone have any suggestions?

Supermario680
01-31-2015, 06:43 PM
Well there is a coolant level sensor... You sure that's not what the warning was? If you want to see it again just unplug the sensor under the reservoir. And check the oil level obviously too...