Engine Temperature + thermostat issues (LOTS OF CONTENT) - VW Forum :: Volkswagen Forum
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post #1 of 97 (permalink) Old 09-23-2009, 09:50 PM Thread Starter
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Engine Temperature + thermostat issues (LOTS OF CONTENT)

So here is a cooling system and engine temperature issue thread. Read this before posting on your over heating car and such. I will also outline the commonly failing thermostat. So here's the issues:

Overheating:

-Check that your fans are cycling (If not check your fuse in position 19 for your radiator fans, check your thermoswitch is functioning on lower radiator, or check the fan motor itself)

-Check that you're not low on coolant and that the concentration is 50/50.

-Clogged coolant hoses or plugged radiator. If it only over heats at highway speeds sometimes the lower radiator hose collapses at highway speeds.

-Worst case scenario your head gasket could be blown.

-Thermostat is stuck closed

-Radiator fins could be full of bugs/ dirt etc; clean it out.

-Worn out water pump thus not being able to circulate coolant correctly.

Underheating:

-The only thing that will cause this is a thermostat stuck open, which i will go over right after this.

Thermostat symptoms and replacing (ABA Engine)

The thermostat tends to get stuck open on these 2L engines frequently and will cause the below symptoms. It will cause poor gas mileage and cause your engine oil to start sludging as well as lower than normal heater output. Mine was stuck open so i decided to change it. Its a tedious and dirty job if you're doing it by yourself with a jack on the garage floor. It took me 2 hours on my first time, with no breaks. So here's how it boils down:

Thermostat stuck open

-Will drop in temperature while driving at highway speeds and temperature will fluctuate.

-Will warm up SLOW, if it takes 10 minutes for your car to warm up on a hot day then its stuck open.

Stuck Closed

-Its simple your car will overheat since your thermostat is stuck closed and won't circulate coolant when it starts to over heat.

THERMOSTAT REPLACEMENT

First of all you will need the following for the job, i am not going into detail about belt removal. If you have only basic knowledge of working on cars, leave this job to the pros!(I am using tools in metric not imperial.):

-3L of coolant (VW pink G12 coolant) and 3L of water (Cooling system has a 5.8L capacity)
-Thermostat and O-ring
-Thermostat housing (Cheap part, tends to break and warp during removal)
-13mm wrench (For alternator tensioner)
-10mm socket (Thermostat housing), 13mm socket (All power steering bolts except 1), 16mm socket (Bolt that holds power steering pump to main bracket)
-22 mm socket for power steering pump tensioner cog.

1. Use your 13mm wrench to move tensioner away from you and let the serpentine belt hang.
2.Loosen all bolts holding power steering pump to the pivot bracket and use the cog to remove tension on the power steering belt. Don't try and turn the cog if all the bolts aren't loose or removed, you will strip the cog, it's soft metal. Then remove belt off the car, i left the serpentine belt just hanging on pulleys.
3. Now that belt is off, remove the 3 bolts that hold the power steering pump and bracket to the block. Once this is done the pump will drop and you can just let it hang, NO NEED TO DISCONNECT ANY POWER STEERING HOSES.
4. Open the expansion tank for coolant and get ready to drain it. Now that P/S pump is hanging, you will see the thermostat housing right about where P/S pump was. Now disconnect the coolant hose that is connected to thermostat housing and coolant will drain out of the system.
5. Use your 10mm socket to remove two bolts on thermostat housing (I used penetrating fluid to loosen these up, just in case). Pull the housing off and VOILA there is the thermostat, simply pull the thermostat right out. Might give you some trouble so use pliers if needed.
5. Put the new thermostat in, and O-ring on after the thermostat is in place (NOTE: The thermostat will not stay in place until you put thermostat housing back on. The O-ring is tough to keep in place with out it dropping out(Very frustrating), but keep trying it will happen.)
6. Now everything is the reverse of removal, good luck!

You will notice the difference in warming up time right away, its crazy

Power steering pump bolt info:

Last edited by mcrow; 12-31-2014 at 02:33 PM.
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post #2 of 97 (permalink) Old 09-23-2009, 10:33 PM
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nice sticky

Keepin it EURO

I <3 Euro Skanks

-94 jetta 2.0 x2-
-91 corrado G60-
-92 GTI-

1.8t swap in progress in the black mk3 :P
preparing for VR6 swap/build in mk2
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A performance rebuild for a k03 is about as effective as setting a brick on your dashboard.
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Does said brick have a ABD racing sticker on it? Then you just gained 5hp good sir!
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I'm doubting you have a "built" anything whether it's a car or a Lego Star Wars "X-Wing".
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post #3 of 97 (permalink) Old 09-23-2009, 11:28 PM
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question could this make your car shut off on you randomly?
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post #4 of 97 (permalink) Old 09-24-2009, 01:23 AM Thread Starter
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nope you got other problems.
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post #5 of 97 (permalink) Old 01-27-2010, 09:09 AM
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having similar problems, everythings new, all hoses heat up, fan switch also. but fans dont turn on, fuse good...whats my problem?
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post #6 of 97 (permalink) Old 03-03-2010, 04:16 PM
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For the warm and cold conditions is it a good idea to swap out the thermostat? like a high temp for winter and a low temp for summer?
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post #7 of 97 (permalink) Old 03-03-2010, 04:37 PM Thread Starter
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Nope not necessary at all. a 87 degree celcius one is just fine for all temperatures. Its the standard temperature one. I use it from -40C to +35C and no problems. Plus its a pain the ass to swap out each season.
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post #8 of 97 (permalink) Old 03-04-2010, 06:59 AM
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my temp needle stays all the way down unless im really getting on it or im in traffic going really slow what the problem?

vr6 dub
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post #9 of 97 (permalink) Old 03-04-2010, 02:31 PM Thread Starter
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engine coolant temperature sensor or bad thermostat.
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post #10 of 97 (permalink) Old 03-06-2010, 01:43 AM
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Nope not necessary at all. a 87 degree celcius one is just fine for all temperatures. Its the standard temperature one. I use it from -40C to +35C and no problems. Plus its a pain the ass to swap out each season.


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post #11 of 97 (permalink) Old 03-09-2010, 07:10 AM
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it a good idea to swap out the thermostat? like a high temp for winter and a low temp for summer?


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post #12 of 97 (permalink) Old 03-30-2010, 05:00 PM
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My car just overheated. luckily I was only 2 miles from the house when it happened. Popped the hood and smoke was everywhere. Antifreeze was bone dry. I waited for it to cool down and added the coolant. Started the engine with the hood open. After like 1 minute the coolant was squirting everywhere. It looked like it was coming from the side of the block (what I thought was the thermostat).

After reading this thread, I'm confused as to where the thermostat is?

Should I change it out? Is there a way of testing it? I need help ASAP because I cannot miss work tomorrow.

Thanks!!
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post #13 of 97 (permalink) Old 03-30-2010, 05:39 PM Thread Starter
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Thats not your thermostat, your thermostat is near the bottom of the engine. That is most likely your coolant flange that connects on the drivers side of the engine block. Wheres is squirting from?
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post #14 of 97 (permalink) Old 03-30-2010, 05:50 PM
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ok, I just saw your diagram in the other thread. It was squirting out right before the ECT sensor.....Could a bad sensor cause this??? I just called auto zone, they have both the sensor and thermostat in stock. Thing is, I don't think I can change the tstat. I don't have the tensioner cog....( I don't even know what that is).


quickly took a cell phone pic of where it was squirting out at......right where I disconnected the hose


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post #15 of 97 (permalink) Old 03-30-2010, 06:48 PM
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so the ECT sensor wouldn't cause the car to overheat right? It only reads the temp right? So, then its probably the tstat? What about the water pump?
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