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How-to: Replacing the thermostat housing (and hence how to R+R the thermostat!)

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[gti-vr6] Replaced my therm housing zappman@aol Mon, 30 Oct 2000 18:19:50 EST
Thermostat Housing Replacement "Scott U" <gr8scott95@hotmail> Fri, 07 Feb 2003 10:08:34 -0600
Re: [gti-vr6] Mk3 Overheating "Mike Fritz" <mike70@core> Mon, 7 Apr 2003 18:24:54 -0500
RE: [gti-vr6] Thermostat replacement "Mike Fritz" <mike70@core> Wed, 12 Nov 2003 22:52:16 -0500

From sentto-1455644-274-972948277-aqn=panix@returns.onelist Mon Oct 30 18:24:39 2000
From: zappman@aol
To: brett@kavi, jbowermo@yahoo
Subject: [gti-vr6] Replaced my therm housing
Date: Mon, 30 Oct 2000 18:19:50 EST
Cc: gti-vr6b@egroups
Well I finally got around to fixing my VR6's coolant leak today.  I found 
that the thermostat housing was slowly leaking the pink stuff.  With the help 
of Brett's copy of the library and the input of a few others (thanks Jeff) I 
decided I was going to fix it at home.  

I popped the hood and a cold one and looked at what I was getting myself 
into.  It looked easy enough; plenty of room to work under there.
[[ Here is a pic. aqn Wed May 7 10:00:31 CDT 2003 ]]

disconnected the sparkplug wires from the coil pack and used a 6mm allen 
wrench to remove the plug wire guide.  So far so good, next I pulled the four 
bolts from the coil pack itself and eased it over out of the way.  Now I was 
getting some where, I could easily see the thermo housing and the dried, 
flakey pink residue that was all over one side of it.  In order to gain 
complete access I removed one 10mm bolt from a wire mount and the three 
electrical connections on the housing were unplugged.  Then I removed the 
cheesy spring clips from the radiator hoses that were attached to the 
housing.  I quickly realized I had not drained the radiator fluid; hmmm no 
need to worry about it now; After hosing down the mess in the driveway and 
getting another cold one it was back to work.  I removed the three allen 
bolts that hold the housing to the block and pulled it out.  Over at the 
workbench I looked it over to see what the next step(s) would be.

It was obvious that the seal ring had failed because that is where the leak 
was the worst.  The connections between the two bolt on adapters were clean 
and dry.  I believe that replacing just the failed seal and putting it back 
together would have fixed the problem.  Instead I played it safe and bought a 
new housing and replaced all the o-rings and seals involved.  VW wanted me to 
replace the two adapters too, but then they wanted to charge me about $225.00 
to do it for (to) me, so I disregarded that advice.  I also put new real hose 
clamps on the hoses I had removed because I don't trust the spring clamps, 
especially after they have been taken off.

I assembled the new housing by removing the two adapters from the old and 
installing them on the new.  I removed the three electrical connections from 
the old housing and slid them in the new one.  As I said earlier all the 
seals were replaced with new ones and it was time to put it back together.

It went back together quicker and easier than it came apart.  I used blue 
loc-tite on all the bolts before they went in.  I did remember to fill the 
coolant tank and then it was time to test it.  It cranked right up and I let 
it idle for about two minutes then looked for leaks or low coolant in the 
reservoir.  Everything was fine so I went for a test ride.  Sure was nice to 
be in my car again, only one day of driving the truck was too much.

For the record the parts I bought were:

Thermostat housing  021 121 117 A     $44.40
Seal Ring           021 121 119 A       4.87
O-Ring              N 903 168 02        2.31    QTY 3
Seal                N 901 368 02        3.15
O-Ring              N 101 392 01        3.15
Gallon G12                             20.20 OUCH!
                            Total     $81.35

I spent about two hours total working, not counting the one trip to VW for 

I will be keeping an eye on it for the next few days.  If anything changes I 
will let you all know.


From: "Scott U" <gr8scott95@hotmail>
To: list@gti-vr6
Subject: Thermostat Housing Replacement
Date: Fri, 07 Feb 2003 10:08:34 -0600
I just finished putting the new thermostat and housing on my car
yesterday. I saw a few people that said they might be doing this soon
and wondered how hard it is. Let me just say that it looks harder to
do than it actually is. Once you get started it's not that hard.

The Thermostat housing is actually 3 parts and you can get them from for a total of $55.00.
The above pic is also here.

I also got a new thermostat while I was in there. It was suggested
that you get some screw-on type hose clamps to replace the squeeze-on
type that came from VW. I say amen to that.

The allen wrench size is 5 not 6 like it says in the library write up.

Start by taking the coil pack off. (now is a good time to epoxy it
if you haven't yet) Drain the coolant out of the car. I did this
by loosening the lower hose to the radiator. (Which if you replace
the hose with the screw on type it is very easy to take on and off
then.) Take the connector off the radiator fan and the 3 connectors
off the sensors on the housing. Then take off the 3 hoses that are
attached to the thermo housing.

Then there are three allen screws holding the housing to the
engine. Once the screws are out just pull the housing off in the same
direction that the screws came off. Piece of cake.

The housing that I took off was cracked and probably the cause of my leak.
The above pic is also here.

Everything went back together very easily. Put the new housing together
with the thermostat and the old sensors. Then screw the housing onto
the engine. Once that is done then hook the hoses back on the housing,
clamp them down, and hook up the connectors. Add antifreeze in your
flavor of choice. I used Prestone's Dexcool type antifreeze. It's about
half the price of VW's and it was made for an aluminum engine. Put
your coilpack back on and hook up the plug wires.

That's it. Crank it up and check for leaks. I've been running mine
hard for a couple of days now and have no leaks at all.  :)

Scott Ulrich
95 GTI VR6 - leak free edition

From: "Mike Fritz" <mike70@core>
To: "Joshua M. Ficksman" <josh@everbatim>, "GTI" <list@gti-vr6>
Subject: Re: [gti-vr6] Mk3 Overheating
Date: Mon, 7 Apr 2003 18:24:54 -0500
Lower hose is return, bad thermostat.  I replaced mine last winter by just
taking the thermo housing off, but it's a pain in the ass (one allen bolt is
totally blind).  I recommend just taking the whole coolant distribution
plastic housing off the head and then reinstall after putting the new
thermostat in.  180 degree thermostat is what you need.


----- Original Message -----
From: "Joshua M. Ficksman" &lt;&#106;osh&#64;everbatim<img src=/i/dn.gif border=0 width=35 height=15>&gt;
To: "GTI" &lt;&#108;ist&#64;gti-vr6<img src=/i/dn.gif border=0 width=35 height=15>&gt;
Sent: Monday, April 07, 2003 1:29 PM
Subject: [gti-vr6] Mk3 Overheating

Last Thursday on my way home from work, my car overheated after 10mins of
driving. Motor was cold when I started out. The upper hose from the radiator
is hot but the lower hose is cold as if there is no coolant running through
it. I don't know which is the return hose. I found that I can drive it if I
blast the heat and drive gently. It will barely overheat that way, needle
moves just a bit past the normal straight upright position. Common sense
says to start with the thermostat since it's the cheapest and least of all
evils. Can anybody think of anything else that might be wrong? The library
didn't have any clear instructions on how to change the thermostat just the
housing. Can someone give me the procedure? Some pics would be great if
anyone has any. I don't even know where the thing is. How much coolant I
will lose in the process, and what temp thermostat I should use. My car has
never run hot. Normally right around 210 to 212 (oil temp) Any help would be
GREAT!!! Thanks guys.

From: "Mike Fritz" <mike70@core>
To: <kconner@rahavindesigns>, "'Scott U'" <gr8scott95@hotmail>, "Gti-VR6. net (E-mail)" <list@gti-vr6>
Subject: RE: [gti-vr6] Thermostat replacement
Date: Wed, 12 Nov 2003 22:52:16 -0500
Yes, you are right, in retrospect, if you just take the "whole" housing 
off the head, it would be pretty easy.  But no, I like to do things the 
hard way, and I just took the thermostat "cover" piece off the main 
housing, you know, the one with the three blind allen bolts.  What kind 
of shithead engineer designs a thermostat housing cover that 
faces "down", and that you can't get to easily?  Similar to designing 
spark plugs where you have to drop the engine to get them out.  Oh 
wait, that was already done on the last generation Z28 Camaros!  
Anyways, my method took me forever but I finally got it.  I'm not 
bitter or anything.  ;D


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