# Plastic thermostat housing leak leak leak, getting old



## oilpangasket (Dec 5, 2007)

So a few months ago I noticed my thermostat housing was slowly leaking water on my garage floor. I could squeeze the lower hose and the water would just squirt out. Plastic housing was warped. I replaced it and all the O-Rings. I jacked my car up the other day a few months after I changed everything to take off my oilpan to weld on a 1/2" pipe thread bung and make my downpipe and guess what was on the garage floor.... AGAIN?
Starting to get really old really fast. Never seen a 2L do this so many times. Is there a good fix other than keep changing the housings? JB welding the damn thing comes to mind. This is gonna set my project back because now I have to order another t-stat housing.




















_Modified by oilpangasket at 5:39 AM 2-15-2009_


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## twicepardoned (May 2, 2006)

must be the head then??? try using copper silicone gasket stuff.


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## Jettaboy1884 (Jan 20, 2004)

*Re: (twicepardoned)*

Try to source an old metal housing. As long as it's not cracked or damaged, it should seal up flush. 
I always pull them from junkyard cars whenever I find them. http://****************.com/smile/emthup.gif


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## mrdub27 (Mar 25, 2002)

*Re: (Jettaboy1884)*

have you checked your water pump.. on the bottom of the housing by the puley there is a breather.. this breather leaks when the internal seal goes.. meaning the water pump is TOAST..







the drip in your pick is a common sign of the water pump seal gone bad..







Noticed any reduced heat in the car .?? or high coolant temps..?


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## spitpilot (Feb 14, 2000)

*Re: (mrdub27)*

The "polymer" (aka plastic) flanges VW switched to for cooliing input and output on the engine are poor parts..engine heat degrades the material...they are more prone to install issues than metal parts etc....all to save a few cents I'm sure. Anyway..after replacing a couple of coolant flanges on my MKIII...two tips..#1..apply some silicone grease or at least dishwashing liquid soap to the oring so it can "squirm around" and make a good even seal while your tightening the mounting bolts. #2 Tighten those bolts a little at at time sequentually..DO NOT just crank down on one (unless you enjoy chagnin these flanges often..since crankin down on just one bolt risks crackin/warpin your new flange)..and don't overtighten the mounting bolts..the head flange bolts are only supposed to be torqued to 80 inch pounds...







...and I 'd bet the thermo flange bolts carry the same spec! Cinchin up way tight on these will also risk crackin/warpin ne part!


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## oilpangasket (Dec 5, 2007)

*Re: (spitpilot)*

The temps are all normal and the water pump was new when the motor was rebuilt. I know its leaking around the Plastic thermostat cover. I think Im just gonna load up the new one with silicone and torque it down right and hope for the best. A metal therm cover would be awesome to have.


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## fixmy59bug (Apr 9, 2002)

*FV-QR*

Out of curiosity, why are you running green coolant?
Isn't the pink stuff specially formulated for the different metals (aluminum head and cast iron block) where as the green stuff is not?


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## Jettaboy1884 (Jan 20, 2004)

*Re: FV-QR (fixmy59bug)*


_Quote, originally posted by *fixmy59bug* »_Out of curiosity, why are you running green coolant?
Isn't the pink stuff specially formulated for the different metals (aluminum head and cast iron block) where as the green stuff is not?

That's a good question that I am wondering myself.
People always say that the VW pink stuff is for our aluminum heads/iron blocks, but it's not like there aren't hundreds of other models of cars on the road with this exact same combination. (and of course there are some that are iron/iron, and aluminum/aluminum...)


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## fixmy59bug (Apr 9, 2002)

*Re: FV-QR (Jettaboy1884)*

True. And each manufacturer that has a different materials also has a special coolant. Gm has Dex-cool for example.


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## oilpangasket (Dec 5, 2007)

*Re: FV-QR (fixmy59bug)*

I used to run the pink crap a long time ago but it got old paying so much for it and the closest dealer is too far away so I just started using prestone and evaporated water. Never had a problem with it.
GM Dex Cool coolant actually does more harm than good. After so many miles it starts to turn into what looks like coffee grinds, and it cant be mixed with green. All the GM people I know just use green coolant instead.


_Modified by oilpangasket at 6:55 PM 2-15-2009_


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## WindsorJetta8v (Mar 13, 2001)

*Re: FV-QR (oilpangasket)*

you said you just changed the gaskets, try chnging the kousing the plastic could be warped or something


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## spitpilot (Feb 14, 2000)

*Re: FV-QR (WindsorJetta8v)*

VW has published tech infor for years saying that any coolant must be "silicate/phosphate free"...there was a tag on my 16V Rocco coolant fill cap with those exact words...if you check coolant labels, the "long life stuf" says meets those requirements..the cheapo stuff you see for $5/gallon doesn't! Just don't mix coolants! Flush good, then refill...don't overconcentrate either that can cause precipation/cloggin of system too! http://****************.com/smile/emthup.gif


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## germancarnut51 (Mar 23, 2008)

*Re: FV-QR (oilpangasket)*

From owning an A2 Jetta, I know that the plastic housing don't last forever, and since they are fairly cheap ($5), I keep new spares at home, and replace every time I do the waterpump and/or thermostat.
For the MKIII, I am planning on keeping the cylinder head coolant flange, the thermostat cover, and the thermostat cover adapter/extension at the very least. I get mine from europartsdirect.com or stopshopanddrive.com. Free shipping on Orders over $50, so I have a running Wanted List of stuff (gaskets, seals, o-rings, sensors, belts, hoses, etc) that I need or want to keep for spares (have you been to a VW and seen what the little stuff costs?). When my list gets to $50, I place an order, or if something on the car breaks and I need to order immediately, I place an order for the emergency replacement part, and add enough parts from my Wanted List to get the order over $50 and get the free shipping. Shipping normally costs $8-$10, so doing this is like buying $50 worth of stuff for $40 (20% discount). And the prices from these two Internet Companies are usually great to begin with.


_Modified by germancarnut51 at 10:28 AM 2-16-2009_


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## oilpangasket (Dec 5, 2007)

*Re: Plastic thermostat housing leak leak leak, getting old (oilpangasket)*

Finally got to it. Turned out the upper water pump hose clamp came lose. Took awhile to trace down the leak.


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