skpyle

Hello Gentlemen,

Very soon, I will be reinstalling the water bridge and thermostat housing on the Red Witch. I understand that sealing is done with O-rings. A large black one for the water bridge to block, slightly smaller black one for the thermostat housing, and two smaller red ones for the water bridge to the cylinder heads.

However, I found black sealant on the water bridge O-rings. This dates back almost 20 years. I have cleaned all the mounting surfaces and removed all the sealant. I have new O-ring seals for everything.

Should I add supplementary sealant?


Another question: The areas where hoses connect to the water bridge and thermostat housing were never powder coated. They had some corrosion on them when I pulled the hoses off. I have scrubbed off the corrosion with a scotchbrite pad. What can I put on the areas where the hoses go to keep this corrosion at bay?
Dow 111?
Antiseize?
Other?

Note, I am not replacing the inner seal in the water bridge for the thermostat. I was replaced less than a year ago, and looks fine.





Black sealant on O-ring.






Sealant on mounting O-ring.











Corrosion on thermostat housing water outlet.






Corrosion on water outlets on water bridge.






Cleaned water outlet on thermostat housing.






Cleaned O-ring mounting area on water bridge.






Cleaned water outlets on water bridge.






Cleaned O-ring mounting area on water bridge.



Thanks for any and all advice!

StratfordShark

When I installed new o-ring and gaskets on my last S4 I didn't use any sealant, just wetted gaskets with coolant. No leaks.

The Forgotten On

I only used sealant on the thermostat housing that the lower radiator hose attaches to due to a PO damaging it.

Otherwise you don't need to use sealant. Just make sure all o rings and gaskets are fresh and quality.

buccicone

I put some silicone grease on the O-rings. Slides in nicely without distortion. Please correct me if I am wrong.

Adk46

If I recall correctly, my powder coating guy filled my hose-connection corrosion pits with some standard high-temperature epoxy, and then carried on with the coating.

Chris Lockhart

Seth, I have some special Alodine 57 wipes that prep the magnesium/aluminum alloy for paint. (I can give you one to keep. One will do a large area.) I would clean the corrosion completely with a wire brush, apply the alodine then coat with some Rustoleum paint in the silver color of your choice. The metal needs to have some protective barrier or it will continue to do the same.

Mrmerlin

I would take that WB and have it bead blasted to remove all the powder coating,
this will also remove the corrosion.
Use DC111 on the black O rings and on the red gaskets.
The DC 111 will keep the O rings soft and thus they will not leak from age

NOTE if your using the the gaskets for sealing to the head,
a lite coat RTV blue or red on the connections to the head .

NOTE the powder coating may look nice, but it causes functional issues when its installed,
usually a poor ground connection,
this then causes the temp sensors to give false signals.
If you must have the PC ,
then make sure the bolt holes and the temp sensor holes and mounting surfaces are clear of any coating,
so a positive ground path can be established.

I would suggest to replace the anchor bolts for the WB. use anti seize on the threads

NOTE the rear thermostat seal looks like its failing, it should look smooth,
I would replace it,
its easy to remove now.
dont put any DC111 on the hose connections or the hose will slide off the port.

NOTE inspect the hoses for internal damage from the little nipple and the top hose from the metal ring,
these will abrade the hose and cause the leak to come from the end out the threads.

NOTE usually with original hoses its best to replace all three that go to the WB

SeanR

I agree with Stan but use the VR Reinzosil on the paper gaskets where the bridge meets the head.

skpyle

I'll respond to everyone shortly, but first I have a question:

Should I be using the red O-rings AND paper gaskets to seal the water bridge to the heads?

Bertrand Daoust

This is what I did and would do it again.

It was leaking before (no paper gasket). Not anymore.

SeanR

I do.

davek9

Also after mounting the Water bridge, a good check is Ohm out the threaded Sensor holes to engine Ground, should be Zero Ohms.
I do this on Non-Powder coated ones too.

Dave K

skpyle

Excellent, good to know. Thanks!




I understand, thanks! All gaskets and seals that I have purchased are from Porsche. So, I think I am good there.




Mike, that is what I am leaning towards. I have the Dow 111 that Stan has recommended in the past for such things.




Oh, I did not know that was possible. Thanks! I think I am good in that respect, as it is just surface corrosion. I did not see any pits. Now, the aluminum timing cover that came off the 3.8L V-6 in one of my old Buick Turbo Regals...that is a different matter.




Hmmm...that is interesting, Chris. I will PM you. Thanks!




Hi Stan! Thanks for the advice. However, the powder coating has been on the pieces for almost 20 years. I'd rather not remove it. All the various intake/water bridge/etc... pieces match.

I have checked the mounting bosses for the temp sensors and the mounting faces for the water bridge to the cylinder heads. They were masked and not powder coated. I performed a continuity check of the crush washer sealing surface for each temp sensor to one of the water bridge to cylinder head mounting faces. 0.4 ohms. Which is probably mostly my leads.
The engine ran fine before I took it apart, so I believe the temp sensors were sending good signals to the computer. PO never reported any running issues of such.

I will definitely use the Dow 111 on all the O-rings. I remember your recommendations from the past. I will not put any on the hose water outlets. Thanks for that heads-up.

I am replacing ALL the coolant hoses and clamps. Starting the clock over for them. I have taken your advice and ordered another thermostat seal for the water bridge. I am a little pissed now, as that seal is only 11 months old...

I have all new bolts for the water bridge mounting. I will coat them in silver antiseize upon installation.

Thanks, Stan!









Got it. Paper gaskets have been ordered, and I will use a thin layer of Reinzosil on each side of the gaskets.
Thanks Sean and Bertrand!




Very good point, Dave. Thanks! As I mentioned above, I checked continuity of the temp sensor mounting bosses. I will take your advice and check continuity to ground once I have installed the water bridge.


Thanks for all your advice, guys!

Roger says Thanks as well. With each new piece of advice, I have to order more parts...

skpyle

Note, all further work done to the engine and accessories on the Red Witch will be documented in this thread:

https://rennlist.com/forums/928-foru...l#post14536481