Jeff928S4

Coolant leak on a 1989 S4

At first I was accumulating coolent in the small alcove below hose #19......(see pic below)

I thought it was the hose itself and Garth S. gave me a replacement to try. Replaced the hose and now I have what seems to be a bigger leak, but it isn't puddling in the alcove anymore, but rather it is leaking in the area under the fuel damper (#6). Perhaps I had two leaks and the swapping of the hose stopped one, and amplified the other?

I noticed a large circular thing that sits in this area and it appears to be leaking out of this area. The "circular" thing appears to be right below where the thermostat sits.

Now, when I order a new termostat, inner housing seal and O-ring, will these be the only parts that could be faultly, thus causing a leak in that area? I'm not sure how the thermostat sits and where the seal/o-ring end up.

Thanks!

ErnestSw

The O ring sits outside the thermostat and the housing presses against it when tightened. Do yourself a favor and loosen the fitting to the fuel damper before you try to remove the thermostat housing. It makes the bottom bolt accessable.

Garth S

Hi Jeff,
The parts you refer to all stuff in behind item #17: The source of the 'new' leak would be from the thermostat bridge ... to which the T-stat housing #17 bolts to. There is a gasket to either head and a large O-ring on the bottom. The latter would fit your description. The bolts to the heads are tricky to remove ..

AJK

This may not be correct since I have a '79, but right below the thermostat housing and part of the same casting is a large (3.5 inch) circular passage that is sealed to the block with an O ring. Mine let go last month and sorry to say it is a real PITA to replace.

Jeff928S4

Now is this O-ring the one I mentioned or it is a separate part.....pardon my confusion, it's Friday.

ErnestSw

I THINK Garth is saying that it's the coolant housing BEHIND the thermostat housing that's leaking.

Jeff928S4

That would make total sense, as the leak appears to be coming from below the thermostat housing, yet there is no sign of coolant anywhere near where the housing itself sits....it's lower, around the large circular thing I mentioned.

tv

What they are saying seems correct. I just looked at my spare engines bridge which is off for cleaning. It has 2 gaskets for joing to the heads and 1 black rubber round gasket for mating to the front block water inlet.

Garth S

You need the 83 deg C thermostat, front O-ring and rear seal - p/n's 928 106 129 16, 999 701 632 40, and 928 106 163 00 to R&R the parts behind the T-stat housing (#17).
For the leak, you need o-ring 999 701 627 40 ( 53x7mm) and two of gasket 928 106 227 00. It would be a good idea to also order the allan head bolts that secure the bridge - count on breaking at least one ....
Earnest 'thunk' correctly ... it is the thermostat bridge piece, specifically the O-ring seal that appears to be the leaker.
Start soaking the 4 bridge bolts in penetrant any time soon .... is we want to see it apart by spring

Jeff928S4