G'day, I am having HEAPS of trouble getting the thermostat housing on my EF 5 litre to seal. I reckon I must've tried 10 times to get it to seal, no luck yet, still leaking, I am running out of ideas. I have an explorer manifold off an AU XR8, do these run a different thermostat housing? Still running one off an EB-EL

What I've tried:

Cleaning both surfaces till they are SPOTLESS, and fitting the thermostat housing with a new gasket, and no sealant

Cleaning both surfaces till they are SPOTLESS, and fitting the thermostat housing with a new gasket, and PLENTY of sealant on BOTH sides of the Gasket (Ultra blue or Blue Maxx has been my chosen sealant)

Getting the thermostat housing LINISHED by the local engineering shop, and cleaning the manifold surface until it is SPOTLESS, and fitting it with a new gasket and no sealant (this is where I am at now)

What I have NOT YET tried:

I haven't tried removing the thermostat, to see if it's dropping down and wedging the thermostat housing apart some how

I haven't tried using ONLY Ultra blue and NO gasket

I haven't tried using 2 gaskets

I haven't yet tried a BRAND NEW thermostat housing, but I've tried quite a few 2nd hand ones

Any more ideas will be appreciated.

Gab

I had similar issues on my AU windsor. What I ended up doing was not using a gasket, only sealer and running a piece of string through the radiator hose hole around the thermostat to hold it tight in place while i lined it up and bolted it on. Then once I'd done that I pulled the piece of string out and it never leaked again. This may or may not be the answer to your issue but hopefully it helps.

Try putting a straight edge across the housing surface. If the surface is not flat, you'll get leaks. I had the same problem with an aftermarket thermostat housing on my AU. Also check the surface on the block.

+1 for EF_nut's suggestion for a silicon gasket/seal.