Thread: How to stop v8 thermostat housing from leaking?

Originally Posted by Disco_Harvs

Hi all,

No matter what I try I can't seem to stop my 4.6L disco's thermostat housing from leaking. I've tried the following:

1. Three bond only;
2. Three bond on both sides of a paper/fabric gasket; and
3. Paper/fabric gasket only.

The gasket that I'm using is a paper/fabric gasket with a metal inner which has little teeth on it.

The coolant keeps leaking from the bottom of the housing and I'm starting to think that perhaps the inlet manifold or the housing are warped. Is this common?

The surfaces are a little pitted but the three bond would have easily filled these pits.

Is it possible to get the inlet manifold machined whilst still connected to the engine?
I don't really want to take the inlet manifold off as the valley gasket is new and I hate doing that job. I'd also like to avoid getting a new inlet manifold as the current one is modified for direct injection gas.

Any ideas appreciated.

Regards,
Harvs.

It,s more like the thermo stat housing would be warped in my opinion

Would tend to agree with Chris.

To test if the housing is warped - cut out a paper 'gasket' and coat it with paint (water based will do) then just bolt the housing cover on, then remove it - and check to see where there isn't any paint on the housing

If it's not too bad - you could file down the high spots - otherwise get a new housing cover.

Thanks Rangieman and ladas.

Unfortunately this is a new (second hand) thermostat housing which looks pretty good. The old thermostat housing which was badly pitted also leaked in the same spot. I'd like to think it's the housing but I don't like my chances.

I'll certainly try the paper trick though.

Sorry I forgot to mention the other housing.



Harvs.

Some sandpaper on a pain of glass is fantastic to clean up the housing face , it will ensure a flat even gasket face

I have seen thermo stats slip when being fitted with the housing which allows coolant to leak out the bottom of the housing.

A trick i use is a dob of silicon on the edge of the thermo stat to hold it in the resease of the housing while refitting

Brilliant, I'll give the sandpaper and glass a shot.

Any suggestion on what grade of sandpaper to use and anything that I need to look out for? i.e. If I sand back too much will the thermostat stick out too much from its recess?

Also what's the best way to seal the housing once all the sanding is done.

Gasket and liquid gasket?
Liquid gasket only?
Just a gasket?

As for the thermostat slipping and not sealing well lets just say I've been there, said some choice words and learnt from my mistakes. It always gets a dob of sealant these days.

Thanks again for the advice.


Harvs

I use Permatex Ultra Blue Sensor Safe RTV Silicone (sic) Gasket Maker #77B and, usually, a gasket.

It's the duck's nuts as far as I am concerned. Comes in a tube.

Did my water pump, PAS pump and even resealed my dodgy '82 Canter top radiator outlet (no gasket) which nothing else would fix.

Check it out!

Originally Posted by Disco_Harvs

Brilliant, I'll give the sandpaper and glass a shot.

Any suggestion on what grade of sandpaper to use and anything that I need to look out for? i.e. If I sand back too much will the thermostat stick out too much from its recess?

Also what's the best way to seal the housing once all the sanding is done.

Gasket and liquid gasket?
Liquid gasket only?
Just a gasket?

As for the thermostat slipping and not sealing well lets just say I've been there, said some choice words and learnt from my mistakes. It always gets a dob of sealant these days.

Thanks again for the advice.


Harvs

The grade of paper I use is "240 / 320 Wet & Dry" ... Put the full sheet on a flat surface and rub the housing over it (use water) ... Lift it up during rubbing and you will see where it has warped ... Keep rubbing till all shiney (flat surface)

A common problem is that everyone "over tightens" the housing bolts
I use a bottle with brush liquid Aviation gasket gue / non hardening .. Available at Repco or good Auto parts store .... I NEVER use Silicon

Another trick for keeping the thermo in place while fitting is to put a SMALL drop of Super glue to the TOP EDGE of the thermo and glue it to the housing in manifold // DON'T glue the WHOLE AREA // ONLY A SMALL // TINY // DROP

Mike