20 replies to this topic

[Spider]

For Thermostat Housings, I've tried many, including Hylomar, which is good, but I found an name brand RTV to be better.

[beardylondon]

Thanks. Just to confirm I’m taking about this stuff, not the regular stuff they sell in motor factors.

This is meant to be closer to the original formula and that Rolls Royce still use

https://hylomar.com/...aerograde-pl32/

[weef]

In the main the sealing of the thermostat housing is quite straightforward, but when there is a leak, be it on the joint faces or leaking up the stud holes it's a right pain.

Initally ensure the mating faces are flat and clean, the stud holes of the thermostat housing are not corroded or worn through corrosion and the studs are similarly clean and showing no sighs of deteriation. Renew any components that appear to be not fit for purpose.

Hylomar, probably the medium grade, or a brand name RTV compound will be suitable to use as a sealing compound.

Unscrew the studs and refit using a little sealer on the threads, nipping them tight.

Lightly coat the mating faces with the compound of your choice and assemble the components in order and tighten up, taking care not to overtighten, leave the joint to cure before you fill with coolant.

There is no need to use excessive amounts of sealer as it just squeezes out everywhere and just leaves a mess, less is better.

[mbolt998]

What about using a paper gasket and smearing a bit of Hylomar on it as well? It shouldn't be necessary but seems like it might be worth a try if you have problems with a leak.

[beardylondon]

This is exactly what I’ve been doing for years. I have been searching online for better stuff and hence this aero grade version came up, so I thought it might help.

In the main the sealing of the thermostat housing is quite straightforward, but when there is a leak, be it on the joint faces or leaking up the stud holes it's a right pain.
Initally ensure the mating faces are flat and clean, the stud holes of the thermostat housing are not corroded or worn through corrosion and the studs are similarly clean and showing no sighs of deteriation. Renew any components that appear to be not fit for purpose.
Hylomar, probably the medium grade, or a brand name RTV compound will be suitable to use as a sealing compound.
Unscrew the studs and refit using a little sealer on the threads, nipping them tight.
Lightly coat the mating faces with the compound of your choice and assemble the components in order and tighten up, taking care not to overtighten, leave the joint to cure before you fill with coolant.
There is no need to use excessive amounts of sealer as it just squeezes out everywhere and just leaves a mess, less is better.

[GraemeC]

Use a good old fashioned thick cork gasket - it will deform much better to fill any gaps.

 

But before that - check the fit of the thermostat in its groove and whether or not it is causing the housing to lift and not snug down properly - I've had this on a head that had had the top surface skimmed