Bolting a plastic thermostat housing to cylinder head

[garethp]

My brother in law appeared in the drive last night through a cloud of steam, he's got a W reg skoda fabia which now has a thermostat housing with a large hole in the end (it's split wide open and dumped the coolant straight onto the exhaust manifold )

Question is, the housing is plastic with an O ring in the flange which bolts to the head, do I just bolt the new one on or does it need any sealant or lubricant under it?

 

[the snooper]

if it has an o ring, that's all that will be needed

 

[dan.taylor.1]

You could smear a little rtv or similar on it but the o ring is meant to be the seal, if it wasn't they'd provide sealant (though this implies modern dealer parts persons having an ounce of sense..!).

I've fit them in the past dry with no issues.

Dan

 

[rich r]

Usually thermostat housings like that just rely on the O-ring. I put a little tiny bit of grease on the O-ring to hold it in place whilst bolting the housing onto the block. Otherwise it might fall out of the groove and not seal properly.

 

[Rig Pig]

If anything a little smear of silicon grease is all that's needed to help the o ring seat. Make sure that the seal face is spotless.

 

[garethp]

Cheers for the quick replies, I'll give it all a good clean, a dab of grease on the back to stop the o ring dropping out and a quick squirt of silicone spray on the front to help it seat.

Just need to remember to pickup the new housing on the way home!

 

[the snooper]

Cheers for the quick replies, I'll give it all a good clean, a dab of grease on the back to stop the o ring dropping out and a quick squirt of silicone spray on the front to help it seat.

Just need to remember to pickup the new housing on the way home!

make sure the grease you use wont start to degrade the rubber seal if you don't need it its better not to use it

 

[garethp]

make sure the grease you use wont start to degrade the rubber seal if you don't need it its better not to use it

Aw cr9p - didn't think of that. I used a tiny bit of normal grease and the annoying thing is I do have some grease which is definitely safe with rubber. And before anyone asks it was for greasing the forks on a mountain bike I used to have

 

[normspanners]

It'll be fine most o rings are nitrile nowadays so will stand oil/grease

 

[mike os]

Iirc the state clicks into the housing and holds the o ring adequately to install

Do not use grease... use undiluted coolant to lubricate

 

[dan.taylor.1]

Most o-rings or similar seals designed to be used in an engine are fairly tolerant of oils as let's face it an engine without oil isn't going to last very long!

I've always used Vaseline to stick seals and never had an issue.

Dan

 

[rich r]

I'm talking about a smear of grease probably amounting to no more than you'd find trapped under a fingernail - just enough to stop the O-ring coming out. Never had any issues with this method in 20 years or so.