Thermostat housing gasket take 4! - advice please

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mikeakc

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Evening all,
The saga continues and I'm now on attempt no.4 of reassembling my thermostat housing without a leak. This time I have used JB weld on the steel underbody (which is part of the engine block) and flattened it down with 320 grit paper as there was some damage and minor pitting. I have ordered (another) new cork gasket and treated myself to a new housing lid (the aluminium upper part) as it was fairly pitted and damaged. I can't bear doing this a fifth time so bit the bullet and spent £120 on it.

Before I tackle it this week I have two questions -

1) Last time I used hylomar red on both sides of the cork gasket and cranked it down TIGHT. It still leaked. When I dissembled it I expected the hylomar to have fully vulcanised to a rubbery consistency but it was still fairly gungey (like cheese spread for want of a better comparison!) Incidentally the cork looked very compressed so perhaps I overegged it. I had run the engine up to 100C for 30 mins or so. Should the hylomar red have hardened?

2) When reassembling, how tight should I bear down on the bolts? Just cinched up or pretty firm or very flipping firm? And should I do this immediately after installing or wait a couple of days before tightening (as I would with sikaflex)?

Please excuse me if it seems I'm over-thinking this - I just hope not to have to do this for a fifth time! Thanks in advance for any advice.

Mike
 
mikeakc said:
... treated myself to a new housing lid (the aluminium upper part)... Last time I used hylomar red on both sides of the cork gasket and cranked it down TIGHT. It still leaked...
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I haven't seen/followed your earlier posts about this Mike, so I don't even know what engine you've got, but it strikes me that one possibility is that your aluminium cover is being deformed by over-tightening? I'd expect to get a seal by cinching any bolts/screws down firmly and equally in stages (like a head gasket, say 30 ft/lb) , but not cranking down HARD
 
Hylomar red is semi hardening. For your application I would use the blue Hylomar. It will 'set' a bit more rapidly without a heat cycle.
If the cork gasket looked distorted then it was definitely overtightened. Just tighten until resistance and then nip up slightly more.
 
If you've done it up tight before trying again I would run the face over a sheet of emery on a flat surface, run a marker pen around the face first so you can see how flat it is when it's been rubbed, if the marker is still on the bits between the bolt holes it's deformed.
As Paul says a smear of grease on a cork gasket, more than that needed says the faces are not flat.
 
As above, do not overtighten on a thick cork gasket, you will distort the cover. Cork is very soft and will compress too much.
Using red goo it will squeeze the gasket out when over tightened.
Red goo will not harden, the green used to but is a devil to remove.
I use just a cardboard gasket, usually cut from a cereal packet, and blue Hylomar and have no problems with leaks.
Make sure the alloy housing is flat as snowbird says.
May seem daft but are you sure the persistent leak is not from the hose or elsewhere?
 
Yes @Boater Sam I can see it weeping from the housing. I'll give it a punt now and report back! How long should I leave it before running the engine? The pack doesn't give any guidance on this. Thanks all.
 
mikeakc said:
Yes @Boater Sam I can see it weeping from the housing. I'll give it a punt now and report back! How long should I leave it before running the engine? The pack doesn't give any guidance on this. Thanks all.
Click to expand...

Pack of what ?

Just grease both sides, bolt it down sensibly and that's it. No waiting. It'll seal and you will be able to get it off in the future without damaging the gasket, if you have to. All assuming the mating faces are both flat.
 
The pack of hylomar @BoaterSam . Really I'm trying to make a good job of a pigs ear. Of the three original threaded rods in the housing I have just one operational and original threaded rod. The second is a bolt which has been had it's hole re-tapped in a different thread to the original threaded rod and the third is an original threaded rod which has been fixed in place somehow and can't be removed. This makes it more difficult to flat down the base of the housing accurately (because one of the three bolts remains in situ). Unfortunately the housing sent to me by ASAP (after much photographing and communication with them) didn't match so I'm now using JB Weld to fill and fair the pitting on the mating face of the original housing. What was supposed to be an hour's worth of work has drawn itself out over a month now! Boats hey?!
 
Sorted! Cereal box gasket and blue hylomar did the trick @Boater Sam thanks for that. Turns out the gaskets fro ASAP weren't an exact match and there was enough distortion when stretched between the bolts to leave a gap at one bolthole. Glad to see the back of that saga and thanks to all for the advice.
 
mikeakc said:
Evening all,
The saga continues and I'm now on attempt no.4 of reassembling my thermostat housing without a leak. This time I have used JB weld on the steel underbody (which is part of the engine block) and flattened it down with 320 grit paper as there was some damage and minor pitting. I have ordered (another) new cork gasket and treated myself to a new housing lid (the aluminium upper part) as it was fairly pitted and damaged. I can't bear doing this a fifth time so bit the bullet and spent £120 on it.

Mike
Click to expand...

Did you just make it smooth or did you check the whole surface WAS FLAT using a straight edge?or better still a piece of plate glass.
 
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