Sq4 MKI blown head gasket

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Gui.dorey
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Sq4 MKI blown head gasket

Postby Gui.dorey » Sun Mar 29, 2020 11:32 am

Well Chaps, my season did not start too well.

After servicing my square four, adjusting valves, etc, wanted to go for a short ride to see how everything was, and didn't really past the driveway. Noticed immediately that there was a blow by at the rear of No 3.

This morning took the head out, and my almost new Otto gaskets are blown. At the rear of No 3 it actually burned a piece off, at the rear of No 2 the gasket material was eroded and one can already see the inner metal core. The mileage is maybe about 500km....

So what are your thoughts on this? Head not torqued properly? something else? It also looks like No 2 is running cooler or richer that the other 3 as it has a lot more soot and looks blacker.

Next question - where can I get some new Ottos?

Cheers,
Gui
Attachments
No3_LI.jpg
No2 Barrel_LI.jpg
No2 _LI.jpg
No 3 barrel b_LI.jpg
Head_LI.jpg

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simon.holyfield
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Re: Sq4 MKI blown head gasket

Postby simon.holyfield » Sun Mar 29, 2020 11:37 am

Those are in the worst place for spanner access aren't they. Have a look at the surfaces, make sure they are flat but I'd suspect a torque issue. I was amazed at how much mine loosened at the back.
cheers

Simes

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markus.nikot
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Re: Sq4 MKI blown head gasket

Postby markus.nikot » Sun Mar 29, 2020 2:54 pm

Never seen this on a Otto equipped Square. Could be a torque or surface thing.

After fitting a SQ4 head, I run it for some (5)minutes in the workshop, let it cool down and retorque. Here you'll find a lot of setting. Than 50-100 moderate km - retorque, 3-500 more km and retorque, and always, dont't forget checking the valve clearance.
This workes on my Squares for many tkm.

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roger.fellows
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Re: Sq4 MKI blown head gasket

Postby roger.fellows » Sun Mar 29, 2020 3:10 pm

Has somebody not quite skimmed the block or head enough?

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Re: Sq4 MKI blown head gasket

Postby Mick D » Sun Mar 29, 2020 3:37 pm

Hi

Is it an anomaly with the photo or is there an area of cylinder block face missing where you have circled and annotated No 3?

This would be co-incident with where the blow past / damage to the gasket occurred and probably the cause of it.

I wouldn't be confident that a new gasket won't be ruined in a short time unless this face is restored.

Regards Mick

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Re: Sq4 MKI blown head gasket

Postby JohnnyBeckett » Sun Mar 29, 2020 3:54 pm

if the head gasket is copper i think the faces are not flat can you not get a thicker copper gasket made :?:

Gui.dorey
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Re: Sq4 MKI blown head gasket

Postby Gui.dorey » Sun Mar 29, 2020 6:57 pm

Mick D wrote:Hi

Is it an anomaly with the photo or is there an area of cylinder block face missing where you have circled and annotated No 3?

This would be co-incident with where the blow past / damage to the gasket occurred and probably the cause of it.

I wouldn't be confident that a new gasket won't be ruined in a short time unless this face is restored.

Regards Mick


It's just the picture and soot. The faces of both barrel and head re flat. I checked them again with a metal straight edge just to make sure nothing had warped, and it is still perfectly flat.

What does everyone think about how the combustion chambers look and the difference in No 2 in relation to the others? Anything to worry about or all acceptable?

Cheers
Gui

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Re: Sq4 MKI blown head gasket

Postby daveleek » Sun Mar 29, 2020 7:52 pm

Are any of your cylinder liners protruding above surface , it looks like a bad crack in photo 4 to the left . I had oil leak problems that I couldnt cure , I had the head and barrel skimmed , head was warped and 2 liners were above the surface , just done 100 miles retorqued twice and its oiltight at the moment , there is no lock-down here thankfully [at the moment] I only put RTV around the push-rod tunnels [ Permatex HT]suposedly a higher temperature rating than the Loctite product , an old-boy once told me not to use silicone on a head gasket because its super slippery ,blimey Ime now an old-boy. It appears that once your rtv had deteriated through heat the compression had an easy escape route,
It seems there are a lot of contributing factors there.

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Re: Sq4 MKI blown head gasket

Postby JohnnyBeckett » Sun Mar 29, 2020 8:09 pm

Number 2 might have had misfire and it was washing the head

Gui.dorey
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Re: Sq4 MKI blown head gasket

Postby Gui.dorey » Mon Mar 30, 2020 8:22 am

daveleek wrote:Are any of your cylinder liners protruding above surface , it looks like a bad crack in photo 4 to the left . I had oil leak problems that I couldnt cure , I had the head and barrel skimmed , head was warped and 2 liners were above the surface , just done 100 miles retorqued twice and its oiltight at the moment , there is no lock-down here thankfully [at the moment] I only put RTV around the push-rod tunnels [ Permatex HT]suposedly a higher temperature rating than the Loctite product , an old-boy once told me not to use silicone on a head gasket because its super slippery ,blimey Ime now an old-boy. It appears that once your rtv had deteriated through heat the compression had an easy escape route,
It seems there are a lot of contributing factors there.


There is indeed a crack but it is not bad. It's actually only the fin from a heavy handed PO, but fortunately doesn't go into the sealing surface.
As far as the liners, they are all even with the surface.
One point could be the sealant. I did use Loctite ultra Copper, but I did smear a bit along the whole gasket sutrface, and not just a bead around the push rod tunnels. That along with not properly torqued nuts around the rear - especially the two under the manifold, could have led to this....


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