Head gasket ideas

[callyspoy]

Hello folks,
Whilst not normal, is it possible for the headgasket to leak between oil and water galleries, but not get into the chamber?
I noticed my water level was down after the rebuild, so topped up, a bit of mayo in the rocker, but not really used so assumed just condensation as it wasn't a lot.
Checked levels again today and water was low, no signs of leaks, mayo in the rocker, but crucially the oil now appears a bit milky.
It runs well, compression is still very good and even and no signs of of smoking exhaust.
I have all the associated bits to re-do the headgasket (oil, filter, gaskets) and i am well versed in doing them now, but i just wanted a second opinion before i whip it off in the next few days.
Cheers in advance!

[RobThomas]

I'd have expected oil pressure to be high enough to push oil into the water first, if that makes sense. In theory I'd say Yes to the idea but it does sound odd. You'd not lose a lot of water through oil displacing it so maybe that water is actually being forced out by gasses? Any sign of bubbles whilst running at high rpm?

[callyspoy]

Well...it was leaking water at a few places, but at "normal" positions after a rebuild. Thermostat housing, heater outlet, top rad hose.
I did wonder if it was being pressurised.
Well, i'll most likely whip the head off to have a gander. All part of the fun eh!

[oliver90owner]

The cooling system should retain pressure until it cools, after the engine is stopped. That will not be working against oil pressure.

There are few opportunities for oil, under pressure, to be going the other way at any time.

Had a cracked cylinder wall in one engine (not a minor). That was a fairly terminal failure as the water entered the sump.

I expect it is a cylinder head gasket failure. Do you torque the head fixings? Is the head flat? Was the head retorqued correctly?

[geoberni]

Speaking generally and not minor specific, I once had a 910 series Datsun Bluebird (early 80s model) that leaked oil into the water and not vice versa.
Turned out to be a design flaw of oil and waterways in the head being too close and becoming like a porous membrane after a few years, a bit like one of those school science experiments where one fluid can cross a membrane in one direction, but the other fluid can't go the other way.

So anything is possible, I guess it depends if there is a water and oil way close enough for it to happen at the gasket.

(Datsun problem was cured by changing the casting of the alloy head )

[oliver90owner]

Think about this, just a tad. There is only one pressure oil feed to the head and that is at low pressure because all the rocker outlets are not oil tight - so, open ended and do not require any more than a low flow of oil

There are loads of coolant holes in the head gasket and eight push rod holes for any one of them to leak water to oil.

Callyspoy has been a member for over ten years, but that does not necessarily mean he is mechanically minded. There is always a reason why gaskets fail. Usually traceable to something else being wrong, or something done wrong.

Are there core plugs in these heads (can’t remember and not going to look!)? If so, they can leak.

RAB

[les]

I'd be happy to look for you but I know there are no core plugs in the cylinder head. Those in the block are easily seen, (the one at the back is the only one you might need to use a mirror on) although you would have noticed if they were the problem. If you've got all the bits ready, go for the gasket.

[philthehill]

The single core/welch plug at the rear of the small bore block and the twin core/welch plugs at the rear of the large bore blocks are not visible as they are covered by the rear engine plate which hides any problems with the core/welch plugs at the rear of the block. Therefore you would not get any indication that the core/welch plug is leaking.
The only visible core/welch plugs are along the distributer side of the 'A' Series engine.
I have just sold a 1275cc rear engine plate which had two holes drilled through it adjacent to the core/welch plugs which allowed any coolant that has escaped past the core/welch plug to run down inside the bell housing and out through the jiggle pin hole so indicating that one of more core plugs have failed.

[les]

I stand corrected!

[callyspoy]

Aye up folks.
Thanks for the input thus far.
I am quite mechanically minded, hobby mechanic style, but quite confident doing pretty much any jobs automotively.
When i first fitted the engine a couple if months back, i did have an issue of oil leaking from the head gasket from the rocker oil feed at the front of the engine (no not tappet chest cover, nor rocker cover gasket!)
This is with a 12G940 head on a 998cc block, which having looked through the Mini Forum, is not overly uncommon after doing the mod.

Anyway, i confess to reusing the head gasket after slackening off the head bolts and redoing the sequence, as i wanted to be sure the leaking oil issue was sorted before forking out on another gasket. On re-torquing, the oil leak stopped and i have been casually getting the thing running correctly, to the state where it is now driveable and quite fun, which is nice.

But having investigated and found the creamy looking oil, i feel that it is probably the head gasket, even though there are zero symptoms. It runs well, nice high compression on all cylinders, no smoke.
So perhaps the reuse of the head gasket, which i obviously would not recommend, (but it was only supposed to be a temporary measure, hence having replacement ready for the eventuality!) has allowed for some poor sealing somewhere.

Not sure what time i have coming up to get the head off, i am obviously not driving the car at rhe moment though.

[biomed32uk]

I have also been through the oil weeping from the rocker feed area between the head and block, amazing how much can get out through there when hot and blow backwards along the engine.

I had a freshly skimmed block and a true head, decent gaskets, correctly fitted and torqued down etc etc.

2 gaskets did the same, the 3rd one got a very light coat of permatex copper gasket spray. No more weeps and that gasket has now been there for a couple of years without issue.

1st time I have ever used any form of sealant on a head gasket, and there was nothing to be lost in trying it at the time.

[callyspoy]

Interesting about the gasket spray.
I am actually hoping to do the gasket tomorrow. If it happens to leak again, then i will give the sealant a go next.
If it works, it works.
It does seem that that part of the mating face is quite far away from the nearest bolt. Would certainly be helped by an 11 stud head anyway.

[philthehill]

The 12G940 head can easily be converted to ten studs and one bolt or eleven studs as required.
The areas of the 12G940 head where the additional stud and bolt are required to pass through are solid and using a large bore head gasket as a template the holes through the head can be drilled.
Then using the head as the template the holes in the block can be drilled and tapped.
The eleventh fastening at the front of the head can be either stud or bolt but it must only be torqued to 25lbf ft as the top of the block is quite thin in this area.
My own Marina/Ital 1275cc 'A' Plus block and 12G940 head have both been converted to eleven studs without any difficulty or problems.
Use a set of Marina/Ital head studs and flanged nuts and the torque of the head studs/nuts can be increased to advantage.

http://www.minispares.com/product/Class ... c/cylinder head bolt.aspx|Back to search

[callyspoy]

Hello folks,
Did the gasket today, nothing too drastic, appears to have been leaking water into nunber 4 cylinder. Anyhow, all back together and sounds really sweet, reva up freely.
2 annoying things...
1) i was rushing towards the end as i needed to pick up my daughter from nursery, and didn't realise the old oil filter sealing ring (spin on) was still attached. Oil everywhere, bit of a bind! Hey ho!

2)random air lock in the heater. It was working before. Had a look at the back of the heater and the pipe is kinked, really odd that it worked before. So i will remedy that tomorrow by putting a 90° bend pipe on the matrix. I will take the opportunity to flush the matrix out.

So hopefully it will be dreamy by the end of tomorrow, as opposed to creamy!