Leaky head gasket

Post by **Benjy** » Wed Oct 08, 2003 5:49 pm

My engine has started spitting oil out between the head and block, just above the spark plugs.

There's no emulsion build up in the rocker cover (unlike last time), so I don't think the gasket has gone too bad yet, but does this mean that oil is getting into the chambers (how?) or is it just being pushed out of the passages by the combustion?

Now I replaced the (copper) gasket about 3 months ago, which was the third time! OK, that time it hadn't gone, I just needed to get at the pushrods etc, but still, 3 times in 18 months is a lot!

Previously a mechanic friend "helping" me with the car overtightened the head bolts by at least 1/2 a turn, probably more "What click?"

. Is this likely to have done any damage? I know a couple of the studs need replacing, but they all torqued down OK last time. Could the head not be seating properly?

Is there anything that is likely to cause head gaskets to keep going? I don't drive the car very hard (most of the time) and it never shows signs of overheating.

Hopefully I'll get a chance to strip it this weekend, so while it's apart is there anything I should be looking for? Any tips would be greatly appreciated, as I'm only really a novice and I'm getting a little tired of rebuilting the top 1/2 of my engine.

Sorry for the long post (I'm getting good at them).

Ben

Post by **rayofleamington** » Wed Oct 08, 2003 7:45 pm

Did you really mean 'just above the spark plugs'??
That wouldn't be the headgasket!

Oil can come from many places, so it pays to find the location before dismantlling...

There are various symptoms of a failed gasket which are worth looking for, and as Willie mentions below - The head should be retorqued after a while anyway.
If it is the gasket and the head is flat and it's not the metal surroundiong the studs, then the block flatness needs to be checked!

Post by **Willie** » Wed Oct 08, 2003 8:14 pm

Assuming that you meant BELOW the spark plugs the only
place where the oil passes through from the block to the head
is right at the front of the engine feeding through no. 1 rocker
pedestal. If the head gasket is leaking here then the oil would
probably be blown back along the engine so that the point of
origin would not be immediately obvious. You could look
for signs of oil in the radiator but the oil may only be seeping
outwards(not towards no.1 cylinder bore). With persistant
gasket failure it would be worth removing all the studs from the
engine block when
you next remove the head and then to LIGHTLY countersink
the stud holes,because,if the head has been seriously over-
tightened in the past, the stud holes may have been raised
which prevents proper seating of the head. The head itself
can be checked by 'swirling' it around on a sheet of PLATE
glass(plate glass is flat)with a thin film of engineers blue or
oil or similar which will show which parts of the head are
touching. It might be easier to get it machined by removing
the least amount necessary to get it flat? One more question,
since you are using the lovely copper head gaskets I hope
that you remembered to retighten the head nuts after a couple
of hundred miles because they bed in. While you are looking
at the studs you can actually see if the threads have been
stretched if seriously overtightened so you may need to buy
some new ones.

Post by **Benjy** » Thu Oct 09, 2003 11:28 am

OK, the oil is definately coming out from the head gasket, which yes Willie is below the plugs - I wasn't thinking, it used to lead round the rocker cover, so I had a picture of oil pooling in the plug wells, but that's now cured.

Erm, nobody told me that copper gaskets bed in

I guess I'll go check the torques before stripping it all down.

When the engines warmed up, I can watch the oil (definately not water) spitting out of the side of the engine. Most of it does appear to be coming from nearer the front, around cyl's 1 & 2. I'll have a look at the plug & see if they're oily.

It sounds like my first course of action should be to retighten the bolts and see how things go. If it's still a problem, at least I'll know for next time!

I know a couple of the stud threads are going, so I'll probably replace most (or all) of them next time it's apart.

Thanks guys

Ben

Post by **Peetee** » Thu Oct 09, 2003 12:03 pm

know a couple of the stud threads are going

With that knowledge I'm a bit worried you may now have a warped head. When you do replace the studs make sure you do all of them. It's good practice and if the problem persists you have then eliminated one possible cause.

Post by **57traveller** » Thu Oct 09, 2003 3:45 pm

I've had a similar problem in the past but only showing up as a slight oil leak at the front righthand side (looking from rear) of the block/cyl. cover in the vicinity of the rocker oil feed holes. Fortunately it WAS just a matter of following up the torques on the nuts when using a copper faced joint.
If there is a chance that the nuts have been overtightened in the past no doubt there is a possibility they have lost their elasticity and/or stretched. On some marine engines I have experienced there is a specific interval, usually running hours of around 20000, when ALL the cylinder cover studs have to be renewed. Try removing them after being in place for 20000 hours.

Post by **Kevin** » Thu Oct 09, 2003 4:43 pm

Try removing them after being in place for 20,000 hours

I wonder how that would translate into mileage.
If you only average 25MPH in a Moggie thats 500,000 Miles or a lifetime whichever is the longer

Post by **rayofleamington** » Thu Oct 09, 2003 5:40 pm

These days, vehicle life is often estimated at >3000 hours (driven) / 10 years (total) - that would be 100,000 miles with an average speed of 33mph. I can't comment on any specific manufacturer, but they each have a different interpretation of this.

Marine engines have a very different life and typically run for higher amount of hours per day - even so, 20,000 hours is a heck of a lot!

Post by **Benjy** » Fri Oct 10, 2003 8:27 am

I've tightened the bolts down and that's stopped the spitting. There's still a slight bubble at the thin point on cly. 1, is this likely to get worse, or should I live with it?

Thanks for all your help

Ben

Post by **57traveller** » Fri Oct 10, 2003 8:34 am

For example - 200 running days/year = 4800 running hours/year, soon mounts up. Not always dependent on hours but could be every three or four years. These bolts or studs have been under permanent tension which increases and decreases with every combustion process.
Similar with a Minor engine's cyl. cover studs. Some of these must be at least 30+ years old, how often has their tension been released and re- applied over time?
In the same vein, bottom (big) end bolts must also be changed, and in my opinion this should be done as a matter of course during an engine rebuild. O.K. this might not be mentioned in any books (Haynes etc.) but it is sound engineering practice.

Post by **Willie** » Fri Oct 10, 2003 6:28 pm

BENJY, that's a difficult question! if there is no oil in the water
and no water in the engine oil then you would appear to only
have a slight leakage of oil towards the outside of the head.
However, if your head nuts are now correctly tightened and
you still have a leak then obviously that is not correct and
when the head comes off you need to find out why you are
not getting a proper seal. The oil pressure should be 60 lbs
per square inch maximum whereas the cylinder pressures
will be considerably higher than this so the fact that the lower
pressure oil is leaking doesn't suggest it will be long before
your problem gets worse. Then again, if you've ever kissed
the Blarney Stone you may get away with it!

Post by **rayofleamington** » Fri Oct 10, 2003 7:00 pm

Benjy,
If it fails, than it was a bad idea - if it last a long time it was a good idea :?

Is there anything that is likely to cause head gaskets to keep going?

From your original question - Yes! As you now know, copper gaskets need to be re-torqued. Also your studs may be close to failing, and stretch more than they are supposed to.
Was your head (and block) checked for flatness on the previous rebuild? I do this everytime (well nearly everytime) as a warped head or distorted block will be very difficult to seal, and prone to gasket failure.

Post by **Peetee** » Fri Oct 10, 2003 7:45 pm

It's a little know fact (well a Vizard one actually) that the engine block can distort. This may be very hard to believe but it's one of the primary reasons the A+ series of engines had strengthening ribs cast into them. The easiest way to distort a block is to torque up worn cylinder head studs and use the car for frequent short journeys.

Post by **Benjy** » Mon Oct 13, 2003 10:13 am

I have never checked the head or block for flatness, I figured that if I didn't do anything stupid (like hit it with a hammer, or drop it) then it'd all be OK. I think I will just have to do the job again (properly) and check everything over.
Better now than in a months time, my garage is free standing and free zing!

Thanks again,

Ben

Post by **Kevin** » Mon Oct 13, 2003 12:05 pm

Previously a mechanic friend "helping" me with the car overtightened the head bolts by at least 1/2 a turn, probably more

I've tightened the bolts down and that's stopped the spitting.

Silly question but you are using the correct torque and in the correct sequence I suppose.

Post by **Benjy** » Mon Oct 13, 2003 4:18 pm

Yes, my friend was used to working on modern engines with higher torque wrench settings and didn't hear the click from my wrench! When I realised he'd been tightening them down for the last 5 minutes I stopped him!

I have since had the head off and on again and tightened down to 40 foot pounds (if memory serves) and in the correct sequence.

Ben

Post by **Cam** » Mon Oct 13, 2003 5:02 pm

I have always tightened mine down to 50-55 foot pounds.

Post by **les** » Tue Oct 14, 2003 9:12 pm

The cooper s head studs with a centre punch mark in the top are useful to use, as they are tougher, and resist stretching better. This could be an alternative to over tightening which could stress the threads in the block.

Post by **Kevin** » Wed Oct 15, 2003 10:06 am

Cam did you use the higher poundage because of the state of tune of your engine as the manuals state 40lb as the norm.

Post by **Cam** » Wed Oct 15, 2003 11:25 am

Yes, but I did my minis (848, 998, 1293) down to about 50 foot pounds also. I think from memory that was what was stated in the manual. If it says to use 40 foot pounds in the Minor manual then that is the figure to use.

Thanks for pointing that out Kevin, I can see that my comment may have caused confusion.