80 replies to this topic

[mini_pooper]

 Hi all! 

 

Wanted to post a few pictures up here in hope that someone can help with some advice. I have had an engine rebuilt (998cc +20 overbore with pistons, rings etc. to match) and have just finished the first part of running it in (500 miles) and changed the oil. Very sweet running engine and really pulls nicely from the careful driving it has had until now.

 

I noticed however that after torquing the head down to Haynes Manual spec of 68Nm/50 lb.ft and setting the tappets (at the same time as changing the oil at 500 miles), there appears to be a very small seep/weep of coolant coming out from the head/block joint at the head gasket and running down the block in 2-3 places between the head and block, nothing when the engine is warm or bone cold, but seems to be when parked up after a run and when everything is cooling down (I assume as the head and block contract and there's less sealing pressure on the gasket).

 

When I noticed the leak from a couple of spots I checked the head torque again the next day to be safe (completely cold, spiral pattern), and was surprised to find the middle nut of the ones outside the rocker cover and one of the ones next to it (can't remember if it was left or right) was slightly off torque whereas the rest were fine, maybe 1/8th turn of the nut to get it back to torque. Studs are "Y" marked. Took it for a drive this evening, a very minute trickle has come out and have now parked the car to cool completely and see what happens later as it cools.

 

I can see it has a copper gasket fitted and have read here they can be hit and miss unless the block and face are 100% clean. Everything was freshly machined before assembly, and from the quality of the rest of the build I assume it was nice and clean, but you never know if there's something stopping it laying absolutely flat, a burr or a tiny piece of grit... Not sure how big a speck of dust needs to be before the copper gasket has issues   

 

There are no symptoms of any overheating, even in traffic with an electric fan to help the mechanical one when stationary, it has never overheated, there's no white smoke from the exhaust, no rough running (it has a fast road cam but it's not any lumpier now than it has been), nothing in the oil to say coolant is getting in there (mayonnaise), and no drop in coolant level, in fact everything else sounds, looks and feels 100%.

 

I have attached images, hopefully someone has a few suggestions. Either the leak stops by itself (I never rely on this  ) or I'll fit a new gasket to fix it and be safe (I have heard composite is the way to go, suggestions please for the best ones for a 998). However even if weeping is not going to cause issues, I can't have it leaking a few drops all the time as it looks ugly on the freshly painted engine   

 

Does anyone have experience with this type of leak? I have seen pictures of other minis with the same leak patterns down the block, but would prefer to be leak-free for peace of mind! If anyone needs more info I'll answer as best I can   

 

- John

Attached Files

•  IMG_7378.JPG   88.3K   14 downloads
•  Photo 15-04-2018, 16 37 11.jpg   56.4K   13 downloads
•  IMG_5634.JPG   75.11K   12 downloads

Edited by mini_pooper, 16 April 2018 - 06:20 PM.

[carbon]

You mention that the middle nut of the ones outside the rocker cover and one of the ones next to it was slightly off torque whereas the rest were fine, maybe 1/8th turn of the nut to get it back to torque

 

Nice paint work, but was the top face of the cylinder head totally free of any paint under the cylinder head nuts?

 

If not then I would take the 5 'outside' nuts off one at a time and remove all traces of paint. Also clean the underside of the flanged nuts so they are clean & smooth. Then replace and retorque before moving onto the next one.

[mini_pooper]

It's certainly worth checking, there's paint around the nuts, so I can't rule out paint under them (the paint was done when the engine was assembled, not my me) 

 

I assume your theory is that paint under the nuts would cause the nuts to be "lubricated" resulting in the actual torque figure in reality being lower than it should be?

 

Is it advisable/safe to completely loosen only one nut (even if it's just one at a time)? Would be when it's cold of course, just don't want any movement in the head 

[carbon]

Just a suggestion that paint under the nut flanges might give unreliable torque, or could soften off and allow settling of the head hence lower readings after a heat cycle.
 
I have never tried taking off cylinder head nuts one at a time, but if the joint is already weeping then it's not likely to make it any worse. Your other option is to take the head off and start again from square one. Or plan B, stick some Radweld into the radiator (not full amount as the rad capacity is small, about 1/4 bottle should do the trick).

PS. Out of interest where's your engine breather connection to the carbs / inlet?

Edited by carbon, 16 April 2018 - 08:19 PM.

[mini_pooper]

Thanks for the reply, it looks like there may be paint under the nuts, just need to be sure it is "safe" to undo one at a time :)

The breather is vented to atmosphere via a small filter on top of the breather. The engine has had it this way since the rebuild 500 miles ago without a single leak of coolant or loss of one drop of oil, so I can't imagine this has caused the issue of leakage from the head gasket, if that was your trail of thought?

It's an A+ engine so breather comes off the tappet cover at the back of the engine ;)

Edited by mini_pooper, 16 April 2018 - 08:28 PM.

[Rorf]

Time for a new head gasket

[mini_pooper]

Time for a new head gasket

 

Are you able to suggest what type og gasket would be best? Composite type? Brand and source (Minispares) etc.? 

 

Done some searching but most posts recommending gaskets are for 1275cc engines and this is a 1018cc (998+20 overbore) 

[gazza82]

Looked at GUG702506HG ? That's a Payen which have a good reputation.

[mini_pooper]

Looked at GUG702506HG ? That's a Payen which have a good reputation.

Payen has popped up a lot when I was searching the forums as a good, reliable one. Minispares has them and not a huge layout.

I see they also have a "high performance" one for about the same price (C-AEA647), but it's out of stock, is there any benefit to that one, or any composite gasket for that matter, over the genuine Payen Copper gasket as suggested?

I'm completely open to suggestions, but want to be sure it's done once and done right so may as well go for the most bullet proof option from the start! Also have a little prejudice against copper ones at the moment as that's what's fitted and currently leaking, but that's not to say they are completely out of the question! ;)

Edited by mini_pooper, 17 April 2018 - 05:11 PM.

[absx2]

As above, the only gasket to use for trouble free motoring.

When the head comes off make sure the engine builder has slightly countersunk the head stud holes in the block as it is common for the studs to pull and leave a ridge that will effectively keep the head from compressing the gasket properly. 

[mini_pooper]

Good suggestion! Will have a look as and when.

If it's not countersunk, studs should not be too hard to remove (correct me if I'm wrong please) as I believe they are not torqued into the block much? Can't find the figure at the moment...

Just a slight countersink should be enough, with all the oil / coolant passages covered to be safe?

[carbon]

If the cylinder head studs have never been out before they can be tight. But using a couple of nuts locked together to get them out has always worked for me.

 

Has the head been skimmed much? Worth measuring up to see if it is 2.75 inch from deck face to top face, as the thinner the deck face the more likely it is to need careful sealing.

 

And for the engine breather I would recommend fitting a Y-piece plastic adaptor between the two HS2 carbs - just cut the hose joining the two carb breathers and fit there with the third leg of the Y going to the breather on the tappet chest cover (and make sure the rocker cover oil cap has breather hole no larger than about 4mm).

[mini_pooper]

Not sure how much the head has been skimmed but will check when it's off. It's a 12G295 head which I think was Old Stock.

Will plumb the breather to the carbs to get the pressure going the right way and will check the cap, pretty sure the hole is small.

Strange if this pressure caused an external coolant leak though, if that's why you asked, or was it just a "by the way"? :)

From what I can see (unless there is a big internal head gasket failure), there is no way crankcase pressure can affect the coolant pressure unless the A series has a quirk to make this happen?

[sonikk4]

It will be the Copper head gasket. Went through this exact problem and replaced it with a Payen one with no further issues. 

 

I only took the head off my 998 due to its age and wanted to inspect the bores and valves for general cleanliness. Used a Minispares HG set which came with a copper hg and it leaked oil and water. Not badly, just a weep and yes i checked both the block deck and head for true and both were spot on. One full heat cycle for a re torque as well. 

 

Both faces were pristinely clean as well.

 

New Payen HG and instant fix.

[mini_pooper]

Sounds good - is it a Payen Copper gasket you recommend or do they also make a composite one?

If you have an exact part no. that is always best :)