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MG Midget and Sprite Technical - New oil leak
|Hi folks, just got the midget back on the road, new rings cured the high oil consumption. After its first 100 miles, all went well except a minor oil leak has appeared on the front/near side corner around the head gasket area. After a retorque of the head and a further run, the leak has moved about 1/2" back under the manifold.|
Could you guys confirm that the two holes in the head gasket at this point are waterways and not oilways?
I am thinking oil may be finding its way down from the rocker cover gasket rather than from the head gasket (its a Payen by the way). What do you think?
1972 1275 RWA Mk III
|The oil comes up from the front cam bearing to feed the rocker shaft in the head.|
Is there an oil trail from the top of the head (rocker cover gasket) down to the manifold gasket? It should be fairly easy to see it if there is.
|Thanks for that Lawrence, I will have a closer look in the morning.|
|Hi, found to be a weeping head gasket (Payen) at the oil transfer hole. Removed the head and thoroughly cleaned the studs, threads and faces etc.|
New head gasket (silver/grey composite) - same problem, marginally worse leak!
As there was no leak here prior to rings and big-end bearings, with the only other symptom being higher oil pressure, now 80 at cold start down to 40 at hot idle. Up from 60 at cold start down to 20 at hot idle.
Would the new big end bearings increase the oil pressure that much, or should I be looking at the pressure relief valve?
Does anyone put any sealant around the oil transfer hole in the head gasket?
The head was skimmed with the unleaded works and the block appears flat (could not get a 2 thou feeler gauge under a straight edge anywhere on it.
What do I do now? - help - getting despondent now.
my gauge (as did the previous gauge) shows from cold start 80, when warmed up 70/75 at normal driving speeds
when warm at idle it shows 40
my engine is pretty near standard
don't get dispondant advice will follow from someone
|My engine did this when it was initially built. I had to take the head off early on and after reinstalling and retorquing it no longer leaked. Actually, I only just realised as I was typing this (I'm a bit slow) but the head had to come off as there was a blockage in the oil feed and I was getting no top end oiling. This may have led to higher pressures there I suppose and probably caused my leak? Anyway, when my engine was leaking there I was told it was not that uncommon, that normally retorquing the head solved it but that some engines just seemed to leak from there no matter what you did, despite new gaskets and block and head being flat?! Seemed odd to me at the time, but it was a highly respected A Series engine builder I was speaking to.|
|Hi, thanks Nigel & Andrew for your comments and support.|
A leak at the oil transfer appears to be a common issue. The head is coming off shortly, I will check any blockage in the oil feed to the rocker shaft.
I was thinking of enlarging the oil-way hole in the gasket and inserting a small rubber O ring with a little sealant to hold in place, once torqued down that should do the trick?
Some say the Payen gasket has a rubber O ring here anyway, however, there does not appear to be one in mine.
Do Metro turbo gaskets have anything special at this point?
|Metro Turbo headgaskets supplied by Payen are the same as the normal payen headgasket so there is no difference. The oil hole is not rubber to the best of my knowledge. The confusion on turbo gasket sets comes from the fact that they have a different manifold gasket in the Payen kit if you can still get it.|
I was not aware of oil leaking in that area as being normal????? I have not known that to be a constant problem, but I am willing to listen to others observations?
|Bob Turbo Midget England|
|IIRC and I'll not be able to check until the weekend, there are 2 very similar looking gaskets.|
BK450 which is the "normal" one and AF470 which looks in all respects identical but has a little rubber seal type thing for that oil feed hole.
There was a recent discussion about a leak associated with that oilway but in that case coming from the brass blanking plug in the head. Being directly above and close to the position of your leak it could easily be the same source. I wonder if yours is in fact the same problem.
The oilway from the block continues through the head by first a vertical drilling, then a horizontal drilling to the first rocker pedestal. The end of the horizontal drilling is closed off with the brass blanking plug on the front corner of the head and these do sometimes leak. It is very close to the gasket join on the head and could be weeping from there. If that is the case then a sharp tap with a punch may spread the plug enough to seal it.
With the head off I would also check that the oilway is clear through to the rocker shaft by blowing it through with an airline, just in case it is blocked with muck and causing a back pressure resulting in your leak.
Good to hear that your new rings have cured the oil consumption problem. Was that with a re-bore, or did you go for the Cords rings?
|Hi all, thanks for your posts.|
Head off now and looking at the oil feed to the rocker shaft, with the rockers/shaft in place, the feed appeared to be blocked (could not get a 2mm drill through to the shaft).
Removed the rockers & shaft and all found to be clear, however, the tiny hole in the (new) shaft does not align with the hole in the pedestal (more than half covered)this must be restricting the oil flow to the rockers and increasing the pressure at the gasket?
The new shaft was from Mini Sport.
Should I enlarge the shaft hole to align? I am thinking the new shaft was a cheap import, already looks like its done 2k miles after only 200! - or is that the lack of oil flow?
Guy - oil consumption solved without a rebore (only 1 thou. of wear on the cylinders) the rings were knackered, particularly the oil control. Just needed a light hone and new standard rings. Did not use Cords on the advice from local engineer, too harsh and would just speed-up the need for a full rebore.
|Thanks for that info on your ring cure Tony. Its a job I need to investigate when the weather gets a bit drier and warmer!|
When I replaced my rocker shaft a while ago, I am sure that the edge of the oil feed-in hole in the shaft was chamfered to help alignment with the feed through the pedestal. Yours not like that?
|Hi guy, here are some pics. Yes oil hole is slightly chamfered on the shaft, however, the hole is 15 deg. out of alignment from vertical.|
1st pic. Shaft vertical as fixed to pedestal, hole with 2.5mm drill is 15 degrees out.
|2nd pic, shows underside of shaft with slight chamfer and wear to shaft after 200 miles.|
|Third pic shows the inside of pedestal (3mm hole) with no chamfer.
I am no expert at all, but I kept my old rocker shaft and have just got it to take a look.
The oil feed hole is indeed offset radially by about 15 degrees when compared to the row of feed holes out to the individual rockers. I think this is because they feed out slightly away from the direct underside which is where the greatest upward pressure exerted by the rocker would be.
The oil feed hole on mine is drilled right through to the top of the shaft. And this feed hole on the upper side is aligned perfectly to the hole for the locating screw on pedestal #2. in other word both holes are drilled truly vertical so that the feed hole aligns with the input gallery in pedestal #1
Does that help for comparison purposes? I could photograph if that helps.
I just checked the oil feed hole size. A 2.5mm drill passes quite easily, and rocks slightly in the hole. A 3mm drill won't fit. So somewhere between the two. Given that it should be an imperial measure the closest I can find by calculation is 7/64" which would apparently be 2.78mm which would be about right for the amount of slack I can feel.
Looking at this shaft I am surprised at the amount of apparent wear on the upper side of the thing where it passes through the pedestals.Almost the same as the underside where the rockers move. - given that the shaft it is static there, not rotating, it must be just the continual hammer effect.
|If the length of the shaft and all the rockers were getting oil (you would see if it was running dry, even after only 200 miles), there can't have been excess oil presure at that point, so I doubt this is the cause of your hg oil weep.|
Even if the oil hole was blocked completetely the oil pressure shouldn't cause a leak out of the hg. The copper reinforcing ring on the hg is presumably there to contain the extra pressure at that point.
If it was coming out due to pressure, you would see it emerge as a trickle of oil, rather than a weep, when the engine was running.
I've been raking through my memories, and I too have heard of adding sealant at that point to prevent oil weeping out, but I don't think it's a common problem.
I've never heard of using a rubber O ring. I think that would be too thick, and unless you used the right heat resistant type, I wouldn't think it would last long.
Examine the surface of the block as well as the recently skimmed head. Lay the head on the block without the hg, and see what sort of gap there is, if any at all, at the point around the oil feed in question.
As for sealant, I wouldn't usually use one on a hg mysef, but there seems to be a debate about that these days.
For this purpose, I was going to say Red Hermetite, but it's now been replaced by Hylotyte Red,, made by the same mob as Hylomar Blue. Looks like the same stuff, and I reckon it will solve the problem, and certainly won't do any harm around an oil or water way at the edge of the head.
2 quid on the web, and presumably not much more in car spares shop.
|Hi Guy, thanks for looking, a comparison photo would be great.|
The picture below of mine, shows the lower (2.5mm) hole does not align with the upper hole (larger and the same size as the no.2 pedestal lockating hole)
I think I may be getting to the bottom of the problem!
|Time out beat me.|
This is an edit of my last post.
I meant to say the old discontinued Gold Hermetite, but it's now been replaced by Hylotyte Red, its semi setting and hi temp resistant. I reckon it will solve the problem if a smear is added top an bottom of the copper ring on hg at the oil hole in question.
See the earlier post to make sense of this one.
|OrangeSpyderman is correct - there are two Payen gaskets identical in all respects other than one has a rubber sealing ring around the oilway. I'd try that version before anything else.|
|Chris H (1970 Midget 1275)|
I rather agree with Lawrence, I am not at all sure that the oil weep is anything to do with the rocker shaft. But you may as well check that all is well with the oil feeds to that anyway, whilst you have it apart.
Here is a photo of my rocker shaft. The nearest black drill is a 2.5 mm through the oil supply hole that aligns with the feed in pedestal #1. I would say that the hole is drilled at a pretty accurate diagonal to the shaft
Beyond that is a silver drill through one of the oil to rocker feed holes. Clearly at a different angle, maybe 15 or 20 degrees.
The fatter gold drill is inserted into the locating hole and is parallel to the black drill.
I think it was in Vizard, the A series bible, that it was mentioned that the OE rocker shafts were soft and the aftermarket cheap ones worse leading to wear. You can buy or could buy hardened rocker shafts and I bought one from one of the usual suspect mini suppliers years ago and it seemed to stand up very well even with a higher lift cam and stronger springs. I did rebush the pressed steel rockers I was using though so the bushes were a good fit, worn bushes on a new shaft would lead to accelerated wear of the shaft.
|And here is a close up of the oil feed entry hole, with 2.5mm drill, but shows the chamfer, much the same as yours.|
It also aligns with the split pin hole at the end, although this cannot be critical!
|I had the same head weep from the oil feed on a freshly rebuilt motor + skimmed head + all new shaft and rockers. Retorquing made no difference so the head was pulled and I used Stag Wellseal on the transfer hole. Problem solved.|
|My thanks to Guy, Lawrence and everyone who posted.|
Your photos Guy prove to me that your oil supply hole aligns perfectly with the hole in your pedestal, mine on the other hand is way out and is only allowing about 20% of the oilway area, with the premature wear too, I will correct this with a new shaft. However, do agree that this is unlikely to contribute much to the oil leakage.
I will also go for a Payen AF470 (with the rubber O ring seal). Maybe even a smear of sealant around the oilway too! Removing the head three times in a week is no joke.
Just cleaned up the head and block faces and placed the head back without a gasket, can't get a 2 thou. feeler in anywhere.
|Do you have a strong focussed torch beam, that you can shine through -- at the corner -- of the block and head mating surface, whilst looking at the other side. |
This might give you a clue.
Either you've had 2 bad hgaskets, or there is a very small uneveness in the corner of the block/head mating faces at the oil way.
But there you go, Fergus has had the same thing and solved it, so I'd give that a try for sure.
|I just googled Stag Wellseal, as I had not heard of that stuff before. This is what is said about it here.|
Developed by Rolls Royce Ltd and manufactured under license, this compound is the complete answer to sealing problems on machined faces.
Stag Wellseal jointing compound is non-flammable, has easy partability and is non-hardening it is formulated to give the best possible sealing
performance under a wide variety of conditions.
It can be used to seal threaded connections as well as flat- faced joints and can be used with or without a gasket, depending upon the design of the assembly.
Stag Wellseal Jointing Compound is highly resistant to the majority of commonly
used field, lubricants and coolants and is non-corrosive and free from
Wellseal will withstand temperatures up to 195?C (383?F)
After two head gasket failures within the week, block flatness was suspect.
After fiddling about with straight edges, bright lights, mirrors and feeler gauges, I tried the following:-
Using an off-cut of thick float glass (£1 from our local glass merchant) slightly larger than the block face, I covered one face with blue permanant marker pen. Once dry and under its own weight, I moved it slightly up and down on the block. The high spots became obvious (the blue just rubs off) round the majority of the stud holes and along the edge of block, forward of the oilway.
With 600 grade wet&dry, lightly oiled and a smaller piece of glass, I flattened the high spots. After a thorough clean-up, I used the glass trick again - all flat!
Looks like the studs may have been over-tightened in the past - the rocker shaft oilway alignment maybe was a red herring, although the oil pressure has now reduced to what it was before.
With a Payen AF470, which has a rubber O ring set in the oilway joint and new studs and new better quality rocker shaft - the job was done.
Thanks for all your help & support.
|is that blueprinting ?|
|"is that blueprinting ?"|
Or were you joking?
|Robert (Bob) Midget Turbo|
|sorry Bob I meant blue inking :)|
|Hi, whatever its called, it works!|
|sorry Tony just had to see who'd jump at my comment first :)|
using a flat sheet of glass or mirror to check for true was a quick check I remember being told about
This thread was discussed between 07/01/2012 and 15/01/2012
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