MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Tappet Chest Oil Weep

Guys,

Does anyone have a trick / method for accessing & nipping up the rear tappet chest without having to remove the exhaust manifold? I have a slight weep of oil that i think is coming from there.(The front one seems as dry as a bone). I put new gaskets on both tappet chests in 2017 (after removing the carbs & manifold) due to a constant dribble of oil from the rear one. I replaced then using a cork one at the front with a silicone / rubber at the rear (i recall John Twist recommending that approach). I would obviously prefer to try & see if nipping it up a bit solves the issue first before having to take the manifold etc. off again! I appreciate that it shouldn't be tightened up too much.
Cheers,
Charles
Charles9

Charles,
sorry no tip but I was wondering if you overtighten it might distort the cover by pulling the middle in and loosen the perimeter seal.

Also if you're not sure where the oil leak originates you'd probably be best to clean the engine, and bay, and then see where oil shows up as gravity and the engine and car running can play tricks.

You can very quickly and very easily clean (and leave polish finish) by cleaning with Autoglym 'Engine & Machine Cleaner' and "Follow with Vinyl & Rubber Care to dress your engine bay with a satin sheen".

See 'How To Use' tab here -https://www.autoglym.com/engine-machine-cleaner

Also see this video, I've been doing this on various cars for decades, I clingfilm over just the electronics as belt and braces but as everything is done at low pressure and the electronic dissy on mine should be protected by the cap and good quality HT lead boots I might not even bother if it was CB points. - https://www.youtube.com/watch?v=JW1PisYwWJI

Slightly more and thorough detail vid here (as my car is always outside I never bother with step 5, I'm all about spray and walk away). - https://www.youtube.com/watch?v=xN_C1cP5rdY
Nigel Atkins

Nigel,
Thanks for your feedback.My engine bay is just about as clean as it would have been as it came out of the factory with the engine block on the distributor side as well. Behind the exhaust manifold it is oil dry round & below the front tappet chest cover but oily below the rear tappet chest with oil sitting on the bottom ledge. I use the Autoglym products you refer to & rate them as you do!
I'm just trying to save myself the hassle of removing the carbs,heat shield & so on !
Cheers,
Charles
Charles9

Charles-
Your problem may not be a gasket leak. The rubber grommets (BMC Part # 12A 1176, Moss Motors Part # 324-335) and their cup washers (BMC Part # 12A 1177, Moss Motors Part # 324-325) on the fasteners tend to both take a set and harden when left in place over a protracted period of time. Therefore, always replace them with new ones in order to obtain an effective seal. This is very important because many tappet chest cover leaks originate at the mounting hole of the tappet chest covers. The cup washer allows the rubber grommet to compress and seal while simultaneously containing it, so that it does not merely broaden outward and not perform its function of sealing as well as it might if it were confined. Interestingly, the cup washers seem to be one the most-often missing items on a B-Series engine.
Stephen Strange

Hi Stephen,
Thanks for your comments.i was in fact aware of the cup washer & rubber seal grommets issue when i reafixed the tappet covers 4 years ago & used new ones & screw bolts. All the more annoying that i appear to have this oil weep frmm the rear one. ( I have already placed an order for further replacements if I can't just nip the cover up a bit without having to remove the carbs,heat shield & probably the exhaust manifold again!)
Cheers, Charles
Charles9

I did change mine by removing the carbs but not the (cast iron, others may differ) exhaust manifold. Careful orientation got them in without the surfaces touching anything on the way. As I recall at least one of them had to be fed in with the bolt already fitted as it couldn't be fitted afterwards, or something like that.

There are two different types of gasket - cork and rubber - that go with different covers and the covers changed at various times, the gasket faces are very different and obvious. I've read that Gold Seal rebuilt engines used covers taking the rubber gasket at the rear and cork gasket at the front, and that is what mine has. There are also two thicknesses of cork gasket. I think I received the thinner ones, I don't know if thicker cause a clearance issue.

I also replaced the rubber washers as per Stephen, the cup washers ensure the washer seals to the threads of the bolt as well as the obvious surfaces. Mine (1973) have the same on both covers although the pre-77 Parts Catalogue shows them only on the rear with a copper washer on the front. The 77 and later shows a quantity of 2.

They have been oil-tight for a few years now.
paulh4

Hi Paul,
Thanks for your comments - as i said in my various posts, i used a cork gasket at the front ( i recall it being the MGA type as recommended by John Twist & rubber at the rear together with new cup washers , rubber seals & bolts on both). I suspect part of the issue may be the "rubber element" that is not as pliable as of old, particularly when new. (I know we have all had issues with rubber components for various parts of our cars).(I found this when using new rubber grommets that are inserted in the top of the rocker cover box,the nuts & bolts of which had to be tightened a couple of times after one or two heat cycles to ensure no oil leaks from the base of the rocker cover where it meets the head). This might apply to the rear tappet chest which has both the rubber gasket & rubber seal to contend with, although i am conscious of not wanting to over tighten and then lift the edges away. I did use a smear of ThreeBond Plus Liquid gasket on both tappet chest gaskets which has been very effective elsewhere (e.g. water pump & heater valve mating to block).
I read your paras on your website with interest!
Cheers,
Charles
Charles9

Charles,
sorry I should have put something like, if not already done, I had an idea that your engine bay might be clean.

I very rarely clean my engine bay but when I do I find it very soon gets very dusty/gritty/dirty again possibly with use and because it stands outside 365/6.

Something at the back of my mind is thinking modern rubber seals are not quite the best fit and get tight at the corner(s) (?) - but you'd know from when you fitted it.

The thing with the JT idea is that whilst good it may relate to that time and/or USA rather than UK parts quality.

I know how you feel as nearly a year ago I was taking my manifold and carbs off and apart and back on so many times I developed a quick technique, forgot most of it now of course.
Nigel Atkins

For others approaching this one problem with the rubber gasket I forgot to mention was that it was too small for the groove in the cover! I had to clamp it to the cover overnight, then quickly un-clamp and fit while it stayed in position. If I clamped it for a shorter period it soon popped out.


paulh4

If you do want to try and nip up the rear tappet chest cover bolt to see if the weep stops, then this can be done using the ring end of a combination spanner. Make sure that the engine is cold and then you can get onto the bolt from underneath the heat shield and exhaust manifold.

Be very careful not to overtighten the bolt as that could just distort the cover and make the leak worse. Just slightly tightening the bolt worked for me.

Andy
Andy Robinson

Thanks Guys !

Paul - did you fit the rear rubber gasket dry without using any sealant on it and also the cup washer & rubber seal including any thread seal on the bolt?

Cheers,
Charles
Charles9

Charles - I used a smear of non-hardening sealant on both faces of the cork gasket but nothing on the rubber gasket nor either washer.
paulh4

Thanks Paul,
Maybe that's where i made a mistake with the rear cover!
Cheers
Charles
Charles9

I've also had problems with the rubber gaskets being too small. I've tried gluing the rubber gasket to the cover but with variable degrees of success. I agree that if you remove the carbs you can change the gasket with the exhaust manifold in place but its a fiddly job. (finding the female threads) Also you should be able to give the centre fixing a tweak from underneath.
Paul Hollingworth

Thanks Paul H,
I've had a go this pm. With just the air filters removed & using a stepped combination spanner managed to get a purchase on the bolt holding the rear chest cover (which takes a lot of patience as you can't see , but only feel)! I was surprised how loose it was & carefully tightened it up , resisting the temptation to over do it. I shall take the car for a run ,assuming the dry weather holds & see if i done enough to stop the weep.
Cheers,
Charles
Charles9

"you can't see , but only feel"

There's quite a lot of that on the MGB, I find closing my eyes helps!
paulh4

Guys,
There is an MG God. After a spirited drive yesterday i parked the car in it's usual plzce over a clean drip tray & have just checked this am. Only a smudge of oil in the place where previously there was quite a pool of oil! Hopefully the problem has been easily sorted.
That smudge might just be residul oil dripping off the block.Whatever- i can live with that,afterall aren't old British cars known to leave their calling card.
Thanks to all.
Cheers,
Charles
Charles9

Well done Charles.
Nigel Atkins

Yes, a car from the 60s and 70s that doesn't drip a little probably has no oil in it. These days manufacturers fit under-engine trays so you can't tell if they drip!
Mike Howlett

This thread was discussed between 19/04/2021 and 23/04/2021

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.