Oil leaks from the Rear Timing Cover - 50690

[David Morris]

Hi there,

As almost every Javelin ( and Jupiter ) owner has realised, the rear timing cover gasket ( 50692 ) seems to have a liking to leak! The top of the engine soon looks messy, and drops of oil appear underneath the car when you stop. Chris Cole and I were wondering if anyone has thought of fitting 'O' rings to the three oil ways in the rear timing cover and dispensing with the traditional gasket entirely? I can hear the gasps from here!

At least two things may make this idea impossible. One is that there may not be enough metal around the oilway holes in the rear cover to allow for the annular rings to be machined to take the 'O' rings. The other is that the four bolts and one stud coming through from the front timing cover may not allow the rear cover to 'drop' sufficiently onto the crankcase, and so allow the 'O' rings to be compressed. One way out of this would be to slightly enlarge the holes...

Has anyone else experimented with this idea? It might be that 'O' rings would be less likely to 'creep' or distort, and so we could, hopefully, end up with dry engines? I believe the JOAC has stocks of a HD gasket, does this solve the problem? Can Javelin owners purchase some?

Please let me know if you have any similar ideas or have tried this yourselves?

All the best,

David

[Keith Clements]

JCCAus has manufactured an aluminium plate that takes O rings and solves the problem. I think Bill Lock will have them available.

[Drummond Black]

The standard gasket is too flexible to do the job proberly. I solved the problem years ago. Hand on heart I can not remember the last time i encountered an oil leak in this area.

The proceedure is as follows :-
Cut a new gasket from a sheet of 1.5 mm hallite ( industrial gasket material used in the compressed air and related industries ) I bought a set of gasket punches to produce to cprrect sizo of holes. Punch the holes FIRST before cutting the profile. ( use a standard Jowett gasket as a template)..

THe two bolt holes that hold the rear timing cover in place require modification. Drill deeper and tap 5/16 BSF ( I will check the max depth from records, however it is nearly double than std. )

Obtain two 5/16 BSF high tensile allen cap screws. Because of the different casting thicknesses at the bolt areas one requires cutting. 50 mm long appears to be correct.

Apply a very light coating of blue halomar gasket compound and assemble . Ensure the small felt at the centre of the VEE is coated in halomar and fitted.

If care is taken your leaks should be a thing of the past.

Drummond

[Drummond Black]

PAT Your comments make sense. During an engine rebuild I always carefully clean the crankcase mating faces and apply a thin film of halomar to the TOP face ( ie . Above the camshaft ). This tends to stop oil leaks in this area.

[PJGD]

Another factor to this oil leakage problem is that the oil filter housing is often distorted, particularly now after so many years. Specifically, the included angle between the two sides (legs) of the filter housing no longer match the top face of the crankcase, having closed up by a few degrees due to overtightening of the two hold-down bolts.

To check for this effect, I advise putting the housing onto the crankcase without a gasket, At this point you will usually observe that the two legs contact the crankcase at the outer ends but a gap exists between them as you move towards the middle. This means that even with a new gasket, sealing will not be uniform across the interface.

Typically, I have to remachine (read file carefully!) one of the legs to rematch the filter housing to the crankcase. That will improve the chance for a leak-free joint.

Philip

[Forumadmin]

The distortion can also occur if the timing cover bolts are too tight. I pinch the housing to crankcase bolts first, then the timing cover bolts, then fully torque the housing to crankcase bolts, leaving the timing cover ones only just gripping. They are threadlocked to avoid loss. I also check the mating beforehand with some contact indicator and scrape off any high points. I do a trial mating with the timing cover and check gap with a feeler guage and use shim washers on top timing bolt. I use silicone rather than paper gasket.

[PJGD]

Well, the "Aus Mod" looks like the business. That should provide a very robust solution to the problem. Are these parts available?

Philip Dingle

[PJGD]

I see no reason why the torque should be any different than is normally applied. The O-ring only keeps the oil in; the dimensional difference between the section (i.e. the sectional diameter) of the O-ring and the aluminium support plate determines the "squeeze" on the seal.

The separating force due to oil pressure between filter housing and crankcase is not substantially changed. Then again, the torque that you can apply is limited by the strength of the threads in the crankcase, so always use the longest thread-engagement bolts that you can find.

Philip.

[Forumadmin]

Clearly you druids down west are also into exorcism!

[TedAllen]

Was browsing some relevant problems and saw the reply from Drummond about elongating the bolt holes. I believe it was poor practise by Jowetts to use BSF threads in aluminium when a chunkier thread would have been better. Also the use of bolts where studs would have done..example..fuel pump fixing, would have solved thread wear.
For the rear timing cover I drilled a pair of scrap engine blocks with a 4mm drill down the fixing holes to see if anything was fouled and where they would come out. There was no problem so I drilled both holes out to 7mm and tapped them with an 8mm bolt which has a coarser thread.
result... a good tight cover and no threads stripped.

[Forumadmin]

This from Leo Bolter who originated it.

When you open the attached picture of the modification, you will notice there are three holes that have the "O" rings inserted in them. This, you’ll remember, is as I described to you the other day. The others are just holes for the hold down bolts of course. The holes in the 16 gauge aluminium gasket replacing plate have been located and shaped so as to be not necessarily round. They are made to a shape which will line up, (and be an appropriate amount bigger) with the combined profile of "rubbings" taken on each side of a piece of paper rubbed onto both the crankcase and the filter housing oilways. This was also done at the same time for the bolt holes and outer edges of both the crankcase and the filter housing. Unfortunately the plate can't be pre-made as this rubbing needs to be done for each engine. There's a number of variations and combinations in both the crankcase and the housing hole sizes and their placement.

When assembling I use a smear of Locktite Gasket Maker on both sides of the plate and "saturate" the carefully made felt that goes in the centreline groove, with RTV rubber gasket maker. The felt is better to be slightly less in volume than too great as it could prevent the plate from seating properly if it "squished" out of the groove on assembly.

Another dodge is to (if necessary) slightly enlarge the 1/4" holes that the bolts pass through in the timing cover so as to be certain that there's no problem in bolting the housing down securely to the crankcase. Check there's sufficient clearance on the 5/16" housing bolts too. As always pre-assembly without the gasket maker is good practice (in more ways than one!)

Also on assembly all the bolts involved in need to be tightened progressively and the plate pushed well against the timing cover before starting to tighten them.

Since doing this mod. to both my cars, there's been NO oil leaks and certainly no blowing out of the stodgy original gasket that has happened previously. I reckon doing this to your Jav will go a long way to fixing that mess all over your engine. As I said, I can't guarantee a complete cure as there could be other leaky places like the crankcase joint at the top centre and around the main crankcase tiebolts nuts etc etc. These are just some of the areas
that are subject to full oil pressure . . . Jav. engine assembly requires LOTS of tricks of the trade, and I think I've got most of them sorted out as the engines I assemble normally DON'T LEAK water or oil to the outside or together!


I hope the above rambling explanation is some help in clarifying what I was talking about.

Cheers,
Leo

[Forumadmin]

I have tried this. So far I have had three attempts, the first two prior to Philip Dingle's article last month in By Jupiter. All have been unsuccessful; but this may be because of incorrect aluminium thickness or O ring thickness or just plain bodged construction! I am attempting to find a source for the 17 gauge alu needed. It seems to be critical to get the amount of crush correct. Too much and the seal squeezes into the hole. Ideally you need a groove in the casing but there is not enough room unless a very slim o ring is used. But that said, there are many successful examples of this mod.

Note the set up had previously failed at least three times with other types of gaskets. I believe the main problem is that, with the larger oil gallery, there is very little gasket material to make the seal. As Phil points out, the holes do not align very well either!

Any one want to put Phil's article in the Gallery?

[Bryan Walker]

Philip Dingle's Article uploaded to gallery.


JowettGallery NZ Jowett Club, Northern Section Bryan Walker Technical Philip Dingle - Filter housing
http://www.jowett.net/gallery/main.php?g2_itemId=2987

Bryan

[Mike Allfrey]

G'dday From The Sunny South,

I noticed in one of the responses mention that the BSF thread is not suitable for use in aluminium. The respondee also advocated coarse threads. Sacrilidge! Bodgerism at its best!

How many Jowett crankcases have been ruined by a complete lack of understanding? Too many to be comfortable about.

One vitally important point - Jowett did get it absolutely right.

I have witnessed those suffering oil leakage at the rear timing cover, doing the very first thing that comes to mind - tighten the bolts further. It never works well. Once there is an oil path, it is best to install a new gasket in the correct manner.

It is not the fault of the thread, it is the fault of the spanner handler!

The poor Hillman Imp went through the same misunderstanding, and that was a real gem of an engine.

I'll get off my banana box now,

Mike Allfrey.

[Forumadmin]

250 mm x 250 mm x 1.2 mm - Sheet - 5251 H22
Specification: 5251 H22
Price:£2.81 (Excluding VAT at 17.5%)


1.2mm is .047inch and exactly the thickness required for pinching the O rings and just 1 thou off the calculated gasket thickness.

http://www.thealuminiumshop.co.uk/acata ... de_32.html

This alu is medium grade and should be suitable. The temper says it is H22 which does not fit in with the scale I use where H2 is quarter hard!

3103 alloy would be weaker and 1050a weaker still, so would not be better support around those bolt holes! 5251 should be used for car bodies. Apparently the strength of the alloy does not necessarily mean it is more malleable; and so take up those imperfections in the Jowett crankcase. Try getting the sheet as annealed temper; rather than half hard.

My catalogue does not list 17 gauge and has 16 gauge at .064inch and 18 gauge at .048inch. So 18 gauge would fit.