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MG TD TF 1500 - Oil Fill Cap Revisited

I have an oil fill cap issue quite unrelated to the one raised by Gary Kraft.

I am not sure that I have the proper oil fill cap for my car. If this is the correct oil fill cap, I do not know where to find a replacement

My car is an early TF (SS# HDE43/-777) with the original engine. My mechanic tells me that the existing oil fill cap does not fit properly and should be replaced. Unfortunately, the cap I have bears no resemblance to anything I can find in any of the manuals. I have tried to attach pictures of it. It is generally described as a somewhat large chrome dome with lots of breather holes on the underside. I suspect that some oil escapes from those holes.

We tried getting a replacement from Moss Motors but to no avail. We even went so far as to have them send one of each type they have but none of them look like mine.

What oil fill cap should be on my car and where can I get one? I would greatly appreciate any suggestions.

Paul Hejmanowski


P. Hejmanowski

Here is another image of my oil fill cap.


P. Hejmanowski

If it doesn't fit, why would you want another? There is a washable filter element inside, so there is no reason to replace it other than not fitting.

It appears to be an aftermarket (since it is chromed) breather cap, with bayonet fixing (the two-ended bar on the bottom). It was likely an American produced part for something like a small block Chevy, which had such mounting - or any of dozens of other engines that used such. There were probably a few hundred places selling these, sometimes they only fit the valve covers from the same supplier.

Do you have a stock pressed steel cover? If not, it could be a UK or other special to fit the cover. Does the cover have notches for the bayonet fixing?

Finally, does oil escape or not? Not fitting is one issue, but there were literally millions of engines which used this type of cap with no issues; if it fits and blows oil out then the engine is suffering from excessive blowby.

FRM
FR Millmore

FR

My understanding is that the cap is somehow worn such that the mechanic thinks it does not seat as well as it should.

The cover appears to be olriginal (at least it has a prominent MG logo. It has the notches to receive the bayonet fixing.

I am unsure about the possible leak of oil because there is oil on the engine block at that end but this may be from another cause (i.e. leaky seal).

Why would this cap have a breather function when it appears that the original caps did not.

Can you tell that I am mechanically inept?

Paul
P. Hejmanowski

Paul -
Sounds like you are describing a non original cover, probably cast aluminum - no prominent logos on the stock pressed steel one. Could be US, UK, or other,and the cap could be (formerly) common or rare in aftermarket circles. A replacement of the gasket and/or bending of the bayonet tabs should fix the looseness/leak. Original rocker covers were vented to the air filter assembly, aftermarket ones were usually not, so required the vented cap.

Might post a picture - there are plenty on here who would know lots more about aftermarket rocker covers than I.

You are allowed to be mechanically inept, or unschooled, but I'd check out your mechanic again!

FRM
FR Millmore

FRM

Your supposition was correct. I have an aluminum cover without other provision for venting. And now I know why I have such a funny cap. Thanks very much for taking the time to explain it.

Paul
P. Hejmanowski

Paul - The reason that the cap leaks oil from the vent holes around it is that oil is shooting up from the rockers on the engine. As Fletcher stated, this is a cap that was designed to be used on American cars that don't have oil holes in the rockers where oil squirts out. I had the same set up on a TD that we had some time ago and I corrected the problem by installing a small baffle plate just below the filler hole in the aluminum valve cover so that oil didn't squirt directly onto the cap. Cheers - Dave
David DuBois

Dave -
Well designed breather caps of this type can handle reasonable amounts of oil spray. They effectively have their own built in baffles; cheap ones are another story! There is plenty of oil flying around in the rocker covers on most engines, and a correctly put together T should not stand out in this regard. Oil feed is supposed to be intermittent and low pressure here.

The point re baffle plates is worth paying attention to however. Most OE covers have baffles/separators for any hole out of the rocker cover, and most aftermarket ones do not, although they were frequently supplied for installation by the user. Sometimes this was optional, as when the purchaser decided to install a vent such as the one to the air filter. The better aftermarket covers usually had unmachined bosses for the vent holes and the screws to retain the baffles. There was and probably still is a significant industry selling add-on baffled breathers for the guys who threw out the baffles supplied, along with the instruction sheets.

FRM
FR Millmore

Check this from John Twist via Gordon Lawson
http://www.ttalk.info/picture_this.htm#Oil%20Deflector
Bud
Bud Krueger (TD10855)

Look for "Oil Deflector" Bud
[I try to avoid spaces in URLs, but sometimes I just can't avoid 'em. Sorry about that.]
Bud Krueger (TD10855)

Fletcher - What you say is true, but the XPAG engines have an oil squirt hole on the top of each rocker, where oil is squirted out quit vigorously and the after market rocker covers have the filler positioned directly over the squirt hole on number 1 or number 2 rocker. Placing a deflector over the rocker cured the problem of the breather cap dripping oil all over the cover. Cheers - Dave
David DuBois

Dave -
Agreed, I looked at them pitchers! Perfectly located pisser, but splendid little fix.
And they seem to take the rocker feed off the main gallery, rather than the usual intermittent feed.

FRM
FR Millmore

This thread was discussed between 22/08/2011 and 23/08/2011

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