940 Distributor Cap -- Needs a Gasket?

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gsnieder@canspec.com - 17 Jul 2005 00:35 GMT

Dear NG:
I replaced the cap, maybe the original, at 250k km and found it to be
full of black powder and some oil. Shouldn't this part require a
gasket or seal?
TIA,
H2Only

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Randy G. - 17 Jul 2005 02:10 GMT

>Dear NG:
>I replaced the cap, maybe the original, at 250k km and found it to be
>full of black powder and some oil. Shouldn't this part require a
>gasket or seal?
>TIA,
>H2Only

The cap shpould be replaced at regular intervals on any car, and that
is more true with electronic, high-energy ignition systems. The
atmosphere in the cap area is prone to condensation and eventually
this causes carbon tracking- an arcing across the cap inside that
leaves carbonized trails that conduct some of the energy to other
spark plugs- one cause of mis-firing.

Most distributors are actually vented becasue the wide range of
temperatures to which they are subjected precludes sealing them
completely. They also need to be lubricated, so the bore in teh block
is usually lubed with engine oil, and if the distributor is well worn
oil can get into them. If the distributor has a mechanical advance
mechanism this too needs to be lubricated, and if not done with a
heavy oil this can spray about. If the distributor has points, the cam
needs lubrication and this can splatter as well if the correct lube is
not used.
__ __
Randy & \ \/ /alerie's
\__/olvo
'93 960 Estate

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James Sweet - 17 Jul 2005 03:21 GMT

> Dear NG:
> I replaced the cap, maybe the original, at 250k km and found it to be
> full of black powder and some oil. Shouldn't this part require a
> gasket or seal?
> TIA,
> H2Only

The black powder is from the carbon center contact, normally the cap is
replaced before it builds up to that extent. There isn't a gasket on the cap
and if there's only a small amount of oil don't worry about it.

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Mike F - 18 Jul 2005 13:29 GMT

> Dear NG:
> I replaced the cap, maybe the original, at 250k km and found it to be
> full of black powder and some oil. Shouldn't this part require a
> gasket or seal?
> TIA,
> H2Only

If your distributor is mounted on the rear of the head, oil can leak
down the distributor shaft and past the internal seal. The seal is not
available from Volvo (you buy a complete distributor for this problem)
but is available from aftermarket sources.

Signature

Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

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tony@somewhere.else - 21 Aug 2005 23:11 GMT

>> Dear NG:
>> I replaced the cap, maybe the original, at 250k km and found it to be
[quoted text clipped - 7 lines]
> available from Volvo (you buy a complete distributor for this problem)
> but is available from aftermarket sources.

Mike, my 940 Turbo has been bugging me for years with oil in the disti
causing hesitation. Will a new back plate with the seal and shaft in it
solve the problem completely? How much does it cost over there? Volvo
where quoting me GBP100s.

Signature

Tony

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Mike F - 22 Aug 2005 13:29 GMT

> Mike, my 940 Turbo has been bugging me for years with oil in the disti
> causing hesitation. Will a new back plate with the seal and shaft in it
[quoted text clipped - 3 lines]
> --
> Tony

It's just a standard type of oil seal, which can be had for a few bucks
if you can find it. The whole distributor is over CDN$400 from the
dealer, so GBP100 doesn't sound so bad.

Signature

Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

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