Bob,
Thanks much for the comments.
As usual with this car, nothing is as it seems.
Here's some more surprises. The engine has about 6K miles on it.
Complete re-build. The only thing not done was to install hardened valve seats.
If there was too much pressure in the crankcase, then I would suspect
other gaskets would leak too (?) What do you think about this to check for too
much pressure - If I disconnect the valve (rocker) cover tube (remove the cap
I put on to seal) with the tappet cover still connected to the carbs, if the
crankcase pressure was high, there should be no measurable vacuum (measured
with a gauge) at the valve cover tube with the engine idling ?????? Any
thoughts ? I'm due for a valve adjustment, spark plug replacement, and wires &
cap replacement - I'll do the compression test at the same time.
Unfortunately, having owned five Alfas and two Toyota Supras (7M), I'm very
familiar with leaky head gasket symptoms :-) So far, none have surfaced and
car has good power. One thing I cannot seem to cure is a chronic high idle
problem - I keep fixing it and a few hundred miles later it comes back (?)
Seems like a vacuum leak, but I just can't find it.
I've never tried opening the tappet cover with the valve cover still
plugged. I've tried opening the valve cover with the tappet cover still
connected to the carbs and opening both to atmosphere - both produce the leak.
I was originally going to leave the tappet cover connected to the carbs and
open the valve cover tube (and install an small air filter on the valve cover
tube), but the high idle problem (and the leak) precluded doing this.
Someone else just E-Mailed me about a single piece cover that he used
to finally cure his leak. What I'm actively looking for is a cover from an
older car that has a gasket channel. On my car, the rear cover (with the
gasket channel) hasn't leaked a drop !!!
Thanks Again For The Time, Skip
P.S. 250M miles for mains. That's impressive. I can't imagine 150K for any
MGB engine. What's the record out there for an MGB engine without the head
being removed ????
-----Original Message-----
From: Bob Howard [mailto:mgbob@juno.com]
Sent: Wednesday, March 10, 2004 10:43
To: Christian, Wellner L. CIV COMNAVAIRSYSCOMPATUXENTRIVERMD AIR 4.1.1.4
Subject: Re: Desperate - Oil Leak From Front Tappet Cover
Hi Skip,
You have been pretty thorough with this.
When you connected tappet cover pipe to the carbs AND blocked the
valve cover inlet, the leak stopped. That confirms that the carbs are
pulling vacuum.
Then, when you open anything (assume that you refer only to opening
rocker cover vent tube) it the tappet cover leaks. Hmmm.
That might be telling us that there is more pressure in the block than
the vent system can handle---I suspect that if this is true the gasket
leaking is a symptom, not a problem in itself. Let us hope I'm
wrong.....
Another test---when engine is running and the thing is leaking, is
there pressure coming -out- the rocker cover pipe? If there is,
that's confirming pressure inside the engine instead of the vacuum
(depressed pressure) that we want it to have.
Put your compression tester on each cylinder and get readings. What I
am wondering is that there might be a broken ring that's allowing
combustion pressure to get past the rings and into the block, and that
this large amount of hot air/gas/pressure is overpowering the suction of
the carbs. If that's the case, you have to drop the sump to undo
connecting rod bolts, pull piston out the top, check for cylinder wall
scratches, replace the rings, etc. BTW, whenever you have the bottom off
the engine, replace connecting rod bearings. They are cheap and easy to
do, they last 65-70M miles, and if you keep them good the oil pressure is
good, and the main bearings, dificult to replace, will last upwards of
250M miles.
I don't know of another cover available, but the cheap 18V cover will
work OK under normal circumstances. If it's straight, not warped, and
the block surface is clean, it will not leak (assuming there is no
pressure behind it). Someone suggested that you stick the gasket to the
tappet cover, let it dry for a day, then fasten to block. Yep, that's
the right way. You --should-- be able to do it all at one time, but doing
at one time has not worked for me either. Actually, you --should-- be
able to use gasket goo on the cover, stick on the gasket, then not
use goo on the block. That allows you to remove cover and to re-seal
again using same gasket.
Look for pressure loose in the engine. ---any signs of oil in the
coolant, or water in the oil? Oil sheen on the antifreeze or light-tan
creamy stuff on the dipstick or filler cap? Does the vent tube from the
tappet cover smell of combustion or just smell of engine oil?
A small-plane pilot friend gave me this handy tip----keep cheap paint
thinner in a squirt bottle. Use it to clean engines when chasing leaks.
It's cheap, not particularly flammable, dries fast and doesn't leave a
sheen (unlike kerosine) when wiped off with a cloth. I've found more
leaks that way, and fixed most of them.
Bob
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