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914World.com _ 914World Garage _ Exhaust leak

Posted by: solex May 27 2007, 01:58 PM

I have been searching for my exhaust leak and cannot find it and need some help.

It started last fall, when I came to a stop I heard the exhaust leak (it was quite loud).

I remove what I thought was the offending heat exchanger and noticed a pulled out stud, I replaced it with a timesert and have remove and installed the exchanger at least 4 other times now unable to fix what I thought was the source of the leak.

In the process another stud pulled out and I replaced it. I have installed new copper gaskets (annealing them before installation) and made sure the tops of the heat exchanger are level with one another.

I had installed these heat exchangers earlier last year with out a problem.

Help... where should I look next?

Posted by: Headrage May 27 2007, 02:11 PM

When you checked them to make sure they were even, how did you do it? Straight edge or eyeball?

I would still use a big file and make sure. Also, you might want to file the ears down a little as well. As you take material from the ends of the exchangers it moves the ears closer to the head.

I had a similar problem and found that the ears were hitting the head and wouldn't allow the exchanger to seat properly.

Posted by: Cap'n Krusty May 27 2007, 02:48 PM

Is it a loud popping sound, louder when you give the throttle a quick blip? If so, look for a head leak. The Cap'n

Posted by: sendjonathanmail May 27 2007, 03:00 PM

throw some carb cleaner down there while the cars running...where you see flames is where the leak is :D just kidding...dont do this...--JON

Posted by: Bartlett 914 May 28 2007, 09:55 AM

Headrage may be correct about the ears on the HE's.

I read somewhere about doing a leakdown test from where the muffler attaches. Make an adapter to stick in the end of the HE for applying compressed air. You need to make sure the exhaust valve is closed. Apply some compressed air to each port one at a time. I don't remember how much pressure. I would guess 10 to 20 lbs. Watch the pressure to see if it drops. If is does this quickly, then there is a leak. I will be changing to a freshly sealed motor soon and this is what I plan to do.

Posted by: Paul Illick May 28 2007, 10:14 AM

Get a short length of heater hose, get the car up in the air with the engine running, stick one end of the hose in your ear and begin listening around If you really got after the exhaust/HE's then I suspect the Cap'n is right and it's a cylinder head leak. Don't put off fixing it.

Posted by: r_towle May 28 2007, 10:48 AM

If I can add any value, this is what I have found.

Take off the muffler, and loosen all the HE's
Look closely with a light or remove the HE all the way to examine how the mounting tabs look where they are welded to the HE.
This is a weak spot that can tear, and create a leak.
Then if all is well, hand the HE's on the heads, loose.
Hang them on the rear muffle support bracket, no muffler.

Tighten the HE down in a cross pattern, to bring it to the head both pipes at the same time, be patient, do a little at a time.

Then torque it up, both sides.
then hang the muffler, but keep the weight on you until all the bolts are tight and the hanger bolt is doing the work.

Now, start and listen.
If you still have a leak, use the long vacuum line as suggested above to listen exactly around each connection.
You will hear the area as you get close, then move the hose end around and hunt for the noise...
It really does work perfect using a hose in your ear.

Good luck.
Rich

Posted by: solex May 28 2007, 12:42 PM

There was a slight bottoming out of the tabs, I added an extra set of gaskets to compensate and it did not solve the leak problem.

I guess it is as the cap'n stated. I hear a loud popping/slapping sound and it gets louder when I give it the gas, although I cannot see the leak it appears to be coming from the number 4 cylinder.

Oh well a top-end rebuild (while she is out)???

Posted by: Jake Raby May 28 2007, 07:41 PM

A head leak has a distinctful sound much different from an exhaust leak... I bet the Cap'n is right on this one...

OR you could have blown a chunk out of the combustion chamber right above one of the exhaust studs... That happens when people redrill exhaust studs too deep of flycut heads too far..

The easiest way to find an exhaust or combustion leak is by climbing under the car and having a friend dump some automatic tranny fluid down the intake at around 3,000b RPM carefully... You'll smoke up the entire neighborhood but you'll illustrate EVERY exhaust or combustion leak the engine has!

Posted by: solex Jun 23 2007, 11:00 AM

I just checked the compression in each cylinder, #4 -130 PSI, #3-120 PSI. Not sure where the leak is coming from and I cannot do the tranny fluid in my area.

Posted by: rhodyguy Jun 23 2007, 12:51 PM

righto on leaving the muffler off. before you get to the x torqueing sequence, try pushing up on the he, and run all the nuts on until just off contact with the ears. the he will be slightly lose. now push up again and try to rock the he, you'll know when all 4 pipes are in contact. start the torqueing in stages. if you should run a nut on to full value it's possible to put the he in a bind and it may never completely seal no matter how much you reef down on the remaining nuts. then the studs start spinning in their holes or break. have you tried sticking the sole of you shoe on the exhaust pipe while the engine is running? that can help locate what may be the offending exhaust port.

k

Posted by: solex Jul 12 2007, 07:25 PM

Broke down today and brought the car to the mechanic. Turns out that the exhaust leak was not from the heat exchanger but it appears to be from the ports on top of the heads for the air pump. The mechanic said that one of the tubes is loose in the head. Also the engine now starts but will not run....

When it rains it pours and I really wanted to drive it this weekend.

Any ideas to fix the exhaust tube with the engine in the car?