I got this 65 mustang with a 200 in it. She runs great. Starts up right as you turn the key, and this is 2 years after just sitting in the garage. But there is one problem. I have an exhaust leak, not just some minor noise or leak you can hear, but a loud air blows from the 6th cylinder, it also seems like it is coming from the lower bolt, but I am not sure. You put your hand back there and you can really feel the leak, puffing against your hand. So I thought it was the gasket. Replaced it. No success. So I decided to get my exhaust manifold milled flat. No success. So I took it off one final time and really gooped on the ultra copper gasket sealer with the gasket. No success. And this last time I looked around for cracks, but it looks all good, also the head "seems" flat. I say "seems" because I have limited time and resources, and I left the head on I just tried looking around from that angle. So I am wondering what are some of your thoughts? Is it the head? Is it the manifold. What do I do to get this problem fixed?
Exhaust Leak I just cant figure out
- Thread starter pookster
- Start date
mysavioreigns
Famous Member
Do you have all the mounting bolts in there? I forget the exact number. I would say you're missing one, but it sounds too big of a problem to be just 1.
...Maybe you've got a crack in the head?
...Maybe you've got a crack in the head?
MercuryMarc
Well-known member
Have you tried to find the noise using a 3 foot length of hose with one end to your ear and the other moved the around the engine until you find the leak? Worked better for me for vacuum and exhaust leaks.
Yep. I had an even more insidious one: the head gasket was blown out at #4. The air blew right on the back of the manifold and down the downpipe, and I thought it was the donut gasket for the longest time. I must have had that thing off a hundred times, filing away at the donut or putting sealer or new manifold gaskets on. Couldn't ever find soot on the manifold gasket, that's the giveaway.
The car ran fine, didn't skip or anything. It had so little power anyways that I didn't notice one cylinder venting to atmosphere!
The car ran fine, didn't skip or anything. It had so little power anyways that I didn't notice one cylinder venting to atmosphere!
Sounds like you guys are describing exactly what I am hearing. It is very loud with a lot of air flow. So it looks like I am going to have to pull off my head and replace the head gasket. After I do a compression test. BTW what should the compression be and would the leak make it a huge drop in compression? or just a couple of pounds?
You'll notice a compression loss by the significant difference that one or two cylinders show, compared to the rest.
For most of the motor, I'd expect consistent results (within 10-15 pounds of each other) in the range of 110-180 PSI. That overall range is large because of the great possibilities for original compression ratio.
Regards, Adam.
For most of the motor, I'd expect consistent results (within 10-15 pounds of each other) in the range of 110-180 PSI. That overall range is large because of the great possibilities for original compression ratio.
Regards, Adam.
