Exhaust leak question

taylorcom

taylorcom

Well-Known Member
Messages
273
Reaction score
32
Location
SF Bay Area
I noticed an exhaust smell inside my '70 2800 CS and took a look underneath. With my fingers I could feel definite leakage where the 2 small pipes coming from the engine connect to the 2 small pipes that head to the back of the car. (I think this area is more or less under the front seats of the vehicle.)

I tightened the 6 bolts that hold the 2 gaskets in place, but am not sure I improved things much. And without a lift, it's a hard place to reach.

Does anyone have any ideas on this? At this point I'm not sure if I need to replace the 2 gaskets, the pipes, or both.
 
I would get new gaskets and:

You are going to have to raise the car up and pull the whole exhaust off (including the downpipes). Pull the two pipes apart and check the metal condition. You may be able to get away with sanding the rust on the outside of the downpipes and on the inside of the pipes leading to the center muffler. My downpipes ends were so pitted that I cut them off and welded on new sections of pipe for a better seal. If the center resonator is shot, or about to go, then you should replace that as well.

good luck,
 

Attachments

  • TwoPipes.jpg
    TwoPipes.jpg
    75.4 KB · Views: 144
The donut gaskets that go there are stiff themselves and don't offer much of a seal unless they fit very well. Make sure the flared end of the center resonator is even; see to it that the two ends of the header are in fact round (gaskets likely won't fit on at all otherwise).

There ought to be something deformable and heat resistant that will provide a better seal, other than taking out the gaskets and welding the resonator to the headers, but that is an option.

My backyard approach might be to see if I could wrap the stub pipe ends with a layer or two of fiberglass, the better to seal the pipes, but this isn't much of a recommendation.
 
There is a metal ring that fits within the flared end that the two rings then lock together. I have seen these wear away to almost nothing.
 
Honolulu -

As for sealants that might be used on the inner pipe's surface, I'd think muffler cement (that grey stuff u buy in a tube at the local auto-parts store) could work. It's pretty tough stuff.

Also, I hate to admit it, but I've used DAP Kwik Seal Plus Kitchen and Bath Adhesive Caulk to plug an e9 muffler problem. Specifically, at the back end of the muffler, where the tailpipe attaches, there was/is leakage from the seams where the muffler's flat, oval end piece is welded to the muffler's body shell. DAP Kwik Seal sealed it, tho it needs renewal every now and then.

(DAP Kwik Seal also works well as a general-purpose glue, but gets terrible reviews for its intended purpose: http://www.homedepot.com/p/DAP-Kwik...-Adhesive-Caulk-with-Microban-18864/100172358).

Cheers.
 
It's been a while, but today I jacked up the CS, slid underneath, and removed the 6 bolts that hold the leaky exhaust joint together. I was able to slide things around a bit (w/o removing the muffler, etc.) & looked for corrosion. I didn't find anything that looked like a serious problem.

The pipe-end that slips inside the bigger pipe-end doesn't look corroded. It looks basically ok. So do the 2 donut gaskets: while there is some wear around their outer edges, their inner surfaces (that are supposed to make the seal) look smooth.

I'm thinking of applying some muffler cement, reconnecting everything & hoping for a good seal.

Does anyone have any ideas on that plan? Also, can anyone recommend a good muffler cement?

Many thanks.
 
Just about anything really viscous ought to work if that's your decision path. It would help if it's heat resistant as well.

You can thicken various glues with bits of fiberglass, cut at an angle to the weave, so that the cuttings are short lengths of fiber. But you want more than a glue, you want something that can act in bulk whereas glues typically work as thin sheets between two closely fitting materials.
 
It's been 3K miles since I put in new donuts when I did my motor and one them was very loose, horrible leak. Tightened as best I could but I need to get it on a lift. These donuts wear out, my old ones were paper thin.
 
Hi Taylor, exhaust smell can really ruin your drive so I would take it seriously for many reasons, not only your health-and your passengers' but also for the areas around the leak that may get affected by the high heat. For that reason I don't think it's unreasonable to locate a muffler shop in the area, you can drive around and try to find someone who is interested in classics and ask them when a good time might be to bring your car in and have them look at it and make the repairs permanently. Yes, it is not as satisfying as doing the work yourself but it may end up being just a little more than doing it yourself. I have a local shop where I hang around outside the bay while they work on the exhaust and they show me what they're doing and kind of check through the process as they move along. My guy welded flanges on the pipe ends where the donuts go and put proper gaskets in there which is allot easier than fitting in the donuts and makes dis assembly a snap. It's always good to know people in that line of work and allot of welders in those shops have their own classics so they are usually excited to work on an e9.
 
Peter,

Thanks. That's an interesting modification you describe. As is, the joint is not easy to work on w/o a lift, but I found that jacking up the car at the front driver's side jack point (& then supporting it with a proper jack stand or 2) allows access. Then it's a matter of sliding underneath & wrestling w/ wrenches.

I agree that exhaust leaks must be taken seriously & dealt w/ effectively, for both pleasure and health reasons.

-- Steve
 
Last edited:
HB Chris said:
There is a metal ring that fits within the flared end that the two rings then lock together. I have seen these wear away to almost nothing.
Click to expand...

This is a puzzle for me and maybe someone can explain the logic: One ring is solid metal and the other is a deformable heat//fireproof material. PN 18119067822 is the deformable one and looks like this --soft metal ring with material that looks like asbestos but isn't:
images


or like this --no metal and totally made up of that asbestosy-looking material:
18119067822.jpg


The other one is PN 18111245960 and is a solid metal ring with a slight ridge around it like so:

551492_x800.jpg
 
Luis,

Not sure I know the logic, but the rings on my e9's exhaust are like the last one pictured in your post: PN 18111245960. I think that even tho it's all metal, the ring is supposed to compress a bit to make a tight fit.

There are small rings at the joint I'm now working on, and a bigger ring connecting the tail pipe to the muffler.

These donut rings taper towards their outer edges.
 
The ones that are all metal are not compressible at all; they are solid. The compressible ones after being in there for a while look like they are solid (rotten/rusty)metal but are really that other material that's been compressed. :???:
 
I've been successful using the 'red' RTV silicone which is designed for higher temps on the exhaust pipe connections after the cats on my Porsche 928 GTS. That car was not operated at max RPM very often. When I did the same on my track car - Porsche 928 S4, where the max revs were reached about 6 times every 2 1/2 minutes, with RPMS rarely below 3.5K, the RTV would last for a few days, but not a season (12-15 days of tracking).

So, you might try that approach with your street/highway car.
 
You must log in or register to reply here.
Back
Top