advice on an exhaust leak

[twobone]

Hi,

 

I have a leak at the 4 branch header to collector connection that is up stream of my exhaust canister. The leak is on the bottom edge of the bottom tube. The system is stainless steel at that point on both sides of the connection

 

I'm thinking of trying the beer can shims with high temp silicone trick as described on blatchat.

 

If that fails, perhaps I can use some kind of circle clip can be used. Thankfully it would be hard to see

 

It think it is contributing to the backfiring.

 

Any other tricks of the trade?

[The Stig]

I have used Hi temp silicone many times for this and although it does dry out over time, is flexible enough and works.

 

Tried the been can trick too but sometimes causes even more leakage.

[twobone]

I'm hesitant to remove seperate the two sides for fear of making more leaks. Do I just try to squirt in silicone and then wipe off the excess?

[Croc]

Just to clarify - is this developing into a crack? If so does it makes sense to weld the crack?

 

I tried the temporary stuff on my old car and eventually ended up having to weld as the silicone stuff just cracked over time.

[twobone]

No I just think that the slip fit between the two joints is not tight enough or the prior sealant has gone off leading to a leak.

[MHKflyer52]

Hi,

 

I have a leak at the 4 branch header to collector connection that is up stream of my exhaust canister. The leak is on the bottom edge of the bottom tube. The system is stainless steel at that point on both sides of the connection

 

I'm thinking of trying the beer can shims with high temp silicone trick as described on blatchat.

 

If that fails, perhaps I can use some kind of circle clip can be used. Thankfully it would be hard to see

 

It think it is contributing to the backfiring.

 

Any other tricks of the trade?

 

twobone,

To the best of my knowledge the backfire your referencing in your post is most likely from the fuel being to rich and not burning in the combustion chamber to is fullest and should only occur when decelerating causing that popping sound at the end of the exhaust system. If it is backfiring through the intake then you have a timing issue or a valve that is not closing completely but that is just my belief and should be taken with a grain of salt.

As for the exhaust leak at the collector the joint is usually a slip fit with some type of high temp sealer that is flexible or has a seal ring inside that the exhaust manifold pipes push up against to make the seal, all of which will eventually erode from the flow of hot exhaust gasses through the system which is normal. A lot of collectors are welded to the manifold pipes to prevent exhaust gas leaks in the connection area for just that reason but that can make installing or removal for servicing difficult if not impossible. I personally would try some of this as it works very well and can take the heat.

http://www.permatex.com/products/Automotive/automotive_gasketing/gasket_sealants/auto_Permatex_Copper_Spray-A-Gasket_Hi-Temp_Adhesive_Sealant.htm

Hope this helps.

[scannon]

Have you tried a band clamp on the slip joint? I've had good luck using them. You can see it in the picture on the joint between the exhaust pipe and catalytic converter.

[twobone]

Great advice, thanks

 

I will try high temp sealant and then try to find a band clamp if that fails.

 

On the backfiring side, I've purchased some new idle and main jets as well as new mixture screws. I'm going to use the traditional caterham xflow Weber specs as the baseline.

 

My current idle jet is a 55F11. The more common spec is an 50F9. I'm hoping it contributes to curing my rough running.

 

I have a new Aldon distributor and a fairly new coil and wire set and my plugs are fairly new.

[gjd6640]

When you try the silicone don't get in a hurry and let it half dry and then go for a drive figuring that the heat will cure it. It won't and you'll end up redoing it. Let it cure cold for the recommended timeframe to save yourself the trouble of doing it twice.

 

I've used silicone with good results on a 4 to 1 slip-in collector that was a little gappy and leaking as a result. I disconnected the collector, pulled it off, cleaned the pipes to help it to stick, smeared a bead of silicone inside the collector and just a little on the outside of the pipe, pushed them together, and wiped off any that was still showing.

 

Minor exhaust backfiring can happen due to normal amounts of unburned fuel remaining in the exhaust if you have fresh air (oxygen) leaking in at the (very) hot end of the exhaust system so if that's what you're experiencing then sealing up the system will help. If the backfire is on the intake side then you'll want to track down the cause of that.

[slomove]

No I just think that the slip fit between the two joints is not tight enough or the prior sealant has gone off leading to a leak.

 

I have that with my exhaust since I got the car. The slip fit gap is just a bit loose and you could see soot blowout and I had backfire.

 

I tried squirting in the copper high temp silicone but turned out to be useless since it does not stick well to the soot covered and otherwise glazed surfaces. It blew out right away. Filling the entire gap was not an option for me since that would practically glue the two pieces together making disassembly very difficult (how would you get the headers off the engine?). I tried another few methods (e.g. a bandage from aluminum wire cloth covered with silicone) but all that did not last very long.

 

The system that I use now for a few years is a 2" wide wrap of corrugated stainless steel sheet. You can find it in the home improvement store with a rubber liner and hose clamps to repair and join sewer pipes (just discard the rubber because it will not stand the temperature and if too big cut to size to go around the exhaust joint). The rippled surface allow to conform with different diameter tubing. I lined the inside of the corrugated steel with copper silicone and some fiberglass cloth and tightened it to both sides of the joint with a hose clamp. They call it "no-hub-coupling"

http://s7.cdn.hardwareandtools.net/is/image/HardwareandTools/045734625341?wid=225&hei=225

 

This does not leak anymore, can be easily removed and lasted for over 5 years now. The silicone still degrades over time but can be easily re-coated.

 

Edited March 15, 2012 by slomove

[JohnK]

Slomove,

Nice approach!. Something I found that may work and live for a long time is refactory cement that's handled by Flexbar specifically, http://www.flexbar.com/shop/pc/High-Temperature-Adhesives-Cement-c82.htm which I used to cement my DEI exhaust wrap to my headers at both ends. Wurth also handles a pipe to collector sealer that's holding up so far on my car, It's at http://www.focussport.com/wurth.htm

Edited March 15, 2012 by JohnK

[twobone]

Thanks guys...some good options. I tried the silicone beer can shims last night. Will let it cure and then try it out.

 

I also found that the lead coil wire was not well seated into the distributor. Also one of my idle jets may have been blocked. We will see how she runs on saturday