How to correct an exhaust leak???

[Mark Howard]

Hi - in process on my '75 1.8. I removed the heat exchangers, exhaust manifolds, heater boxes, etc. because the exchangers rattled, boxes were rusted shut and exhaust leaks were pouring from the copper gaskets b/t the heads and manifolds....So...

Took some exchangers from my parts car ('75 1.8 also, identical to my resto), cleaned and painted (hi heat paint) them and the manifolds, bought new copper gaskets, aligned and adhered the copper gaskets to the top of the manifold (I was very careful on this alignment) and replaced all on the car, careful to torque the nuts to 18 lbs (as per Haynes).

I cranked her up and .....same exhaust leaks from around the copper gaskets.

Any recommendations on how to fix??

[BenI]

2 ideas:

Did you clean up the heat exchanger ends with a file?

I found that when using the 'correct' copper stud nuts, that since they are soft they can catch on the flange and torquing correctly becomes difficult. I always install stainless washers.

PS-I dont know your technique, but I wrap scotch tape around the riser pipe ends on the heat exchanger to tape the gaskets in place. Of course you dont want tape on the meeting surfaces, but this really holds them in place.

[Pritchard]

I had similar problems with my exchangers. Exhaust leaks made the car sound like a lawnmower on steroids. I did as BenI suggests. Get a large file and file both tubes at the same time to get correctly aligned, flat surfaces for the copper gasket to seal against. This helped tremendously!

By the way, I used just a couple of drops of RTV to "glue" the copper gaskets in place while installing. I installed before the RTV set up so that the RTV would squeeze out and not interfere with the sealing surfaces.

Good luck!

Pritchard

[Mark Howard]

I did not use a file to clean the top of the manifolds, I actually sand blasted them. They were clean and smooth when mounted. I used a small amount of "high heat liquid gasket" just to glue the copper rings to the top of the pipe (only a little, not enough to squeeze out, just to adhere).

Could the bolts into the head not be tight enough? I was scared I would strip the aluminum threads in the heads.

Any thoughts?

[John Rogers]

You might want to make sure you are not running out of thread on the studs. Remove a nut that is easily visible and see how many threads continue into the mounting flange on the header. If it is close, use a washer or two. Good luck

[Bleyseng]

I think it's a combination of all three things here. I think you need to flat file the heat exchangers so they seat onto the copper gaskets properly. Try what John said, look to make sure you haven't run out of threads when you tighten the exhaust manifold studs. Lastly, tighten the nuts down to spec. This is done slowly so the manifolds seat into the heads right. It's a tight fit and you need to pull the exchangers evenly against the copper gaskets.They do bind against the heads giving you the impression that they are in. I even rap them with a rubber mallet to make sure they are in all the way. It makes a "solid" sound when they are in. Once they are seated, tighten to spec or very snug and no more leaks.
I like to fit the copper gaskets into the heads with copper rtv ( a small amount). That way I know they are fit into the heads just right. Then I install the exchangers after a quick flat file.
Geoff

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76 914 2.0L

[Bleyseng]

[QUOTE]Originally posted by Bleyseng:
[B]I think it's a combination of all three things here. I think you need to flat file the heat exchangers so they seat onto the copper gaskets properly. Try what John said, look to make sure you haven't run out of threads when you tighten the exhaust manifold studs. Lastly, tighten the nuts down to spec. This is done slowly so the manifolds seat into the heads right. It's a tight fit and you need to pull the exchangers evenly against the copper gaskets.They do bind against the heads giving you the impression that they are in. I even rap them with a rubber mallet to make sure they are in all the way. It makes a "solid" sound when they are in. Once they are seated, tighten to spec or very snug and no more leaks.
I like to fit the copper gaskets into the heads with copper rtv ( a small amount). That way I know they are fit into the heads just right. Then I install the exchangers after a quick flat file.
Geoff
PS I looked the torque spec's up, it's 15ftlbs.

[JP Noonan]

Make sure there aren't any old copper gaskets still in the head. I allways have to use a pick and a lot of muscle to get the old ones out.

Also if the HE leaked long enough it starts to errode the exhaust port surface itself. I have a set of heads from a PO with this problem so it does happen.

[HMeeder]

Noonan may have a point. I inadvertantly left the old copper seals in. They are a PITA to get out. I still need to replace the studs. Can't seem to get them to let loose of the heads. Project list gets longer by the day...

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Herb
'72 1.7 Tangerine 'Teen
'74 2.0 Red Rustmobile

[Lawrence914]

Hi Mark!

I had the same problem. Can you locate the exact leak? A good way to do this is to get a stethescope (minus the end thingie) and use the open hose to locate the leak (while the motor is running of course).

My problem was that while the exchangers were flat and copper gaskets new... when I tightened them up, it got just a little but cockeyed. Back the nuts off a little bit and try to reseat the exchanger.

Good luck,
Lawrence

[Lawrence914]

Try this:

Get a stethescope and get under the car and listen for exactly where the exhaust leak is coming from.

When you find it, back the nuts off a little bit, and reseat the heat exchanger in, tightening the nuts in a crosswise pattern.

I had the same problem, and it was due to the HE mounting a bit cockeyed, even though the nuts and gaskets were new, and the heat exchangers were flat.

-Lawrence

[3D914]

Mark,

I too had the same problem (I liked the lawn-mower bit-

I removed the heat exchangers to make my valve adjustment an easier job. What I found lead to removing the engine completely. The first thing I noticed was that several of the nuts were the incorrect type. Normally a 13mm hex (M10) self-locking nut is used. Some of these were just standard hex nuts! No wonder they came loose.

I also noticed it required separate sized sockets to remove the nuts. That's not totally unexpected, but then two of the inserts for the studs came out of the heads. Man, I hate it when that happens!

So down came the engine. I found in addition to the two loose inserts on one head, that some genius used - you're not gonna believe this - a stud with wood screw threads on one end, and M7 threads on the other.

At least I could now fully understand why my neighbor got all jerked off over the load noises coming out the back of my 914.

I hope your problem doesn't go that deep. If you know the work has been done by a competent mechanic you should do well with the other's advise. Good Luck.

Gerard

[SteveStromberg]

Here's the hot tip on exhaust nut's. Use the 911 barrel nut's they are the only way to go, they make the job of tightening the pipes a breeze. Steve

[Mike Kunz]

OK...reading all this great stuff, I now realize what other work I have to do! On my 2.0, the studs also pulled out instead of the nuts coming off....so I reinstalled the stud/nut assembly, torqued it and it sure does leak....so, my question, who supplies these studs and the aforementioned 911 nuts so that I do this right? (not a fun job!)

Thanks,

Mike

[SteveStromberg]

Try your local machine shop.I found that some Rabbit exhaust stud are the same as the Type4,They have a shoulder area and are very high strength. If the 911 barrel nuts cannot be found locally, PP has them part#311-129-777 . Steve

[SteveStromberg]

Try your local machine shop.I found that some Rabbit exhaust studs are the same as the Type4,They have a shoulder area and are very high strength. If the 911 barrel nuts cannot be found locally, PP has them part#311-129-777 . Steve

[Special K]

Steve,

I surfed around the PP catalog and found a "911 exhaust barrel nut" #K-085-011-02. Are these the nuts you're referring to? I see that they use a hex head for installation, that would definitely give you a lot better angle for torquing.

[SteveStromberg]

Those are the ones.The work great, No more trying to get a socket on the 12mm nut. One thing, you may need to install a extra washer to keep them from having the stud bottom out inside the nut, I use the thick 8mm washers.Steve

[SteveStromberg]

Those are the ones.The work great, No more trying to get a socket on the 12mm nut. One thing, you may need to install a extra washer to keep them from having the stud bottom out inside the nut, I use the thick 8mm washers.Steve

[Mike Kunz]

Should the studs be replaced if they are pulling out...any chance they might be stretched?

Where can I get the studs if they should be replaced?

Thanks!