Exhaust gas return pipe (?) crack---patch or replace?

[BDB]

So I've had this annoying rattle at around 2000 rpm, regardless of acceleration or deceleration. so finally i had some time tonight to inspect. first, one of the heat shield holes enlarged and broke off so i had to weld a metal washer so that the bolt can secure the heat shield down on that side. so hopefully that fixed the problem. i'll find out tomorrow morning on my drive to work.

the other thing I found was that the exhaust gas return pipe (i believe that this is what it is) had a crack at the end of the exhaust manifold. see the attached pic. both welded points had cracked off so i welded one broken point back on (near the holes).

also at the end of the manifold, there is a hole too. I took a screwdriver and inserted in. its a hole.

so my questions:

- what would cause these holes?

- the space is too tight to weld on the pipe part. have any of you guys used some sort of patch product for something like this?

- as for the hole on the exhaust manifold. I could spot weld it over and cover the seams with the right kind of permatex.

- now could these holes in the return pipe and the exhaust manifold be the reason for my atrocious gas mileage? i would guesstimate that my mpg on my last tank was 12-13 mpg. mostly short drives to work (3 miles each way) with some mixed highway drives.

thanks for any and all help,

bob

[tlapham]

The old metal deteriorates after 30 years of vibration and expanding/contracting. It can definitely degrade your mileage, but 12 is pretty bad... What year is your car? if you don't have to worry about smog, just remove all that crap and get a performance header. Otherwise, i have the entire system from a 78' 320i in perfect shape...

[BDB]

The old metal deteriorates after 30 years of vibration and expanding/contracting. It can definitely degrade your mileage, but 12 is pretty bad... What year is your car? if you don't have to worry about smog, just remove all that crap and get a performance header. Otherwise, i have the entire system from a 78' 320i in perfect shape...

i figured fatigue and age would be an answer it just seems coincidental that it woudl be happening at the butt end of the exhaust manifold.

yeah, 12 is bad. i really am surprised by it.

i have a 76 and i live in CA. i have to keep the crap on.

what system do you have from your 320i?

[schwartzerritter]

Oh bloodly hell.

good luck

[BDB]

Oh bloodly hell.

good luck

schwartz,

haha, thanks for the words of encouragement.

im going to look into exhaust repair kits (tyipcally used for mufflers). we'll see how that goes.

like you (and i) see, its not an easy repair. i tack welded the broken joint there last night and there's no way i could ever do any sort of precision welding in that area.

[BDB]

today I patched the hole in the exhaust manifold chamber. luckily there was enough room to make some spot welds and build n' fill from there. i bought some kind of high temp metal filler to seal up any pin holes. seems to have solidified well.

As for the hole in the tube, whoa what a challenge. i could spot weld and fill the holes the same way, but it would probably cause a lot of turbulence. I've bought some sheet metal and will form fit a patch over it. I'm gonna try to cut the hole a nice retangular shape so i can cut a patch to fit in. spot weld as many places as possible and then fill w/ the metal filler.

i can tell already that patching the manifold hole made a difference. it seems to pull smoother than before. at least thats what my ass is telling me.

[BDB]

Update:

Seems that the cement/patch material has crumbled off and the engine again sounds like an air cooled VW from that side of the 02. I believe the best course of action will be to cut off the pipe, weld the hole up, and then reweld the whole shebang back onto the exhaust manifold.

Rattle was from three different sources:

- heat shield over the manifold had a hole that prevented the bolt from being secured. Also, the one of the mounts underneath the heat shield was missing so i fab'd and welded one on

- egr pipe was busted off (see pic above)

- biggest rattle was the U-bolt that was held to the transmount was busted. it was a J-bolt

[Guest Anonymous]

get a mapp gas/oxygen brazing kit. I've repaired the exhaust manifold reactor on a '76 with this method. The iron, sheetmetal, and tubing metal flows when it is cleaned and fluxed properly. In CA you gotta keep the parts working or else......every two years you'll be in a bind. Since cleaning the metal is key, you may have remove the manifold and tubing. Major PITA GL.

[BDB]

geezer,

Thanks for the advice. Yes, I believe I will need to remove the manifold. I am also welding more mounts on that return pipe at each end (vibration has broken both as you can see)