Does anyone know what the diff side of the rear muffler mounts to? There is nothing near the hanger. There are body holes and I have some temporary wire there. Realoem lists a rubber hanger but doesn't show what it hangs on to, but also shows the mount horizontal, this one is vertical.
It looks like the rear diff mount was replaced and possibly re-welded at some point, all of the underbody coating has been removed around it, and maybe the hanger was lost at this time. The exhaust had some really half-assed work done at some point and I can't tell how things originally went. The 'transmission mount' was just a bent piece of metal sitting on the side of the tranny welded to the pipe. The rear mount is a bizarre custom mess.
Exhaust is basically only supported at the rear and the manifold which isn't great. Wobbling in the middle is just asking for cracks.
Also, the gas tank gets so hot from the exhaust that it bubbles and burbles for a while. Is this normal?
I can't really tell from your pic, but it looks like something's missing. There should be a corresponding part on the body similar to the square hook on the muffler. It might be rounded on the body, on the muffler there is a plastic insert along with the flat circle with a band in the middle rubber mount. Unlike the overgrown rubber bands in back, even carrying most of the weight, the front mount lasts a long time. The obvious guess is it disappeared with the diff mount repair.
Searching the memory banks here, it seems like I had problems with it on some car I had, probably the 79 E12. Details are beyond fuzzy, I think I had to do a repair which was pretty much verifying clearance, drilling a hole and using a bolt with a couple of large washers. But I still had the bracket, it was just tearing loose.
You really want to do something or else the rubber bands at the back will have a very short lifespan and maybe have you dragging it sometime.
Thanks Mike, I'll see if I can just drill and install a bolt. But as for your second point, it looks like some exhaust guy noticed the same thing you did and came up with their own solution. It's a 90* rod that slots into this custom rubber mount, and feels really solid, it's well and truly locked in place. I just worry about the center muffler bouncing around and causing cracks. I guess with this tough rear mount, it's not so crucial to get the rear muffler diff mount replaced?
Interesting, I've never seen anything quite like that. How's the noise and vibration from the exhaust? It's rubber, but a lot more solid than the rubber bands that are original. Some sort of a forward support would still be a good idea as heavy and long as the system is, but that does look a lot beefier than stock.
Mike W.
1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter
The car is definitely louder than today's cars which are virtually silent when idling, but I don't know if that's just because cars were louder 40 years ago. There's no excessive exhaust vibration or noises that I can hear, but I don't have a reference. This setup does makes it really easy for one person to remove/install the exhaust, just hook it in and the whole thing is supported rather than holding it and trying to get those stupid rubber doughnuts on. Just the rod is welded to the tailpipe, not the muffler itself so that is a potential weak point. I will look into the additional support for the rear because taking the load off is a good idea.
Happy for you to see it in person and tell me how loud it is. The Bay Area E12 owners should crash a GG BMW CCA cars and coffee. But probably not in summer because our AC, if present, likely doesn't work too well.
I looked at the original exhaust on my 79 and can verify the mount /hanging points - 2 rubber donuts at the rear of the exhaust by the tailpipes, on the same muffler a rubber piece that looks like 2 "E"'s put together that supports the muffler to a mount on the body, then all the way forward to where the down pipe connects to the cat is a solid mount to the crossmember. That's it, 3 points for the entire exhaust.
Looks like you're missing the body mount for the front of the rear muffler. And yes, that muffler will get hot but not so hot as to boil the gas in the tank!
79 528i
76 530i - Stored since 1992, can it be brought back to life?
86 944- 2023 project
78 F150- Everyone needs a truck
I don't have those pieces, so wondering if that's a part of it.
Also I've discovered a pinhole leak/seep on the gas tank, which I guess is contributing to the 'boiling' noise it makes - it might actually be sucking air in as it's cooling down and making a similar noise to boiling water. It's strange to me how close the hot muffler is to the gas tank, but I guess (hope) they knew what they were doing!
PatinaBeforePolish wrote:I looked at the original exhaust on my 79 and can verify the mount /hanging points - 2 rubber donuts at the rear of the exhaust by the tailpipes, on the same muffler a rubber piece that looks like 2 "E"'s put together that supports the muffler to a mount on the body, then all the way forward to where the down pipe connects to the cat is a solid mount to the crossmember. That's it, 3 points for the entire exhaust.
Looks like you're missing the body mount for the front of the rear muffler. And yes, that muffler will get hot but not so hot as to boil the gas in the tank!
