Type IV Engine ('72-'79 Bus) Exhaust Leak
by Steve Dolan and David Schwarze
I think i have finally found out what the ticking noise is on the '73 Westy...Exhaust!!! #2 to exhaust port to heaterbox joint. I removed the muffler and R/H heater box today and found the brass crush gasket black and sooty about 1/3 the diameter as well as the adjacent head area. I checked the pipe for squareness and filed it smooth and reinstalled all the exhaust and the noise is still there!
Steve Dolan responds:
This is a constant problem with the '76-78 exhaust system. The ports need to be square to the bolt holes in both planes (side-to-side and front-to back) and in a common plane with each other. The ends are attached to the manifold pipes on the '76-78 by two puny tack welds and I think over time they warp or move. At any rate, the manifold gets very difficult to get on and off and stops sealing :-( The easy solution is to take the box to a machinist or you can:
- Get two rods the proper diameter to fit the holes in the heater box end;
- Insert rods and measure that they are parallel (they probably won't be) and the same distance apart as the studs in the head (again, probably not).
- Take the header/box and lay it on the face of the exhaust ports on a formica counter.
- Try to rock it up on either port;
- Move it to the edge so that one and then the other port hangs over the edge while the other port is flat to the formica. See if it drops down.
While a formica counter is not the same as a machinists surface block, it is *very* close! There are few items in common use as flat as a good condition formica countertop! If any of the tests above revealed an out-of-trueness in you pipe ends, then that needs to be corrected or you will have leaks.
Note also that there is little margin for error, if you grind too much off the end, then the shoulder of the bolt flange will meet the head before the pipe end meets the copper gasket. In this case, you can grind a bit off that shoulder. *both sides*! *evenly*!
David Schwarze responds:
This bus wouldn't happen to have the Dansk heat exchangers on it, would it? The ones I got from VWOA last year wouldn't seat on the port, but bottomed out on the stud bosses, and thus wouldn't seal. The mechanic at the VW dealer attempted to solve the problem by overtorquing the studs, and ended up pulling one clean out of the head. When I removed the stud, the aluminum threads were still attached to the stud and came off like a helicoil. The mechanic gave the bus back to me and told me, "It had that exhaust leak when you brought it in." Grrrr...but I digress. My solution was to get out the cutoff tool and remove about 1/2cm of the flange where the stud goes through so it could push the heat exchanger farther up towards the head. It has sealed fine ever since.
