1985 745t

Title really says it all on this one. When I stop and pop the hood I can hear a hissing noise like air escaping through a small hole from the behind the head. I have attempted to figure this problem out but for the life of me have been left stumped.

Because of the position its really tough to narrow it down specifically. From the passenger side it sounds like it might be coming from over on teh driver's side of teh firewall (a la heater valve), but I JUST replaced the valve with a brand new one in perfect shape when I did the radiator. I've checked the hoses by the heater valve and all seems hunky dory.

From the driver's side it actually sounds like its coming from under the distributor, which I find really odd since the only leak that SHOULD happen back there would be a fluid leak. I've felt the crank sensor (name? under dist...) and the distributor itself and everything seems to check out. In fact, I would almost say it sounds like its coming up from the front of the tranny but I can't imagine what could cause the problem down there (rear main seal would just be a leak, not air... right?).

Recently I found that my crankcase cover was loose on the downside (more in the front with the screw by the CBV hand loose) but I tightened it down and the noise is still there.

Is it possible I blew out the crankcase gasket and am getting a tiny pressure leak from teh back of the cover in front of the distributor? If so I wouldn't be able to see it, but I've never removed the cover (had the indy do a tappet adjustment about a year ago) so I don't know what it looks like.

If anyone knows of a potential source for this I'd appreciate it. I should note that currently I only have two problems with the brick:

1. Clutch worn (slips under heavy boost at lower rpms in higher gears)
2. OD Oddities (OD spontaneously disengaging and failing to immediately disengage when actually turned off)

As far as I know neither one of these should be related to this problem. BTW, heater adjustment/climate control works fine and other gauges that rely on vacuum seem to work fine as well.

Thanks,
rt