Cabin pressure

[jonbarrett]

When I pick up speed the pressure build-up in the cabin is excessive. It pushes the windows out of their seals and slows the incoming cold or hot air. If I lower one of the indows 1/2 inch everything is OK. On my other car the cabin pressure is vented through a panel hehind the rear bumper.

I guess the solution is to drill some large holes in the body, but where? I recall reading about a cabin vent modification but I'm not sure where.

I don't want to cause any other problems such as water leaks or incoming exhaust fumes. If anyone has a car with this modification I'd be very interested to hear how it was done.

[Extra 300 Driver]

jonbarrett said:

When I pick up speed the pressure build-up in the cabin is excessive. It pushes the windows out of their seals and slows the incoming cold or hot air. If I lower one of the indows 1/2 inch everything is OK. On my other car the cabin pressure is vented through a panel hehind the rear bumper.

I guess the solution is to drill some large holes in the body, but where? I recall reading about a cabin vent modification but I'm not sure where.

I don't want to cause any other problems such as water leaks or incoming exhaust fumes. If anyone has a car with this modification I'd be very interested to hear how it was done.

I would look for where the air pressure is coming in from, not let it out. If you do you will freez in the winter.

[Gazzab]

There was a mod applied where holes were drilled under the rear window. You dont want your rear window popping out !

[jonbarrett]

I'm assuming the pressure differential is the ram pressure of the air entering the ventilation system, even when the fans are off, plus the vacuum caused by the velocity of the outside air passing the body. Buy venting, the pressure would be equalised.

[Byker28i]

I thought the fans had vent's which opened/closed when you pressed the relevant buttons

[jonbarrett]

Exactly where does the fresh air enter the ventilation system and where are the hot and coldfans located?

[Olly]

What year is your car ?

Ours is a late '97 car & has vents below the rear window (if you curl your fingers under the rear window from the inside, you should be able to feel them - 2 long vents towards the middle of the window).

If the rear screen has been replaced at some point, the vents may have been blocked ?

[Byker28i]

jonbarrett said:

Exactly where does the fresh air enter the ventilation system and where are the hot and coldfans located?

One in each footwell. Sir needs part S of the workshop manual - Heating and ventilation
ftp://Anonymous:[e-mail]/worksh...

[jonbarrett]

Olly, my car is 97. I'll flex my fingers and see if I can locate them.

[jonbarrett]

Olly, well spotted, I shone a light under the carbon strip covering the lower window edge and there they were, two long slots straight into the cab. I can't see any point making them any bigger. Time to tackel the poorly filling door windws then. See new thread.