B951S

Not a major deal but its been pissing me off for a while. WHen the blower is on any setting (I usually keep it on 2 with the AC on in Texas) the volume (and sound) of air being delivered seems to change as I load up the motor. I am thinking some kind of vaccum related deal. When the car is idleing or pulling a good amount of vaccum, the blower seem to deliver fine. When the vaccum approaches ambient or positive boost the blower seem to get quite and lets up on the air. I think maybe a check valve is gone. Anyone have any idea??
Cheers

hosrom_951

The fuel vapor canister system has a vacuum valve that goes to one of the vacuum regulators on the blower. Opening the PET and watch the blower system you shall see what i mean. There is also a black horned shaped vacuum regulator for the blower. Clearly visible from the passenger side.

B951S

Mmmm. Thats strange, I thought the fuel vapour regulator and vaccum switch were independent of the blower circuits. The valve that regulates how much fuel vapour is let into the manifold is hooked up to the throttle body. The on/off vaccum device is hooked up to the inlet manifold via a thermo/temp vaccum switch. No connection right?

I am also aware of the accumulator near the battery. My bet is on the small blue check valve that feeds the accumulator. Thanks for the advice though..

tazman

The blue check valve is probably the problem or a leak in the lines after the check valve. Any chance you had the check valve out and might of put it in backwards?

hosrom_951

blue check valve next to the black vacuum controller right? There is no direct link between them. But i saw on the PET diagram that one of the fuel vapour system valves goes to the 'rabbit' ears valve under the intake. But then i saw a vacuum line going from the valves to another valve on the blower system. I could have been cross eyed that night, it was 2:00 am .

hosrom_951

Now i got a question. When the car is cold, or has been sitting for 20+mins. The blower in the center would not have much air coming out. There is noise coming from the blower motor itself, but very little air. However, the side vents have lots of air coming out. After driving it for 5~10mins, air starts to come out. Is this a vacuum problem? a valve as mentioned above?

B951S

Hosrom
I will have a look into it soon and report back. I never had the check valve out so I may have just died. Seems like this would only ever allow a vaccum into the accumulator which stores vaccum for the operation of the blower flaps I think. If it has gone the accumulator would never hold a vaccum charge. I will pull the manuals and look.

Are there many 951's in Dubai?? I was over there last year, saw lots of BMW 850's and Mercs.

Cheers

951Tom

B951S, my car used to do the exact same thing. My heater valve diaphram was leaking so the hvac circuit wouldn't hold a vacuum when under boost conditions. So I installed a new heater valve and I replaced the check valve because I found one for $3 at the local auto store in the section that sells all the HELP products.

hosrom_951

B951S: I will be waiting for what you found regarding the vacuum accumulator . No, there are roughly 3-5 951's in UAE. Some NA"s and a coiple of S's. LOADS of BMW"S, Mercs, 911's, Boxsters, Cayenns....

B951S

Tom
Now you really got my interest!
Can you tell me where the diaphram is located
Many Thanks

hosrom_951

NEWS FLASH B951S: Took a look at the vacuum acumulator. There is a vacuum hose coming out of it right? well i DO NOT have ANYTHING connected to it. Just the accumulator, and a vacuum hose coming from under it, cut, it measures roughly 2~3 inches long and goes nowhere. Now, i pin pointed the issue. But where does it go to?

951Tom

The diaphram is located on top of the heater valve. The valve is located between the firewall and the intake manifold...follow the heater hose and you'll find it.

B951S

Hosrom
I have just been poking around in there also. That accumulator should be connected to the vaccum take off line somewhere after the check valve. Basically the check valve ensure the heater circuits are always under a vaccum and the accumulator ties into the circuit to ensure there is always enough vaccum to operate the flaps.

Tom
I will check the heater valve diaphram, thanks. I just checked both of my recirculation vaccum units attached to either side of the blower. Sure enough one would not hold vaccum. Its a little better now but still not right. I bet my heater valve diaphram is leaking as well.

I just checked the manual, it says tests these by unhooking the line to the accumulator, connecting a mityvac, turning on ign and selecting recirculate and full heat then pulling a vaccum. The system should hold pressure and the recirp flaps and heater valve should all move. I guess thats what I should do then!

hosrom_951

I looked at the PET system, and it looks like the vacuum accumulator connects to a Y end going to the round thinga magij behind the brake booster. If you have a vacuum diagram for the blower system, it would be great. Since the previous owner removed ALL vacuum lines for the heater.