I just bought a '89 951 (former Boxster owner) to use as a daily driver and a track car. The air coming through the vents is much warmer than the outside air, and the side vents are even warmer. Sometimes the air from the side vents is warm even when the AC is on. If I turn the temp **** up, it will get much hotter. It appears that the heater will not go completely off. Is this a vacuum issue? Also I was wanting some opinions on what the best spark plugs for this car would be. Thanks!

 

Best spark plug is a copper NGK or bosch. Do not run bosch platinum 4's in the car. The heating issue sounds like a disconnected vacuum line from the heater control valve, either at the valve itself or at the firewall.

 

Thanks! I intend to learn as much as I can about this car. Why do you say not to use the platinum 4's? Are the 2's ok? On the heating problem, why do the side and floor vents run hotter than the center and defrost vents? Also, this car doesn't stop near as quickly as my standard Boxster did. I'm going to bleed the brakes and put on some good brake pads. Do you have any other ideas? Thanks!

 

The center platinum tends to erode away and fall out and they run a little hotter. Even if there are 4 tips on the plug, the spark still only comes from one of them. Not sure on the heat, do you have hot air all the time, or is this just when the temp **** is turned to hot? There is also a clip that tends to break underneath the dash, that can cause a heat condition....i will see if i can find a picture of where it is located. For the brakes, start with the pads and a flush, but make sure you check the condition of the rotors as well. Are you gettting a stiff pedal when braking? If not, i would check the vacuum at the brake booster.

 

I get warm air from the side and floor vents, even if the AC is on. The air will go from warm to hot if I turn the temp **** to hot. Even though I don’t touch the controls, it fluctuates slightly while I’m driving from warmer to cooler and back. If the AC is off none of the vents will blow air as cold as the outside air.
As for the brakes, the pedal feels fine to me, it is definitely not a soft pedal.
So is it bad to use any platinum spark plug?

 

The spark plug debate has been beat to death over on rennlist, the vast majority will say use a stock copper plug, either an NGK or a bosch. I dont remember off hand what the numbers are exactly for part #. Stay away from platinum in these cars. Did you check the vacuum line at the heater control valve (between the firewall and the engine), it sounds like you are having a full heat condition even when the AC is on, so i would check all your vacuum lines there and the 2 connections at the firewall first.

 

It is definitely not full heat, because if I turn the temp **** up, it gets much hotter. However, it seems that the heat won’t completely shut off. I will check the vacuum lines tomorrow (I had to work this weekend). What is the best way to check the vacuum lines and are they easy to find. I assume I can follow a coolant hose to the heater control valve, and follow the vacuum lines from there. Thank you for all of your help!!

 

Its either the vacuum line to the heater control valve or the valve itself is failing and needs to be replaced. As for the spark plugs, in addition to what Karl said (and Karl is right, bt the way), the platinum creates "hot spots" that will cause detonation which in turn can lead to blown head gaskets, holes in pistons and a whole bunch of other problems you don't want. No "platinum" plug is safe to run in a 951, if you don't believe me I will get you the number to at least two guys I know that lost their engines for this reason, they'll be happy to tell you all about it. Bosch copper is the way to go in a 951, in my opinion.

Your brakes on the 89 951S should better than a stock Boxster, and only give up a slight margin to a Boxster with Big Reds. Start with fresh fluid and decent pads (Perf Friction makes good ones for your car) and see if that doesn't make the difference. Also, stay away from drilled/slotted rotors, the stock OEM rotors will do everything you need to do, including hard core track situations.

Regards,

 

For what its worth im a new porsche owner also & had that warm air issue on my 91 944 S2. I had to take it to mechanic since i wasnt sure what was wrong w/it & the A/C needed looked at/converted. my problem was just the clip that was mentioned in above message, i think the gold rod that comes down under the dash is called the heat actuator rod (not for sure on that) but at any rate yes there is small plastic clip that the rod sits into. I went to my local porsche shop & picked up a new clip for $2 i believe it was & fixed the problem w/warm air etc.. course my A/C had to be converted over to the R-134a also before it would work. O btw that small rod under the dash is on the drivers side & youll have to crawl under there & take off the plastic cover to see/get to it.

hope that helps a lil bit.

storkman

[IMG]local://upfiles/1361/BA622573EAAA42BBB4330A4E5404E27B.jpg[/IMG]