So, I decided to replace my AC compressor yesterday. Unfortunately I had a couple snafus (broke a small plastic coolant line and found the supercharger idler pulley bearings are shot), and now my Jag is down while I wait for parts.

I have to drive my low mile weekend-toy E36 M3 convertible to work for now. Unfortunately, the rear window leaks, and it is supposed to rain everyday this week, ugh. I’ve had the car 5 years and it has only seen rain once or twice. I have to rig up a cover to stop water from getting through the zipper.

I’d like to put my new compressor back into the Jag and install the replacement coolant hose and serpentine belt, then drive without the supercharger belt installed. Will the car care? Will it run just like a low-compression NA car, or does the ECU have a intake pressure sensor that will get freaked out if it doesn’t see boost?

I only need to do this for a day or two, until this weekend tops. I can stay out of the gas and drive gingerly while I wait.

Thanks,

Mike

 

The supercharger will windmill by the vacuum of the intake, so will run to an extent.


As to if it can do more than start and move in and out of the workshop without the ECU having a hissy fit ???


I do know the old (1920s era) Mercedes GP cars could turn their superchargers on and off at will, depending on the requirements of power or fuel consumption, And so could Mad Max in his V8 Interceptor!


But they had one thing in common, NO computers on their cars.

 

No, I mean to work and back a few days.

I already started and drove the XJR out of the garage and parked on the street without either the serpentine belt or supercharger belt yesterday, so it will start and drive. I did get a “battery not charging” warning, but that’s to be expected with no alternator.

I’m wondering if it will be OK driving 60 mph.

On my Z32 300ZX you can bypass the turbos and the engine doesn’t care, you are just driving a lon-compression naturally aspirated car at that point. But, it’s from the early 90’s with far less computer and systems intermingled.

Mike

 

As I said previously, there is no mechanical reason for it not to work.... As for the ECU???


Personally I would rather put some duct tape around the leaky rear window of the Beemer and a towel inside, and use that!


It is relatively easy to dry out an interior... trying to sort out an ECU that has had a brain fart ?$?$?£?£?


Safest way... get a rental for the week.

 

Yes, unfortunately it is not a little water that comes in. The seams at the lower corners have come unglued, so all the water from the window is funneled through the zipper at those points. I had to drive it once before in the rain, and I had towels on the rear deck and they got soaked

I have tried re-sealing the window at the corners just now, we will see how it works. I do not have high hopes. I will put an opened trash bag and towels over the outside of the rear window for tomorrow. My wife has also suggested renting a car.

I suppose I could put the old supercharger belt back on for now. The idler pulley was making noise, and is obviously rough feeling and has play, but I suspect it will last a while longer, especially if I keep the revs down. I just hate to do the job twice.

Mike

 

I understand you can run it w/o the SC belt, but have not had a reason to try it.

If you do, when you re-fit the belt I'd do a hard reset (disconnect the battery, touch leads together) to reset the learned values. It'll run a bit rough as it relearns - you can help by following the process in the codes PDF. If you had codes, clear them too.

W/o the belt, if it doesn't throw any codes I'll be surprised! The PCM will (initially) find weird stuff at the O2 sensors for the apparent throttle opening. It should adjust fuel but I'd expect codes in the process. Probably reduced performance. Acceleration may be dire.

 

I drove mine around the block, without the belt, as I was trying to troubleshoot a rattle. It ran fine but was rather under-powered. It felt like I had lost half the horsepower. I wouldn't like to drive it much further than that.

 

I drove my XJR without SC belt like 2 months before having time to fix the pulley issue. no problem.

just making your XJR to XJ8

 

Great, thanks.