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Old 06-22-2007, 02:06 PM   #1
alordofchaos
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Default Guesses? burnt rubber smell, grinding noise...

Went out for lunch today... on the way back, heard a quiet grinding/clatter noise, wasn't sure it was me or not, car seemed to stumble a bit and lose power, and I smelled burnt rubber. I thought the sound was in the back.

Part of this is a blur because I was in full panic mode, wasn't sure at what point i turned off the engine, but I know the "!" light was on and I had no power - course, that might have been after I turned the car off so I don't know if the engine cut off or if I turned it off. Thought i heard some belt squeal, too.

My first thought was a belt - and I was fearing timing belt. pulled over, popped the hood (embarrassingly, used a broom stick to hold it open; new hood shocks arrive June 26). the accessory belts were fiine & tight, I had no way of inspecting the timing/balance belts. So... figuring that bending a few more valves wouldn't hurt, I got back in and turned the key.

Fired right up; drove the last half mile back to work with no problems. I don't think I ran over anything, but there is still a burnt rubber smell. A/C doesn't seem to be running quite right but I haven't really checked it because i got right back to work.

Any suggestions on what to look for when I get home tonight?
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Old 06-22-2007, 02:11 PM   #2
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Gut instinct on a quick read is that your AC compressor is going and you are spinning the belt on the seizing compressor pulley...
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Old 06-22-2007, 02:12 PM   #3
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Start car, turn on AC and watch compressor engage... if the belt slips... there you go
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Old 06-22-2007, 03:23 PM   #4
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Thanks, I'll take a look at that tonight! If the compressor starts going, it can stop intermittently?

I did push the AC button on and off a couple of times, don't know if it engaged, though. There was no squealing or anything for the brief time it was depressed.

I figured I'd wait til I got home before testing... didn't want to take a chance of the AC belt breaking and tangling up in something.
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Old 06-22-2007, 03:25 PM   #5
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watch the clutch engage on the compressor and spin it under load... if the belt starts having a fit and you smell rubber... badabing!
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Old 06-22-2007, 03:36 PM   #6
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still have the factory rubber center clutch???

just a guess but it could have sent a chunk of rubber flying through the bell housing and cause a burning smell, maybe even a squeel???

balance belt? any odd vibrations?

I'll brain storm other possibilities.
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Old 06-22-2007, 04:11 PM   #7
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When mine went it was a bunch of black powder, but that doesn't mean that yours has to be that way.

Either way, pop the inspection hole cover on the bell housing, and stick your finger in there and see if it comes up with black rubber on it.
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Old 06-22-2007, 04:19 PM   #8
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That sounds a lot like when my compressor seized up.

Fortunately, simply turning off the AC got me to keep on driving. I had to replace the belt ASAP, tho.

My first thought was that it might be the rubber clutch, but the more I think about the AC, the more I think that's the first place to look.

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Old 06-22-2007, 04:37 PM   #9
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I hope it's not a rubber-centered clutch... there's documentation that a PO replaced that around 105k or 110k miles (at 121k now).

Odd thing is that my passenger and I both thought the sound came from the back... but that might have been a trick of the sunroof being opened

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balance belt? any odd vibrations?
I hope not... it is another possibility that my t-belt and b-belt rubbed briefly. I'll look tonight. there was a brief vibration... I wasn't all that observant when I was panicking I think I shut off the engine and coasted to a stop at the side of the ride at the first sign of trouble (right after I thought, "Hey, I think that sound is coming from my car!"
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Old 06-22-2007, 05:07 PM   #10
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Just so you all know. Looking in the inspection hole will not always tell you that the rubber clutch center went bad. Mine would totally let the disc spin freely on the hub, but not one bit of rubber showed up in the inspection hole. it was a clean break all the way around the hub. As far as i know it made it to about 170,000 miles before it gave up.
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Old 06-22-2007, 05:34 PM   #11
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If it is the AC compressor - can it be repaired? New bearings, or something?

Or should I just go with a new compressor (and go to R134a while I'm at it)? Ouch, $$$

This is my punishment for thinking about selling, because I don't have time to work on it
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Old 06-22-2007, 05:41 PM   #12
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If it is the compressor, first of all the good news is that you won't likely have to replace it right away to drive the car. So long as you keep it turned off the car will be fine. Just make sure you replace the belt. That's what I did for about 8 months.

As for your options, I'm not aware of any rebuild kits out there, and I hear they aren't the easiest thing to rebuild. Rather, you can either get a rebuilt one $4-500 or find a used one. Give it a little time and you shouldn't have any trouble doing that.

Regarding which freon to use, that's up to you. I had originally planned on upgrading to a Sanden R134a compressor but decided that I didn't want to hack up the AC lines to make it happen. I ended up converting my 944 (and my Miata) to R134a, mainly because I could top the freon off on my own.

The Miata's converted AC works wonderfully. It kept my black-topped, black-interior'd convertible cool during the 95* and lots of humidity weather.

The 944's system doesn't work as well, but we suspect that it may have a clogged expansion valve. I haven't chased it down because I'll just settle with the Miata's AC right now if it's that bad. But I've heard other people in this area being happy with converting their R12 system to R134a, so if it were me I'd do it.

Make sure you have the system properly evac'd and replace your reciever drier it you choose to do that.

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Old 06-22-2007, 05:58 PM   #13
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Thanks, Brian!

I was using HFC-12 (foxcool) which was working great. I might stick with it, even if I make it R134a compatible.

I'm old, I need AC
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Old 06-23-2007, 03:42 AM   #14
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You seem to have been in such a panic the noise ans smell may have come from the car behind you.

I was traveling home yesterday and on the highway my wheelbearing became very noisy, I worried and pull over just to be past by the cause of the noise, a Landrover with offroad tyres.
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Old 06-25-2007, 12:51 PM   #15
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No one behind me or in front of me
The few minutes I was on the side of the road, only one car went by.

That's the plus side of living in the middle of nowhere.
On the minus side, I could have been a long time hitchhiking (would have called a tower) and I'm pretty much stuck with dial-up or satellite internet.

A traffic jam is when 70mph traffic has to slow to 60

Didn't get a chance to look this weekend, will try later this week or weekend.

Thanks again, everyone!
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Old 06-25-2007, 12:51 PM
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