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TOPIC: Overheating 88

Overheating 88 06 Oct 2012 05:48 #11670


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Morning All. I am hopeful for a quick solution. I purchased a 70k 88 S4 about a month ago and I just completed a full service. Including the two engine cooling fans, water pump, timing belt all other belts, hoses, changed out fluids and so on . When I bought the car the drivers side cooling fan was Inop so I replaced both just to be safe. The same fan will not work and my engine runs hot under normal driving conditions about 80 degree's. The fuses are ok. I can't tell if the cooling flaps are working but when the engine is shut off they appear to be open maybe they are stuck in that position. I am NOT an astute 928 technician very much at the bottom end of the learning curve. I am reaching out to anyone who may have any idea's how I can get past this problem? It's been killing me to look at this Black beauty just sitting in my driveway. Please
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Overheating 88 06 Oct 2012 08:08 #11675


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First things to check are the fuses - each fan has its own fuse. They are numbers 28 and 29 in an '88.

Be sure to not only look to see if the fuse is burnt out from load, but also if there is evidence of corrosion in the fuse sockets - very common. One of mine had corrosion that caused the fuse to overheat and partially melt due to local resistance, although it had not burnt out from excess current load.
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Overheating 88 06 Oct 2012 09:06 #11676


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martinss;12020 wrote:
First things to check are the fuses - each fan has its own fuse. They are numbers 28 and 29 in an '88.

Be sure to not only look to see if the fuse is burnt out from load, but also if there is evidence of corrosion in the fuse sockets - very common. One of mine had corrosion that caused the fuse to overheat and partially melt due to local resistance, although it had not burnt out from excess current load.

As Martin has advised, be 100% sure that you have *good* connections at both fuses.

The problem may be the final stages module. You can either rebuild or replace it. You may also get by with simply taking it apart and cleaning it. If I had a bet on it, I would wage that the final stages module were your culprit.
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Overheating 88 06 Oct 2012 09:59 #11678


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As Martin and Austin have said, the power connections are the most common problem.

Every 928 owner needs a test light. The best type looks like an old-fashioned ice pick with a clear handle and an attached wire. The handle contains a 12-volt light bulb, and the wire ends in an alligator clip. In use, you attach the alligator clip to a known-good chassis ground, and touch the sharp tip of the tester to the suspect connection. If you have power, the bulb lights up.

Check both fuses. Look closely at the end of the fuse, and you will see two little metal dots. One dot is power in, the other power out. You should have power on both dots of both fuses. If not, check the medium-sized red wires on the battery positive terminal. It is a good idea to disconnect the battery ground strap from the body, then carefully clean every connection on the battery.

If you are certain that you have power thru the fuses, you can test the fan final power stages. This is the finned black box on the panel in front of the radiator. If you are good with a soldering iron, you can probably fix a faulty unit, but it might be better to check the 928 vendors for a rebuilt unit.

It is a really good thing that you are trying to do your own repairs, maintenance and upgrades. We will be here to help. If you want help, give complete info on your car, including model year, USA or RoW, five-speed or auto, etc. Give a complete description of the problem - the more detail, the better. And, it would be nice to know who you are, but that isn't required...
Wally Plumley
928 Specialists
www.928gt.com
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Overheating 88 06 Oct 2012 14:55 #11685


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I am extremely grateful for all of your thoughts and idea's. I will head out to grab a test meter and check these things out. As a side note.
My name is Robert. Live in Nashville and I own a 1988 S4 Auto with just under 75k. I recently purchased this car.Its history is somewhat unique in that the previous owner was a world famous drummer who barely drove the it. I am slowly going over everything. Having said that I am quite sure that I will be back to steal more of your priceless knowledge. My other cars are a 76 930 with 18k and a 78 911 with 34k.

Many Thanks
Robert
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Overheating 88 06 Oct 2012 15:20 #11688


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Robert,

Make sure you report back your findings. We're all happy to help.
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Overheating 88 06 Oct 2012 20:52 #11692


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Robert, my '95 had a problem and the passenger side fan would not come on... Ended up being the damn speed controller! $300 used, $600 rebuilt...$zillion new from Porsche (if even available). Hope that is not your problem, but would be dollars to donuts it is. These things are starting to drop like flies.

That said, my '88 auto has NEVER run hot. It always runs cool. I suspect something didn't get put back together correctly when all those things you mentioned were changed out (assuming it was not running hot before and that is why they were changed in the first place).

These guys here know their stuff. Listen to them.

Sounds like a nice P-car collection! Great stuff!
James
78 Silver / Black-white #295
84 Ruby Red / Black AO84
88 Dark Blue / Linen-Black
92 Polar Silver / Dark Blue 92EURO
93 Arrow Blue / Black
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Overheating 88 07 Oct 2012 13:48 #11703


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Hi Robert,
Hopefully you have solved your problem.
On the cooling flaps - these do give problems and one way of avoiding issues is to leave them open. If they are open just pull fuse number #23 and they will stay open.
Roger
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Overheating 88 07 Oct 2012 19:53 #11708


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Thank you all again for your valuable feedback. To answer James question. I did not know that fan was inop till arriving home with the car. I ordered both used from 928 INT just to be safe. Of course it remains dead. I have checked the fuses associated with the cooling fans and both appear fine. I then removed the potential culprit "output final stages unit" and examined its connection but of course found nothing. I have checked several sources for a replacement with no luck so far. 928 Int does not even list that part new or used. I sent a request to pelican with that # hope to here back. The blessing would be If I could manage to find a used one they are indeed very expensive it appears. I drove the car this weekend did not run hot but the outside temp hovered around 55. If anyone can help with locating this particular problem part I would be very grateful.

Again many thanks

Robert
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Overheating 88 09 Oct 2012 18:13 #11742


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Call Mark and Tom at 928Intl, they may not list it but probably have one... Roger may have one too, but I don't know how many used parts he keeps around...mostly new stuff at 928sRus.
James
78 Silver / Black-white #295
84 Ruby Red / Black AO84
88 Dark Blue / Linen-Black
92 Polar Silver / Dark Blue 92EURO
93 Arrow Blue / Black
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Overheating 88 10 Oct 2012 18:23 #11759


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Thank you all for your sharing your knowledge and wisdom. In fact the issue was the Final Stages Fan Module.:)
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Overheating 88 10 Oct 2012 19:01 #11761


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PCA0891;12104 wrote:
Thank you all for your sharing your knowledge and wisdom. In fact the issue was the Final Stages Fan Module.:)

Glad we were able to help! :cool:
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Overheating 88 10 Oct 2012 23:14 #11768


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Yea, I guessed right! BOOOO you had to buy a fan module! :) These things are dropping fast these days. My bad one was on the '95 GTS of all things!
James
78 Silver / Black-white #295
84 Ruby Red / Black AO84
88 Dark Blue / Linen-Black
92 Polar Silver / Dark Blue 92EURO
93 Arrow Blue / Black
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