928wolf

I got quite a scare yesterday, pulling out of my neighborhood, getting on it pretty good I smelled smoke, then I saw a puff of smoke, engine stumbled and my CWL started flashing. Not good. I was only about a half mile from home so I limped the car back to house.

Come to find out, the housing on my alternator broke and the belt was gone, or so I thought. So, at very least it looks like I need a new alternator and belt, a pray nothing else went wrong.

Question: Could the sudden loss of the alternator cause any cascading electrical problems? The car still ran, but all my dash lights were on, CWT was flashing and my battery voltage gauge was showing no voltage. I'm pretty sure all the alternator does is charge the battery, and the battery acts a buffer for the rest of the electrical system. Am I right or do I have more potential worries once I get my alternator replaced?

While taking pictures and video under the car (how great a tool is a camera phone for diagnostics, BTW?) I noticed a shredded air duct and what I think is the remnants of the alternator belt. Possibly casualties of this sudden failure. I haven't gotten a chance to jack up the car and really dig in yet.

Anybody ever have this happen, and am I in for some nasty electrical problems?

928wolf

1985 Euro, 5-Speed, if it matters.

OTR18WHEELER

The battery is really just to start the car, the alternator powers the electrics while the car is running. Can you see the wire harness behind the alternator?, it may have gotten pinched against the oil pan or something. check closely to make sure none of the mounting points to the block or cracked or broken when you take it off. Disconnect the battery first.

James Bailey

Your engine is riding too low...collapsed motor mounts and the alternator has hit the ground or a curb in the past. It OFTEN breaks the engine block where the alternator bracket bolts on....good luck to you as you may need it....

Alan

The alternator should provide all power most of the time the car is running, it also recharges the battery.

If the alternator stops generating the car will run on the battery alone.

When the alternator stops generating all the warning lights will come on.

Likely the alternator is electrically OK - and its very unlikely this did any other electrical damage except perhaps to the alternator connections (check those wires) you can probably have the mounting tab welded back on if thats all that is broken...? Check also for what else the alternator body may have hit (manifold?)

However as Jim says you are likely too low (suspension/engine) and you have no undertray.... You are actually lucky - breaking the mounts off the block would be a much bigger deal here.

You need to make some changes to prevent it happening again - its likely an aluminum undertray alone would have prevented this. But fixing engine & ride height is also worth lookling at.

Alan

dr bob

What Jim Said... ^^^

Disconnect the battery if you haven't done so already.

The alternator hangs on an aluminum "console" bracket that's shared with the power steering pump. Besides the adjustment mechanism visible in your picture, there's a long through-bolt that holds the top of the alternator between the console bracket and the block. The top of the alternator where it pivots is a lot more stout than the 'adjuster' end in the picture. While it's possible the top bracket broke, the more populat failure is that the console bracket breaks or is pulled down and back, as the bolt breaks the boss in the block at the rear of the pivot end of the alternator case. You'll know the extent of the damage once you can get the alternator removed.

If the block isn't damaged, the aluminum console is available used from 928 International. They also have the alternator and replacements for any bent bolts. If the block itself is damaged, you'll need to assess the severity and decide what your repair options might be. I think there are four or five bolts that pass through the console into the block, including the pivot bolt for the alternator. One other large one adjacent to the pivot bolt, three 8mm (13mm head) bolts into the block closer to the crank pulley. The bolt that holds the adjuster only threads into the console, doesn't pass through to the block. There are three adjuster bolts on mine that hold the power steering section into the console, and three more that hold the sliding section to the power steering pump.

The smoke: Could be the belt burning after the alternator seized. Burning rubber has a particular fragrance, and the failure would include squeeling as the belt tried to turn the frozen alternator. Less desirable option is that the wiring on the back of the alternator was pinched and shorted to something behind. With the primary (B+) connection grounded, the car would stop almost immediately due to loss of both alternator and battery feed to the CE panel consumers. IIRC, the oil cooler hoses, pressure sender, and oil filter are in close proximity behind. Inspect for damage to those pieces while you have everything apart.

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It looks like there's a scrape or broken edge at the lower inner front face of the alternator case. I'll speculate that it hit a parking bumper or similar. As others point out, the engine appears to be setting pretty low. That's commonly caused by a combination of collapsed motor mounts and sagging front springs. May also include intentional lowering of the front suspension sometime in the car's lifetime. Regardless, fragile engine bits end up closer to the road, exposed to damage from anything taller than those few remaining inches of clearance. Or any road defect like a pothole or pavement defect deeper than those few remaining inches. I regularly preach the benefits of maintaining ride heights within original factory specs, and this is a pretty graphic example of a top reason to honor those values.


Good luck with the damage recovery process. Please take and post more pics along the way as you catalog the damage.

928wolf

Yikes!

I did bottom out recently, but didn't think anything of it. Assumed I got the front spoiler. Obviously not.

I thought It was odd all that stuff was that low and unprotected. So it looks like I need an undertray and to fix my ride height. Is that what the empty hooks under the radiator are for?

How do you check ride height and what should it measure?

Thanks for all the help, I'll report back.

Wisconsin Joe

Good luck finding an undertray. They are darned near impossible to locate for an "SOB."

You will need to replace the Motor Mounts to get the engine up. Roger has the Volvo ones for a decent price. Not an easy job, but doable for the determined and somewhat skilled.
The bottom of the oil pan should be nearly level with the bottom of the crossmember.

Ride height measurement and specs can be found through this thread:
https://rennlist.com/forums/928-foru...questions.html

928wolf

OK, I measured the ride height with an almost empty tank of fuel.

Front: 130-135 mm
Rear: 165-170 mm
Clearance (at lowest point): 95-100 mm

Based on the ride height specs I am definitely low on the front, not bad in the rear and too low in overall clearance.

The specs say 180 +/- 20, but allow another 10 mm of "settling" over time. That means the absolute minimum is 150mm, with the consensus on another thread that seemed to hover around 165-170 for street use.

The owner's manual says minimum overall clearance of 120mm with full fuel tank. The lowest point I could find and easily measure was just shy of 100mm.

The front and the overall clearance numbers are off by similar amounts, so hopefully that means the suspension is riding low, not collapsed motor mounts. It looks like that is the easier problem to solve.

If my motor mounts were collapsed, is there an easy way to know? Subjectively, my engine feels like it has more motor vibration than it should, especially when it's not all the way warmed up. But that's not based on any comparison with other 928's, since this is the only one I've ever driven. My wife's V-6 Mitsubishi Eclipse is much a smoother revving engine even at 6000 rpm, but that may or may not be a good comparison.

I definitely need an under-tray to protect these components. If I can't find a production version, I have 12 engineers who work for me, one of them could whip me up a design in Solidworks in an hour, and I can get it made at local machine shop. But I'd rather have something stock on the car.....

Thanks again for all the help, what a fantastic wealth of knowledge this site is!

Alan

I'd not recommend you get a stock undertray - get the aluminum one from 928 International (but it depends on year) - it will provide you with much better protection than the plastic Porsche version, and fits well.

Alan

dr bob

You can 'check' the motor mounts by sticking a finger or three between the two safety hooks that straddle the motor mounts. These are interlocking steel hooks formed into the plates on top of and below each mount. They are intended to prevent the mounts from over-extending, and when factory mounts are new the hooks are almost touching. If you can get a whole finger in between the hooks, your mounts are pretty much used up. Two fingers in there means they are completely collapsed. New mounts generally hold the engine up so the bottom of the oil sump is no lower than the crossmember, for a yardstick indicator. The hook clearance is the definitive test though.

928porschemangreg

Guess I dodged a bullet also. When I bought my car, the Alternator housing was scraped like from speedbumps. Suspension way low, Pans and Air dams ripped off. I saved its future by first adjusting the ride height and new shocks.

928wolf

OK, I was able to jack the car up and get a better look. What I was able to figure out is that on my model there is an alternator bracket that also mounts the air pump, and it is mounted to the engine block. I found a big crack in it as well so I am becoming more confident that I haven't cracked the engine block. I couldn't actually get a picture of the crack with my phone but I saw it with my eye and felt it.

So it looks like I can replace the alternator, the alternator bracket, and I'm going to replace the regulator and condenser just in case they got damaged. Unfortunately, it appears that the only way to get the alternator out is to remove the cooling hose going to the thermostat, so I may get a coolant change out of this whether I want it or not. I'm looking at $400 to $500 total right now. I feel lucky.

.....then I've got to figure out my other problems with my car sitting too low and a potential motor mount change in my future.....

James Bailey

The pump is the power steering pump. 928 International will have a good used console mount and a good used alternator.....worth a call to Tom 714 632-9288 . You access the alternator from below pretty simple task really.

FredR

This is what I call the "928 *** in the air" syndrome- either failed engine mounts, soggy front springs, incorrect ride height adjustments or combinations thereof.

Besides the alloy front undertray you should also consider Carl's bump plates- they would probably have stopped this from happening [mine are well ground on the under side and still going strong.

On a car that naturally is designed to understeer, front end low just exacerbates this charaacteristic given it places more weight up front.

Regards

Fred