Gut check : considering M5 : another chain rail question

[Heilerin]

Hey fellas. Been hovering in this forum for quite some time, learning quite a bit about these great cars. Seems everyone here has some area of expertise so I thought I would (finaly) ask in detail about a car I am considering.

It's a black 1988 M5 and while the suspension, belts hoses etc have been sorted, it is now well over 100k, without the chain rail guides being replaced. I know this is a topic of concern, mostly due to age and not neglect. I'm confident the chain itself is fine, but potentially grenading an engine and incurring the costs of an engine build is something I'm not comfortable with.

I am also currently trying to determine when basic crucial maintenance was performed (valve adjustment and mechanicals)

The rest of the car seems well kept but I do have a few questions.

1. What is an estimated cost for replacing the chain guides? And what else ought to be done while that's underway?

2. Considering the rest of the car is well kept, should that cost be negotiated from the asking price?

I understand that I'm asking these questions to an enthusiast group, but also I'm trying to minimize any (large) financial costs if I end up with the car.

I can PM anyone with specific details on the car, but for this discussion I was interested to hear your thoughts about the tensioner vs age and mileage on an M5 for sale.

[TheE28Ranch]

I think I spent a bit over $2100 for parts and labor to have it done - but I didn't have much of a choice due to space and time available to take a crack at it myself. I am also a shadetree mechanic type - I'm sure I could figure it out, but what if something went wrong? I'll get paid doing what I do professionally. I figured $2,100 for preventative maintance was better than a $6,000+ rebuild. I wouldn't just take it anywhere though, if that was the case I would have waited and done it myself.

Kinda vague answer and only addresses one or two of your queries...but I'm kinda passing through right now while working at the desk....

Lots of nice M5's out there FS right now, too.

[Randomg]

I know this is a topic of concern, mostly due to age and not neglect.

If you want my opinion on it, I disagree with this statement. The cars that have had problems have ranged in mileage as well as in age. I think letting the car warm up for a few minutes before giving it more than 1/3rd throttle is the key. I used to fret about the chain guides, 40k miles later @ 186k miles, I don't worry about it anymore.

I think a very small percentage of M5s have had this problem, but everyone worries about it. Most mechanics you talk to tell you not to bother. Somebody correct me if I'm wrong, but it's been years since I saw an s38 grenade due to chain guides. That said, I wouldn't want to be the reason you buy it, only for you to need an engine rebuild.

[rcbmw]

Attention must be paid to rail--heat cycling and age are factors in the failures.

Best,
RCBMW

[Heilerin]

I know this is a topic of concern, mostly due to age and not neglect.

If you want my opinion on it, I disagree with this statement. The cars that have had problems have ranged in mileage as well as in age. I think letting the car warm up for a few minutes before giving it more than 1/3rd throttle is the key. I used to fret about the chain guides, 40k miles later @ 186k miles, I don't worry about it anymore.

I think a very small percentage of M5s have had this problem, but everyone worries about it. Most mechanics you talk to tell you not to bother. Somebody correct me if I'm wrong, but it's been years since I saw an s38 grenade due to chain guides. That said, I wouldn't want to be the reason you buy it, only for you to need an engine rebuild.

I understand what you're getting at, perhaps my earlier post was misleading.

I know older polymers became more like bakelite (I'm exaggerating here) and were subject to brittleness because of age and heat cycling. I spoke at length to a respected BMW tech who described what to look for with regard to the chain tensioner color and condition. If I can get a personal look at it I'd feel infinitely more comfortable. His recommendation was mostly keep it maintained and change the oil frequently. Of course he recommended renewing the tensioner for preventative measures. . .

[Philo]

My head, chain and guides were done at 260k roughly.

http://phil.files.infostreet.com/M5_Ima ... 300070.JPG

http://phil.files.infostreet.com/M5_Ima ... 300072.JPG

http://phil.files.infostreet.com/M5_Ima ... CT0016.JPG

[Rich Euro M5]

My head, chain and guides were done at 260k roughly.

http://phil.files.infostreet.com/M5_Ima ... CT0016.JPG

The orange piece is the chain guide, I believe it's made of Delrin and was originally white in color. This is the part that grenaded the engine is Scottie Sharp's M5.

Not replacing the chain guides and tensioner in a 22 Y.O. M5 engine is taking a big chance.

To the OP, to do the minimum will set you back about $1k in parts. If you can't do the wrenching, add the labor rate. FWIW: The cost of a engine rebuild using aftermarket pistons, and not modifying anything will cost about $7k in parts and basic machine work. If you ship the car to Korman, it'll run you about $10k - $12k for a standard overhaul of the S38B35 engine.

Rich

[Cory]

From what I gather is that it's not necessary unless there's signs of needing to be addressed. From what I'm told, too, by those who know a lot more than me is that our engines (most engines I would think) slowly degrade over time so maybe a top-end overhaul would be a good thing to do when funds are aplenty and, of course, a timing chain/components overhaul would be a part of that (along with maybe a porting cleanup and some cams).

[88 M5]

I did a lot of research like you did before I bought my e28 M5 and finally did buy it. I talked extensively to The local BMW shop here to the owner/mechanic who has been working on these cars for over 25 years. He told me that they start making noise just before they go, and to buy the car and drive it. So I have been. I'm going to get it done anyway next spring after I sell my current winter car using the funds from that. better safe than sorry I figure. They are amazing cars. buy it.

[eastside_m5]

I feel the need to replace the chain guides soon.
Does anyone have a list of part that should be replaced?

[bojangles]

The orange piece is the chain guide, I believe it's made of Delrin and was originally white in color. This is the part that grenaded the engine is Scottie Sharp's M5.
Rich

Has this every been really figured out?
I followed Scottie's story back then, and I know he drew some conclusions.

The technical proof is hard to see tho. After the grenade, everything was wrecked, and I still dont know if we can say 100% that is was the guide first. There is a strong possibility that the tensionner was loose, the chain slapping and that broke the guide.

It does not change the solution, nor the danger of a big failure. Just that it is already at the "internet legend" status and not a proven story.
The timing chain, rails, guides, and tensionner will eventually fail and likely go further to screw the valves, pistons, and even maybe bust apart the cam tray.

If we only knew the real weak link, we could reduce the cost of this preventative repair. Certainly would be a simple thing to just change the tensionner if it gets noisy.