high milage m20s

[bastianshaw]

I wanted to talk about high mileage m20s, seems to me, if the timing belts are kept up and you dont break a rocker arm the rings or main bearings will be the first thing to wear out am I right?

I know putting a mileage on this is tough but 200,000 would you agree that is getting up there?

I guess compression is what goes right?

[woodisgood]

Compression may be the first to go but I think the valves are the weak link, not the rings.

[Earendil]

I had my valve springs go first, at around 220,000 mi. At the time I did the valve stems, and the head bolts were the original old style, so I'm guessing the head hadn't really been touched. Pistons looked good at the time, and she's now getting up near 300,000.
Compression is still good.

Day's iX was bought with "180,000 miles" as shown by the odo, and I trusted the PO as be was a coworker and the compression was solid. Turns out the car was sold in 2003 with 240,000 miles on it. The car has to have over 300,000 miles on it by now. His head is dirty, but nothing has broken yet! I don't know if its had work done to it though, could have, but no records were passed on or mentioned if so.

The older the engine is, the more it matters how it was maintained and driven. Metal wares down slowly, but it does so a lot slower if taken care of.

[ROLLingKING]

Excellent question. I'm at 224,000 on my m20 and I abuse the poor thing. I'm trying to figure what should be addressed with a timing belt if I have time to remove the head and get a head and block resurfaced...so many moving parts to replace.

As of now I'm just collecting IE hd rockers, and vac's valve kit. VAC valve springs might make it in the budget and an IE regrinded cam I think will be a happy boosted m20. Hopefully by 300,000mi.

[jlevie]

If properly maintained, the first "thing to go" will be the head. Specifically wear in the valves, guides, and cam. The next will be wear in the cylinders and rings. Eventually there will be enough wear in the bearings and oil pump to cause problems.

[South26]

at 225,000 my bearings went. I lost oil pressure. The pump was fine. When I removed the bearings they were nice and worn. The car did great until 300,000 miles when the car was hit by a pick-up truck.


Andy

[Baxter Auburn]

When i purchased my 325i it had 324k miles on it but was properly maintained by a local bmw dealer the engine had all stock major components never had a broken rocker arm no head problems and decent compression, i ended up driving up to 336k miles before deciding to do a full rebuild but even at that time it was still running perfectly fine.

[bastianshaw]

what was compression before rebuild?

[603Racing]

179,000 miles on mine when the bearings went. Of course my oil light did not work and I drove around for about 3 days (200 miles) with very low oil pressure. I had no signs of problems until I started to hear engine noises. The car was used as a track/DE/AutoX car for two summers before I bought it, so that's the likely cause of the early wear.

[jlevie]

179,000 miles on mine when the bearings went. Of course my oil light did not work and I drove around for about 3 days (200 miles) with very low oil pressure. I had no signs of problems until I started to hear engine noises. The car was used as a track/DE/AutoX car for two summers before I bought it, so that's the likely cause of the early wear.

Unless the engine had at least a crank scraper, the track use is probably what set the stage for the bearing failure.

[ROLLingKING]

M20's rock

[Cabriolet]

what was compression before rebuild?

No, leakdown first. compression tests hide issues.

[Earendil]

M20's rockers break

FTFY.


M20's are great until you rev too high and one of your rockers snaps in two. It's certainly one of the weakest links in the engine when trying to push the M20.

[ForcedFirebird]

Just puled an m20 out of a car with over 360,000 on the odo that broke 2yrs ago. Still ran like a champ, but puffed a little blue smoke. Maintenance records dating back to 30k miles.

[bastianshaw]

M20's rock

word