From digest.v7.n1476 Wed Apr 8 12:43:03 1998
From: poffen_at_San-Jose.ate.slb.com (Russ Poffenberger)
Date: Wed, 8 Apr 1998 06:58:55 -0700 (PDT)
Subject: <E34> Re: M20 525i Prone Problems?
> From: Eugene Hoe H W - TCD <eugene_at_csam.com.my>
> Date: Wed, 8 Apr 1998 14:30:00 +0800 (SGT)
> Subject: E34 M20 525i Prone Problems?
> Hi all,
> I heard a rumour that the M20 520i and 525i has a reputation of having
> cracked cylinder heads when
> the car is driven hard often. Can anyone verify this, how true is this?.
> Any other potential problems
> the M20 525i engine has I should know about?.
The M20 head does have a design weakness. The problem is the coolant inlet port from the engine around cylinder 5. The port is too small, meaning that insufficient coolant may reach there. The symptom is a crack, usually at the top of the head, just under the cam, between cylinder 5 and 6. I had one go exactly like that a few years back in my 1990 325i (read $$$$).
One solution that applies to me now, is a Metric Mechanic sport head. They modify the port and supply a special head gasket that improves flow.
The M20 engine also has a weakness in the oil pump. You can read about some of this stuff_at_www.metricmechanic.com
Another MAY be to use redline water wetter. While I don't claim that it does all it is supposed to, but if it does, if could help the situation some.
1998 Jeep Wrangler Sport
BMW CCA# 138716