'89 535i M30B35 head gasket replacement

[Dash01]

This car lost coolant and heated to less than the high temperature mark before replacing lost coolant with warm water to avoid thermal shock. It was then driven several miles home with the temperature reaching about half way between normal temperature and the high temp. mark. It had some steam from the tailpipe upon start and for about 1/4 mile, then some blue smoke for about 1/4 mile, then normal tailpipe emission with no steam or blue smoke for several miles. The now-drained oil is dark brown (about the color of Hershey chocolate syrup) but not frothy or milkshake. Dipstick oil looks and smells normal. No oil in coolant.

I bought a new replacement head gasket, head bolts, and valve cover gasket. Also have a new machinist straight-edge. The old head bolts have been loosened in correct order before removing the head.

Now the question is whether such a head needs to be resurfaced at a machine shop, or whether installation of the new head gasket will be OK after cleaning residue off the head and block mating surfaces, assuming the straight-edge shows the head and block to be within ~0.004" flatness tolerance.

If within flatness tolerances, what are my chances of simply cleaning the surfaces and installing new gaskets, then torquing bolts to spec, for a reliable engine?

How best to proceed? How best to clean gasket surfaces?

Thanks, in advance!

[theBMWbeast]

I did just this about 2 years and 15k miles ago. And my straight edge was less than straight lol

Razor blades, plastic scrapers, Brillo pads, sandpaper, shaving cream, and a lot of time are the tools I used. Have pics somewhere.

Car had 180psi compression after the new head gasket, between all cylinders if I am remembering correctly. Just put down 168whp and 195wtq on the dyno 2 weeks ago. As long as it’s straight, you should be fine.

[cirrusblau]

Do the while-you're-in-there jobs like gaskets (rear of the head, intake, exhaust, thermostat housing, upper timing chain cover), and if you're going to send the head to the machine shop, might as well do the valve seals. It's a fairly easy job, it would be faster if you just disconnect the downpipes and leave the intake manifold on.

[Dash01]

I did just this about 2 years and 15k miles ago. And my straight edge was less than straight lol

Razor blades, plastic scrapers, Brillo pads, sandpaper, shaving cream, and a lot of time are the tools I used. Have pics somewhere.

Car had 180psi compression after the new head gasket, between all cylinders if I am remembering correctly. Just put down 168whp and 195wtq on the dyno 2 weeks ago. As long as it’s straight, you should be fine.

What tools in particular did you use on the aluminum head?

I ask because I don't want to screw this up. Am considering using my brand new steel straight-edge not only as such, but also as a sanding block by attaching emory cloth. Shaving cream as lubricant? That would catch all grit and contain it.

[theBMWbeast]

It's been a second. I don't remember it to the letter, but the process should be the same for the block and the head. You wanna use super fine grit, 1000 etc, for the head. Or atleast I venture on the safe side for the aluminum. The iron block can take a harsher grit without losing material. You obviously only want to try and remove gasket material.
Only wetsand, and don't let it build up. You want to keep everything clean as possible. Also, don't get caught chasing down stains. If you can catch your fingernail on gasket material, it needs to be removed. If not, it should be fine. You start chasing discoloration or stains and you'll eventually remove some metal. A straight sandingblock is key, and keeping your hand level as well. Don't go at angled trying to get at a specific thing. Keep it flat.


You fill the coolant passages with shaving cream, so the small grit doesn't get into the block. Then a straw taped to a vacuum hose and you suction it all out.

Here's some pics from when I did the same procedure on the m103 in my merc wagon (I did this in one day, just needed to get the car running, suprisingly the gasket took care of the pitting you see. If this was my BMW I would have had it machined at that point. Either way, these photos are back from August, knock on wood). You cannot have major defects between coolant and oil passages, as a gasket can only do so much at pressure.

[ross1]

You fill the coolant passages with shaving cream, so the small grit doesn't get into the block. Then a straw taped to a vacuum hose and you suction it all out.

Brilliant!