1990 420SEL head R/R??? - PeachParts Mercedes-Benz Forum

Surf-n-Turf · #1 10-30-2007, 10:47 PM

Just got a 420SEL with 3 bent valves on 1 head. So I have been told anyway.

Is there anything "unique" with removal and replacement of the heads on these? The guy I got it from says the 3 mechanics that told him the valves were the issue, also went on to a spiel about how hard it is to remove and replace the heads.

BTW, the car is BEAUTIFUL!!!!!!! I had to get it even if I replace the engine.

#2 10-30-2007, 11:00 PM

There is nothing real special about the head r&r except for a couple of things.

First off, you will need a few special tools to remove the head bolts, you can find them on the internet for not too much money.

The second part might or might not scare you. Sometimes the head bolts threads in the block strip out, and they have be re-threaded with a special jig that few people have anymore. It doesn't happen everytime, but it is a risk you should be aware of.

The last unkown I can think off is that the head will probably need new valve guides, because most of the one's that I have seen bend valves also crack the valve guides at the same time.

Lots of people have done this job at home, the biggest pain is finding a reliable and honest machinist who can fix the heads.

david s poole · #3 10-31-2007, 11:46 AM

those are steel head bolts into aluminum block.it's no a matter of if the threads will break but when.murphy's law says that it will happen when you are torquing down the repaired head.ask me how i know.if you pull the heads the bolt holes will need to be helicoiled.only exception if already done.

lesrrt · #4 11-01-2007, 02:02 PM

I did my headgaskets a couple of years ago on my 380 and did not have any problems. Get the special tools above;being lined-up with the bolts before cracking them loose will give a good chance of not damaging them. Also, use air to remove the sludge within the hex bolt head to guarantee full hex tool seat. I would do both gaskets too and change out all seals. Mine has not burned any oil since with 175k mi. Good luck.