Tuesday, August 16, 2016

W126: Heater Connection Leak at Cylinder Head OM603

OK, so if you all may remember the cracked #14 head debacle I did earlier this year it needed to come back for a minute leak from the heater connection pipe at the back of the cylinder head. It manifested itself after the owner of the car drove it for a bit, not while it was under the knife - go figure.

Can catch up on that last post here: #14 Cylinder Head Work 300SDL

Had him bring it back to me to take care of what I figured was a torn o-ring at the connection. No big deal, I have about 50 of these rings as I reseal that connection rather frequently on multiple cars.

After removing the intake manifold, etc turns out the leak was from the actual heater connection piece that screws into the cylinder head and has a seal ring. After removing it, I found boogered threads and the damn connection piece was stripped! Not exactly sure how this happened, as I was the only one doing the work....

Anyhow, I needed to chase the threads in the cylinder head, a $70 tap later I can get to work.


The tap at work. Heater connection thread sizing is M22x1.50 for anyone who'd like to know. Nothing of the sort showed up for me using google so here you go! Bit of cutting oil to smoothen the operation and you're good to go. Make sure the tap you use is closed end, you want to chase threads to the base, not start new threads. You won't have enough room with any other tap. 

And this is the machining masterpiece to be replaced. It's made of a softer aluminum than the head, so it's threads will work off into the head (which the tap removes) to not destroy the head. If it's been overtightened by a behemoth then it'll strip. If it's fused to the dang head, it'll strip.

When installing a new one, I chose to run a very thin layer of teflon tape on the threaded portion to help seal things off.

Part numbers

601 203 0136 - Heater Connector
N 007603 022100 - Sealing Ring

You need one of each to install. Should cost you under $30 for the two and you're good to go - or you know, don't strip it....

I do warranty my work, so this is gratis for the customer. If there's something I was working on that isn't 100% up to par, I will fix it properly. This just happened to be a freak occurrence, I've only ever had to do warranty work on 2 cars in 8 years. I'm doing alright, I guess.

Thanks for reading! Allen


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