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M-100 thermostat housing, revisited

Started by TJ 450, 30 December 2009, 09:19 AM

TJ 450

My 6.9's thermostat housing has a fracture around the flange area, horizontally, that extends into the main coolant passage. It was seeping and the bolts also backed out such that coolant was squirting out at the base.

A stopgap repair using epoxy putty has put the leak at bay until I purchase a new housing. I also replaced the gasket with a new one that I made up.

I have always had great difficulty with the flange bolts and hole alignment as well as the intake manifold hose. The intake manifold appears 3-4mm too low, when compared to the housing. Is this a common situation?

I used a long bolt as a stud to help with the location.

Down time was only a few hours and I was out and about in it today. Apologies for the poor photography. It's always a difficult part to capture holistically. ;)



I used Loctite Red anaerobic sealant this time, just like on my chain tensioner flange that is finally bone dry after filing flat and replacing the gasket yet again.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

WGB

Thermostat housings seem problematic but fortunately I have been spared that.

I have also escaped any problems with my timing chain tensioner housing but have yet to re-explore that when I tdc my timing chain.

What I find problematic with the timing chain housing is that the closing  ring torque seems inordinately high while no torque value is given for the two small bolts.

I erred on the low side with the ring torque (30nm instead of the 40 nm from memory) and have had no issues whatsoever.

I am sure we have discussed this before but  I assume you do not have one of the early 8mm tensioner housings.

Bill

TJ 450

With the chain tensioner, I used your lower torque figures and just nipped up the threaded ring. FWIW, there was lots of chain noise before, so a leaking flange equates to a loose chain. It's very quiet now.

Anyway, back to the thermostat housing...
I broke it whilst trying to remove the seized thermostat cover. It took me at least a week to remove it and even after reading PB's advice, I still broke it. Very fragile they are, and even a rubber mallet will break them.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

koan

The water passages on thermostat housing and inlet manifold line up perfectly on my engine, Don't know what could be the cause of a misalignment there, i doubt the inlet manifold could be machined that much without upsetting the alignment of the cylinder head bolt holes.

Is it possible the leg that sits on the water pump is too long?

I had trouble getting the cover off the housing first time, resorted to hammer and block of wood, it survived. This was before PB's warning. Several subsequent removals have been finger jobs, no force required.

The housing had some corrosion around the hose connections which I cleaned up and filled with epoxy putty, this seems to have stopped further rot.

I've been lucky to have not suffered the seized and broken bolts other folks have encountered, about the only thing I've not done is separate the water pump from the housing. With these problems in mind I always use some anti-seize compound on bolts going into aluminium.

koan
Boogity, Boogity, Boogity, Amen!

Big_Richard

Quote from: koan on 30 December 2009, 03:17 PM
I've been lucky to have not suffered the seized and broken bolts other folks have encountered, about the only thing I've not done is separate the water pump from the housing. With these problems in mind I always use some anti-seize compound on bolts going into aluminium.

koan


You are a very wise man Mr Koan.

Just the other day while shopping at Malz i discovered some anti seize compound and wondered WTF that's for. Now that i know its usefull for screwing into aluminium, it'll be on my shopping list next time ;)


after 7 years of 6.9 ownership, i'm still learning something new everyday ;)

SELfor50

Is the Anti-seize compound the copper pasty stuff that is good to put on Spark plugs too?  We put that on the plugs on the track car when we service it at a mates shop.  Works good when removing them.

My thermo housing was swapped off my old engine, the new one had corroded as well and was almost tooth like at certain points..
Thankfully there was no snapped bolts when I swapped them out though thankfully.

TJ 450

I've been using some non-metallic anti-seize compound on any bolt or nut that is likely to seize. It works pretty well.

Cooling systems don't like sitting with air in them, it seems.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

oscar

#7
TJ, you need... 
TECHNOWELD weld,weld, weld http://www.youtube.com/watch?v=nxtmt6QCVd8
or
DURAFIX fix,fix, fix http://www.youtube.com/watch?v=jijW310xvp4
and once you've tried these rods out or something similar you can get back to us  ;D ;D Please.

For something that looks perfect for a repair like yours I still can't get something similar from my local engineering place.  You can only order online  :-\ but I've been itching to try some, or have someone else repair something like cracked cast alloy.
http://www.durafix.com.au/index.php

1973 350SE, my first & fave

koan

I'm amazed at the apparent ease of repairs in the demos (and I like the contrast in voice overs too ;)

Another video worth a look is

HTS-2000

I had some aluminium solder years ago that was useless.

koan
Boogity, Boogity, Boogity, Amen!

oscar

Ah good vid.  I want some.  I love the thread repair and casing repairs plus what about the cylinder head repair.  Once again why don't engineering shops sell this stuff and why do all the ads look ancient.  The repairs they do do olook quick and easy but the occasional novice vid seeem to do it all wrong.  It's funny some of the youtube arguments arising over whether it is strictly welding or not.  Someone says it's brazing, one will call it soldering, another says it's crap, others say it's brilliant and the occasional one wants TJ to be the guineapig   :D
I think part 2 of the technoweld video shows the "scientific" explanation of how the low melt stuff mixes and "welds" to the alloy.   Sounds convincing.
1973 350SE, my first & fave

koan

One of videos gives a reasonable explanation about it being welding, it certainly looks pretty strong - if the bending and banging are for real.

The clips do look pretty ancient, don't know  why there's not more of the product around - maybe it's not as good as they make out.

Need to get some and try it out, see if it is that easy and that strong.

koan
Boogity, Boogity, Boogity, Amen!

TJ 450

I'm impressed by those products... it looks ideal. 8)

It would be excellent if they were available locally.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500