Removing t-stat housing on OM616 w/ York compressor - PeachParts Mercedes-Benz Forum

BodhiBenz1987 · #1 06-23-2011, 09:17 PM

Something in the vicinity of the thermostat housing is drooling coolant down the block of my '78 240D, and I figured the first step should be remove the housing and replace the gasket and short water pump hose, or at least get a better look at where the leak is coming from. Can it be done without removing the York compressor? I'm not really sure where to start, because there are bolts on both the housing and compressor that look impossible to reach with the other unit in way. Or can I just remove the entire compressor bracket, with the compressor still on it? That would allow me a better look at the water pump too, which I haven't entirely ruled out.
Also, I've read conflicting posts via search as to whether to use a sealant on the gasket between the t-stat housing and head ... should I use Permatex in addition to the new gasket, or just the gasket?

leathermang · #2 06-23-2011, 09:25 PM

What is the gasket made of ?
If some fiber or paper... I coat mine with the thinnest coat of RTV and let cure overnight... both sides.... then when putting together another wiped on thin coat....and install to proper torque... over torquing is the number one reason any gaskets fail...

rs899 · #3 06-23-2011, 09:38 PM

I did something like this on my '77 240D some time ago. IIRC I was able to loosen the compressor bracket enough to change the water pump, so I think you can get to everything that way. It wasn't the easiest thing and a few assorted curse words needed to be uttered.

BodhiBenz1987 · #4 06-23-2011, 11:39 PM

It's a thin papery-type material. Any chance you know the torque figures? One of these days I should hunt down an FSM for this car, I suppose. The Haynes manual does not have a lot of the specs.
rs899, thanks, I'll see if loosening the bracket works. I will have plenty of curse phrases on hand in case I need them.

kerry · #5 06-23-2011, 11:43 PM

I ground away a portion of the compressor bracket on my 77 300d with a dremel tool in order to access one bolt to replace the water pump without loosening the bracket.

otto huber · #6 06-24-2011, 03:54 AM

I'm surprised that you said it was a paper gasket. Have you checked what is already in the thermostat housing now? I used to own a '78, and a '79, and both had an o-ring which fit into a groove and no sealant was necessary. The o-ring came with the thermostat.

leathermang · #7 06-24-2011, 07:48 AM

Otto, if you are directing that to me..... I did not say it IS a paper or fiber gasket... I said that is how I would treat it if it was... if he is lucky it will be the much nicer thought out seal which you describe.
On water holding gaskets I avoid the aviation gasket type cements because they are so much trouble to clean up to reinstall.

tangofox007 · #8 06-24-2011, 07:56 AM

Quote:

Originally Posted by otto huber

I used to own a '78, and a '79, and both had an o-ring which fit into a groove and no sealant was necessary. The o-ring came with the thermostat.

The thermostat gasket and the thermostat housing gasket are two different animals. The question regarded the latter.

Quote:

Originally Posted by otto huber

I'm surprised that you said it was a paper gasket.

Once in a while, you do find a post on here with the correct information. Surprising as that might be.

http://catalog.peachparts.com/ShopByVehicle.epc?q=1978-Mercedes--Benz-240d-Cooling--System&yearid=1978%40%401978&makeid=63%40%40MERCEDES+BENZ%40%40X&modelid=6138%3AED%7C10000129%3AMBC%7C1489%40%40240D&catid=240909%40%40Cooling+System&subcatid=240986@@Thermostat+Housing+Gskt%2E&mode=PD

tangofox007 · #9 06-24-2011, 08:16 AM

Quote:

Originally Posted by BodhiBenz1987

It's a thin papery-type material. Any chance you know the torque figures?

I checked the 617 FSM, which has an identical arrangement. It the torques values are there, I didn't see them.

Quote:

Originally Posted by BodhiBenz1987

Also, I've read conflicting posts via search as to whether to use a sealant on the gasket between the t-stat housing and head ... should I use Permatex in addition to the new gasket, or just the gasket?

"Permatex" includes a wide range of possibilities. I would suggest a non-hardening variety, like Permatex #2 or, better yet:
http://www.permatex.com/products/Automotive/automotive_gasketing/gasket_makers/Permatex_Water_Pump_Thermostat_RTV_Silicone_Gasket.htm

otto huber · #10 06-24-2011, 01:19 PM

[QUOTE=tangofox007;2740836]The thermostat gasket and the thermostat housing gasket are two different animals. The question regarded the latter.

LOL, this is what happens when I log in at 1:00 A.M.

I've replaced the gasket that the OP is referring to, and I had success without using a sealant. I remember that the gasket was not paper.

BodhiBenz1987 · #11 06-25-2011, 01:39 AM

After worrying about my other car for a while, I made an attempt to get the housing off this evening and rs899 was certainly right about curse words being needed. All I achieved was discovering that getting the compressor bracket off is going to require removing the pulley on the water pump, because two bolts are behind it. I managed to get one bolt off the t-stat housing with the bracket in place, but couldn't get to the other one for the life of me. If I could remove the top bolt, maybe I could get a wrench down there, but (you guessed it) you can't remove the top bolt because the AC bracket is in the way.

There's actually a hole in the bracket to access the hose clamps, so if I could only get that one bolt ...

rs899 · #12 06-25-2011, 06:58 AM

Quote:

I ground away a portion of the compressor bracket on my 77 300d with a dremel tool in order to access one bolt to replace the water pump without loosening the bracket.

^^what Kerry did. I don't recall doing this. Perhaps I removed or loosened the compressor from/on the bracket? Does that make any sense? Wasn't fun. They obviously didn't originally design this engine with A/C in mind.

Rick

BodhiBenz1987 · #13 10-22-2011, 08:14 PM

Ressurrecting this with a new question. I finally got about to finishing this, which involved removing the fan pulley and A/C compressor, of course, buttoned it all back up and tested it w/ a pressure tester I rented. Coolant and air bubbled out the housing/block union.

So, took it apart and took another look and found some pitting on the mating surface of the housing. I was thinking about using JB weld to fill the slight pit and sanding it flush, then trying again. I did use Permatex water pump gasket maker the first try (in addition to paper gasket), though I could also try just using more Permatex to fill the pitting. Thoughts? I'm not too keen on having to do this job a third time, so trying to get it right this time!