Author Topic: Thermostat housing problems - corrosion, pitting and shot threads  (Read 1072 times)

Jan S

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Re: Thermostat housing problems - corrosion, pitting and shot threads
« Reply #30 on: 02 January 2022, 08:59 AM »
Problem?

I'm replacing the old coolant hose between engine and thermostat housing (see pic with housing and new hose). The hose is 42 mm diameter and 38 mm length. Fairly stiff.

The old hose (see second pic) has a bulge in the middle, probably to allow for thermal expansion/contraction between engine block and water pump housing/ thermostat housing.

What do you think? Will there be a problem with the "stiff" new hose? Any experience with this? Does current OEM hoses have this bulge?
1975-mod W116 450 SE with 6.9 engine

daantjie

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Re: Thermostat housing problems - corrosion, pitting and shot threads
« Reply #31 on: 02 January 2022, 09:19 AM »
Mine was exactly the same with the bulge on the old hose.  I think it's a function of multiple expansion cycles and the hose clamps on either end.
The new hose as you show it is good as is.
Daniel
1977 450 SEL 6.9 - Astralsilber

Jan S

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Re: Thermostat housing problems - corrosion, pitting and shot threads
« Reply #32 on: 03 January 2022, 02:33 AM »
Good point. I thought the hose had a bulge designed into it (i see on www that you can buy certain hoses with a bulge .... but not 42 mm  :-\ )

As you say - the cycles literally work their way into the rubber hose.
1975-mod W116 450 SE with 6.9 engine

Jan S

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Re: Thermostat housing problems - corrosion, pitting and shot threads
« Reply #33 on: 06 January 2022, 12:58 PM »
Working on the car in a non heated garage at -10 deg C/ 14 deg F is fun! Hard to move around with several layers of wool and a thermo suit on top  :)

Today I managed to assemble:

- new thermostat housing, new cover, new 4 x bolts, new gasket, new thermostat
- new hose from heater return to water pump incl. 2 x new clamps
- new hose between engine and thermostat housing incl. 2 x new clamps

Renovated radiator and the rest of the hoses will be assembled at the weekend, followed by idle rpm adjustments and ignition timing check.
1975-mod W116 450 SE with 6.9 engine

daantjie

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Re: Thermostat housing problems - corrosion, pitting and shot threads
« Reply #34 on: 06 January 2022, 04:05 PM »
Working on the car in a non heated garage at -10 deg C/ 14 deg F is fun! Hard to move around with several layers of wool and a thermo suit on top  :)

Today I managed to assemble:

- new thermostat housing, new cover, new 4 x bolts, new gasket, new thermostat
- new hose from heater return to water pump incl. 2 x new clamps
- new hose between engine and thermostat housing incl. 2 x new clamps

Renovated radiator and the rest of the hoses will be assembled at the weekend, followed by idle rpm adjustments and ignition timing check.

Nicely done  ;)
Daniel
1977 450 SEL 6.9 - Astralsilber

Jan S

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Re: Thermostat housing problems - corrosion, pitting and shot threads
« Reply #35 on: 09 January 2022, 09:29 AM »
All new/renovated parts have been assembled (radiator, hoses, thermostat, thermostat housing, etc.) and new coolant has been added (50-50 Comma antifreeze and demineralized water)

Engine started immediately (hasn't run since oct/nov). Always a good sign ;D.

A few problems surfaced:

- a minor coolant leak at the flange between thermostat housing and water pump housing. I regret not adding silicon sealant under/over the self-made seal. I need to fix that later in spring

- The oil/ATF connections at the radiator have minor leaks. The work shop that renovated the radiator also painted the threads on the nipple (they shouldn't have done this!), which makes it really hard to tighten the nut ... I need to tighten a bit more, hopefully the nipple remains in place.

- Although the thermostat is new the coolant doesn't reach the correct temperature when engine is warm (see a different post: "6.9 K-jetronic rough and high idle cold start")
1975-mod W116 450 SE with 6.9 engine

rumb

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Re: Thermostat housing problems - corrosion, pitting and shot threads
« Reply #36 on: 09 January 2022, 11:02 AM »
I would clean the nipple/threads with a wire brush and use a second wrench on it.  It's too easy to twist it off otherwise.  - been there and done that!  :o
'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

Jan S

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Re: Thermostat housing problems - corrosion, pitting and shot threads
« Reply #37 on: 09 January 2022, 11:50 AM »
Thanks for the tip, rumb!

Yes, I have a wire brush somewhere .....

You mean a second wrench 180 deg to the other wrench?
1975-mod W116 450 SE with 6.9 engine