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Garage => Mechanicals => Topic started by: Jan S on 14 November 2021, 07:17 AM

Title: Thermostat housing problems - corrosion, pitting and shot threads
Post by: Jan S on 14 November 2021, 07:17 AM
Engine is 1977 US M100.985 (6.9), from a 450 SEL

I've started the job replacing the thermostat and a few cooling system hoses.

Not surprisingly, I was met by a few challenges:

Problem #1: the threads for one of the four bolts connecting the thermostat housing cover is shot (upper left thread hole), and a previous owner has solved (?) the problem by filling the threads with silicon and using a screw instead of a bolt. My goodness!

My plan is to talk to a professional workshop and see if they can fix it by inserting new threads for a smaller bolt. I guess I have one try to fix this properly. Any other suggestions?


Problem #2: the lip on the cover is severely corroded/pitted. I'm not sure to which degree this will cause a leak.

My plan is to use the thicker of the two rubber seal rings (the thermostat came with two rubber seal rings, one slightly thicker than the other). The lip on the cover plate will push the seal down and out - i.e. seal against the thermostat and the outer wall of the housing. In addition I plan to use a thin layer of sealer/silicon on the outer surface between cover and housing. I will clean all the relevant surfaces and may try some JB Weld where the pitting is unacceptable. Any suggestions/ comments?


Problem #3: the water return pipe - connected to the water pump with a hose - is severely corroded (see pic).

My plan is to clean and sand as much as possible, before I put on the new hose. How about sealing the corrosion with some Miracle Paint? Will that stop the corrosion getting worse? Any other suggestions?

(https://www.ebay.co.uk/itm/Bill-Hirsch-Miracle-Chassis-Underside-Rust-Killer-Specialist-Coating-Paint-Black-/323364698182?var=0&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338268676&toolid=10044&customid=Cj0KCQiAhMOMBhDhARIsAPVml-GfbhkR7Twxy9xQ3j-P-5ff95KZauP-opbVpSogiPnlQmREEcWw8isaAi3oEALw_wcB? 


In general - I've read some acids can remove corrosion. Any product tips and/or specs?
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: ptashek on 14 November 2021, 08:29 AM
#1 you could drill out the hole, and have a thread repair coil inserted. That's a permanent fix if done right. One issue might be finding those in aluminium.

#2 maybe time to get a replacement? Or if you know someone who can weld aluminium that'd be another route - weld the pits, and file them down flush.

Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: Alec300SD on 14 November 2021, 09:42 AM
Regarding problem #3, see my attached post for my workaround  for the damaged iron heater pipes.

http://www.peachparts.com/shopforum/4037206-post1.html

Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: PosedgeClk on 14 November 2021, 11:33 AM
Quote from: ptashek on 14 November 2021, 08:29 AM
#1 you could drill out the hole, and have a thread repair coil inserted. That's a permanent fix if done right. One issue might be finding those in aluminium.
A helicoil is a good route, and there is not any good reason to need aluminum on aluminum. You aren't passing current through this junction. A steel helicoil will work beautifully in an aluminum body.

If you wanted to spend money and make a DIY job out of it, you could use McMaster's site for reference. I would call around though and just find someone with the tooling already.

https://www.mcmaster.com/helicoils/helical-inserts-with-installation-tools-7/ (https://www.mcmaster.com/helicoils/helical-inserts-with-installation-tools-7/)
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: Jan S on 14 November 2021, 03:26 PM
Quote from: ptashek on 14 November 2021, 08:29 AM
#1 you could drill out the hole, and have a thread repair coil inserted. That's a permanent fix if done right. One issue might be finding those in aluminium.

#2 maybe time to get a replacement? Or if you know someone who can weld aluminium that'd be another route - weld the pits, and file them down flush.

#1 Yes, thread repair coil might be the way to go. I need to remove the silicon to assess the thread damage.

#2 My first thought was JB Weld, but alu welding is a good idea! I will check with a local firm that welded my rims a few years back.

Thanks!
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: Jan S on 14 November 2021, 03:40 PM
Quote from: Alec300SD on 14 November 2021, 09:42 AM
Regarding problem #3, see my attached post for my workaround  for the damaged iron heater pipes.

http://www.peachparts.com/shopforum/4037206-post1.html

Nice job! Is this the pipe for return water from heater box (under the dash) to water pump? Is it possible to disassemble this pipe without removing too many parts on engine top?

Would be great to remove it for a thorough clean and paint job.

Thanks for the advice!
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: Jan S on 14 November 2021, 03:47 PM
Quote from: PosedgeClk on 14 November 2021, 11:33 AM
Quote from: ptashek on 14 November 2021, 08:29 AM
#1 you could drill out the hole, and have a thread repair coil inserted. That's a permanent fix if done right. One issue might be finding those in aluminium.
A helicoil is a good route, and there is not any good reason to need aluminum on aluminum. You aren't passing current through this junction. A steel helicoil will work beautifully in an aluminum body.

If you wanted to spend money and make a DIY job out of it, you could use McMaster's site for reference. I would call around though and just find someone with the tooling already.

https://www.mcmaster.com/helicoils/helical-inserts-with-installation-tools-7/ (https://www.mcmaster.com/helicoils/helical-inserts-with-installation-tools-7/)

Thanks, yes I need to find someone for the repair coil job - I guess I have one try and I haven't worked with this technique before.
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: Alec300SD on 14 November 2021, 06:37 PM
Yes, that is the heater return pipe.
It was easy to remove on my 300SD with a OM617A engine
Just a couple of  8mm sheet metal screws attach the brackets on the pipe to the chassis.

Access to the mounting screws might be a little tighter in your case due to the bigger M100 engine in the engine bay.
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: TNNBENZ on 14 November 2021, 07:52 PM
Quote from: PosedgeClk on 14 November 2021, 11:33 AM
Quote from: ptashek on 14 November 2021, 08:29 AM
#1 you could drill out the hole, and have a thread repair coil inserted. That's a permanent fix if done right. One issue might be finding those in aluminium.
A helicoil is a good route, and there is not any good reason to need aluminum on aluminum. You aren't passing current through this junction. A steel helicoil will work beautifully in an aluminum body.

If you wanted to spend money and make a DIY job out of it, you could use McMaster's site for reference. I would call around though and just find someone with the tooling already.

https://www.mcmaster.com/helicoils/helical-inserts-with-installation-tools-7/ (https://www.mcmaster.com/helicoils/helical-inserts-with-installation-tools-7/)
You must be very, very careful when joining 2 different metals !!! Galvanic corrosion, or something to that effect.  Has nothing to do with electricity.  I do believe I read many times installing the wrong bolts in aluminum and it corroding the bolt & almost impossible to remove.........
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: PosedgeClk on 14 November 2021, 08:57 PM
Quote from: TNNBENZ on 14 November 2021, 07:52 PM
Has nothing to do with electricity.
It has EVERYTHING to do with electricity. The steel that they use isn't going to react with aluminum enough to matter. Find a standard potential chart, and try to make the potentials as close as possible.

Why would a steel helicoil cause corrosion when a steel screw would not?

If you pass current through this junction, more variables arise, and it is still usually not enough to matter with the currents and time scales involved in a car.
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: TNNBENZ on 15 November 2021, 09:21 AM
     All I was saying PosedgeClk is you can have corrosion without electricity.  You mentioned electricity. 
  Last night I saw another post on W116 forum that stated the same thing as I about 2 dissimilar metals.
     I agree with ptashek. I would contact a professional and at least ask if there is a corrosion possibility with a helicoil or anything with aluminum !!!
     Maybe they make aluminum helicoils.  This is why I join forums , or call professional I do not know everything...  Ha  ... lol......." I know enough 2 get me started or in trouble " ha,  lol
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: TNNBENZ on 15 November 2021, 11:05 AM
     There are many thread repair kits @ Autohauaz
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: PosedgeClk on 15 November 2021, 11:48 AM
Quote from: TNNBENZ on 15 November 2021, 09:21 AM
     All I was saying PosedgeClk is you can have corrosion without electricity.  You mentioned electricity. 
  Last night I saw another post on W116 forum that stated the same thing as I about 2 dissimilar metals.
     I agree with ptashek. I would contact a professional and at least ask if there is a corrosion possibility with a helicoil or anything with aluminum !!!
     Maybe they make aluminum helicoils.  This is why I join forums , or call professional I do not know everything...  Ha  ... lol......." I know enough 2 get me started or in trouble " ha,  lol
It's a redox reaction, so it necessarily involves electricity. The reaction itself is like the cell in a battery. The more dissimilar the metals, the higher the potential (also known as voltage) and the more rapidly that you have electrons being swapped, ions are being formed, and therefore, you have corrosion. Passing current through hastens the process. I am saying to not worry about it because there is no difference between a steel helicoil and a steel screw that was in the hole to begin with. If you are passing large amounts of current through the screw for years on end, you have to consider it. To take a ground strap as an example, the current is usually going to bypass the screw and go straight from the terminal and into the metal body because the steel of the screw has a higher resistance than the short path to the metal body. The corrosion would occur at the surface between the metal body and terminal. After many years, one would only have to sand down the terminal to shiny metal or replace the ground strap altogether.

Use a steel helicoil.
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: Jan S on 15 November 2021, 11:54 AM
Thanks to all of you for insightful and valuable comments/advice!

Still searching for a local workshop that can do the job .....

Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: Jan S on 15 November 2021, 04:04 PM
Alec300SD, too tight at the engine top - no chance in removing the return pipe (without disassembling a whole lot of stuff).

Had to sand and clean it where it sits. Put some Miracle Paint on to seal the remaining rust and stop further corrosion.

Before and after pics.
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: daantjie on 15 November 2021, 04:09 PM
Nice, necessity is the mother of invention ;)
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: Jan S on 16 November 2021, 12:26 AM
Kienle in Germany came to the rescue  :)

A nice, used part - both house and cover - is on it's way! That's better than pay the same for heli coil and welding job.
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: Jan S on 16 November 2021, 04:12 AM
Quote from: daantjie on 15 November 2021, 04:09 PM
Nice, necessity is the mother of invention ;)

Great phrase!  8)
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: TNNBENZ on 16 November 2021, 06:51 AM
Quote from: PosedgeClk on 15 November 2021, 11:48 AM
Quote from: TNNBENZ on 15 November 2021, 09:21 AM
     All I was saying PosedgeClk is you can have corrosion without electricity.  You mentioned electricity. 
  Last night I saw another post on W116 forum that stated the same thing as I about 2 dissimilar metals.
     I agree with ptashek. I would contact a professional and at least ask if there is a corrosion possibility with a helicoil or anything with aluminum !!!
     Maybe they make aluminum helicoils.  This is why I join forums , or call professional I do not know everything...  Ha  ... lol......." I know enough 2 get me started or in trouble " ha,  lol
It's a redox reaction, so it necessarily involves electricity. The reaction itself is like the cell in a battery. The more dissimilar the metals, the higher the potential (also known as voltage) and the more rapidly that you have electrons being swapped, ions are being formed, and therefore, you have corrosion. Passing current through hastens the process. I am saying to not worry about it because there is no difference between a steel helicoil and a steel screw that was in the hole to begin with. If you are passing large amounts of current through the screw for years on end, you have to consider it. To take a ground strap as an example, the current is usually going to bypass the screw and go straight from the terminal and into the metal body because the steel of the screw has a higher resistance than the short path to the metal body. The corrosion would occur at the surface between the metal body and terminal. After many years, one would only have to sand down the terminal to shiny metal or replace the ground strap altogether.

Use a steel helicoil.
10.02.2017
Which Fastener Materials Work With Aluminum Without Corroding It?

Aluminum is a lightweight, flexible and strong metal, so it's not surprising that it's so widely used for everything from aeronautics to medical equipment. However, aluminum makes it harder to choose fasteners for your project because it is so prone to reacting with other metallic substances and corroding.

Corrosion can be a deal breaker when you're planning a pressure container or a plane that will carry passengers high into the sky. A little corrosion leads to serious consequences in these cases. With the wide range of fastener materials available today, it's simply a matter of choosing one of the following options that won't corrode when in contact with aluminum.

Coated Steel

With a thick enough coating, even a very reactive metal like brass can be used on an aluminum structure without corrosion. Since stainless steel remains one of the least reactive metals without coating, it's smarter to use it as the base material. If there's any coating missing, the exposed metal still triggers less corrosion and causes fewer catastrophic failures.

There are many ways to coat steel fasteners, but most of them include a binder mixed with flakes of a noncorrosive element like zinc. For direct aluminum use, there is the option of coating the fasteners with a mixture that includes aluminum flakes specifically. This coating makes practically any fastener safe to use with aluminum as long as the coating remains intact.

It's a good idea to paint fasteners before they're installed for an extra layer that can block corrosion, but paint isn't tough enough to rely on as the only coating. Paint scrapes off during installation, so only use it as a backup technique for adding an additional layer of protection.

Electroplated Steel

One of the oldest ways of coating steel is through a process known as galvanization. It's a form of electroplating that involves adding a layer of corrosion-resistant metal onto the outside of a fastener or other component.

Since the electroplating or galvanizing technique involves electricity, it creates a very tight bond between the surface of the metal and the protective coating. However, the coating can still wear away with age or become scratched off during installation. This is why many manufacturers have switched to other coatings that have greater durability.

Electroplating remains more common than the high-tech coatings that were only recently developed. If cost is an issue, galvanized fasteners tend to cost less than coated ones while offering nearly as much corrosion resistance.

Aluminum

One type of corrosion process is known as the two-metal reaction. The presence of moisture allows an electrical connection between the two different metals, causing an exchange that leaves one of them weak and pitted. Using the same metal for all the parts of your project eliminates this problem entirely. Since there's no coating, scratches don't lead to corrosion either.

Yet aluminum is not always the best fastener material either. It doesn't offer the same strength when it comes to shearing resistance, and this is often the determining factor in choosing a fastener for a project like an airplane or a commuter train. Aluminum fasteners are usually limited to less heavy-duty uses.

Non-Metal Fasteners

Finally, fasteners made from the various high-strength plastics available today are also an option for preventing aluminum corrosion. Non-metal bolts and screws are even more limited in strength than aluminum ones, but they're still a good option for medical and food-manufacturing applications.

For most applications, a coated or galvanized steel fastener is the best option for pairing with aluminum. But the options don't stop there. Not sure which grade or type of steel you need? Give us the details of your project here at  Ascension Fasteners , and we'll help you make the right choice. ‚Äč

     I did think of a coated fastener being used but did not want 2 waste 2 much time.........
     This was written by Albert Eisenstein ( he owned a Silver/Green Metallic 450SEL )  before he died of a galvanic reaction to a shift in Uranus...
:)    :)     :)   :)     Anyway I digress...

Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: TNNBENZ on 16 November 2021, 06:52 AM
Quote from: Jan S on 16 November 2021, 12:26 AM
Kienle in Germany came to the rescue  :)

A nice, used part - both house and cover - is on it's way! That's better than pay the same for heli coil and welding job.
KOOL 4 U JanS   .   Good luck............
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: Jan S on 17 November 2021, 12:45 AM
Thanks, TNNBENZ! Great info you forwarded.

I need some luck right now ......

A minor job (replacing coolant and a few hoses) is getting bigger and bigger  >:(

First, I needed to replace the thermostat housing and cover .... now I also need to disassemble the radiator and bring it to a radiator shop (the nipple at the top broke when replacing the hose).
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: Jan S on 21 November 2021, 10:32 AM
It's worthwhile documenting cooling hose dimensions for later users (measured after removing hoses)

W116.032 US-version 1975 450 SE radiator:
- Inlet at top (from thermostat): 38 mm
- return at bottom (to water pump): 38 mm
- inlet from reservoir tank (at the bottom): 18 mm
- nipple at the top (return to reservoir tank): 8 mm

Engine 100.985 6.9 1977 US-version:
- Inlet water pump (from radiator): 42 mm
- short hose between engine and thermostat housing: 42 mm (length approx 38 mm)
- hose between return pipe heater box and water pump: 18 mm
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: TNNBENZ on 23 November 2021, 12:03 PM
Quote from: Jan S on 17 November 2021, 12:45 AM
Thanks, TNNBENZ! Great info you forwarded.

I need some luck right now ......

A minor job (replacing coolant and a few hoses) is getting bigger and bigger  >:(

First, I needed to replace the thermostat housing and cover .... now I also need to disassemble the radiator and bring it to a radiator shop (the nipple at the top broke when replacing the hose).
Is this common, the inlet breaking when removing the rad. hose ?   I seem to recall a few post reporting this happening to them also.    ???  :( :(   :-[
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: TNNBENZ on 23 November 2021, 12:17 PM
Quote from: Jan S on 14 November 2021, 03:40 PM
Quote from: Alec300SD on 14 November 2021, 09:42 AM
Regarding problem #3, see my attached post for my workaround  for the damaged iron heater pipes.

http://www.peachparts.com/shopforum/4037206-post1.html

Nice job! Is this the pipe for return water from heater box (under the dash) to water pump? Is it possible to disassemble this pipe without removing too many parts on engine top?

Would be great to remove it for a thorough clean and paint job.

Thanks for the advice!
Where is the key/name for the numbers in the diagram ?  Is this the parts manual that has no explanation to the numbers.
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: Jan S on 23 November 2021, 02:45 PM
You click on the part number e.g. 405 and are directed further down on that same page to the part OEM number and name.

See link

http://www.catcar.info/mercedes/?lang=en&l=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

Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: Jan S on 23 November 2021, 02:55 PM
Quote from: TNNBENZ on 23 November 2021, 12:03 PM
Quote from: Jan S on 17 November 2021, 12:45 AM
Thanks, TNNBENZ! Great info you forwarded.

I need some luck right now ......

A minor job (replacing coolant and a few hoses) is getting bigger and bigger  >:(

First, I needed to replace the thermostat housing and cover .... now I also need to disassemble the radiator and bring it to a radiator shop (the nipple at the top broke when replacing the hose).
Is this common, the inlet breaking when removing the rad. hose ?   I seem to recall a few post reporting this happening to them also.    ???  :( :(   :-[

I delivered the entire radiator to a radiator workshop for a total rehab incl. new core. It was time .... 46 years.

The guy at the shop confirmed this happens all the time, the nipple gets brittle and a small touch is enough.

Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: TNNBENZ on 23 November 2021, 07:29 PM
Quote from: Jan S on 23 November 2021, 02:45 PM
You click on the part number e.g. 405 and are directed further down on that same page to the part OEM number and name.

See link

http://www.catcar.info/mercedes/?lang=en&l=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
I was referring to a small book I bought, Black, rectangular with pages of parts with numbers, your diagram looks exactly like a page from my book, only my book has no part names 2 go with the numbers !!!!!  :(  ???   >:(
     The link u posted appears 2 b amazing.........Thank-you... :)
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: Jan S on 03 December 2021, 02:08 PM
Yes, a great source, I use it a lot!
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: Jan S on 23 December 2021, 07:42 AM
A few days ago I picked up my fully renovated radiator -- It has been disassembled into individual parts, sandblasted, new core, tubes/nipples/flanges refitted, painted and pressure tested. Looks great!

I want to assemble it all in my non-heated garage next week, despite outdoor temperatures of -12 deg C (10 deg F). I look forward to it  :(

- new radiator
- new hoses (some seen in the pic)
- new thermostat housing incl. new cover with new bolts and new gaskets
- new thermostat
- new coolant
- cleaned and polished aux air valve (AAV)

If everything goes to plan I will be able to adjust idle to 600 rpm (coolant temp of 90 deg C and fully closed AAV).
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: rumb on 23 December 2021, 10:55 AM
Looking good!
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: Jan S 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?
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: daantjie 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.
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: Jan S 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.
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: Jan S 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.
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: daantjie on 06 January 2022, 04:05 PM
Quote from: Jan S 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.

Nicely done  ;)
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: Jan S 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")
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: rumb 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
Title: Re: Thermostat housing problems - corrosion, pitting and shot threads
Post by: Jan S 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?