Thermostat housing problems - corrosion, pitting and shot threads

Started by Jan S, 14 November 2021, 07:17 AM

daantjie

Daniel
1977 450 SEL 6.9 - Astralsilber

Jan S

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.
1975-mod W116 450 SE with 6.9 engine

Jan S

1975-mod W116 450 SE with 6.9 engine

TNNBENZ

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...

Neglected ~ Rescued ~ 1977 450SEL 4.5L  U.S.A. ver.
Project of Compassion ~ Respect
Silver Green Metallic / Toast
Left Hand Drive
Sliding Roof

TNNBENZ

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............
Neglected ~ Rescued ~ 1977 450SEL 4.5L  U.S.A. ver.
Project of Compassion ~ Respect
Silver Green Metallic / Toast
Left Hand Drive
Sliding Roof

Jan S

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).
1975-mod W116 450 SE with 6.9 engine

Jan S

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
1975-mod W116 450 SE with 6.9 engine

TNNBENZ

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.    ???  :( :(   :-[
Neglected ~ Rescued ~ 1977 450SEL 4.5L  U.S.A. ver.
Project of Compassion ~ Respect
Silver Green Metallic / Toast
Left Hand Drive
Sliding Roof

TNNBENZ

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.
Neglected ~ Rescued ~ 1977 450SEL 4.5L  U.S.A. ver.
Project of Compassion ~ Respect
Silver Green Metallic / Toast
Left Hand Drive
Sliding Roof


Jan S

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.

1975-mod W116 450 SE with 6.9 engine

TNNBENZ

Neglected ~ Rescued ~ 1977 450SEL 4.5L  U.S.A. ver.
Project of Compassion ~ Respect
Silver Green Metallic / Toast
Left Hand Drive
Sliding Roof

Jan S

1975-mod W116 450 SE with 6.9 engine

Jan S

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).
1975-mod W116 450 SE with 6.9 engine

rumb

'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550, '16 AMG GTS