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  #1  
Old 01-29-2014, 04:59 PM
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Thermostat housing corrosion

I pulled the thermostat housing off my 83 617.952 to replace the small hose that connects it to the water pump housing outlet.

I found sever corrosion on the nipples of the aluminum, it's strange this corrosion is ONLY on the side that had contact with the hose, the inner surface is smooth as can be, though discolored by some rust.

I'm guessing the PO didn't use the correct coolant, or for that matter maybe just straight water at some point.

The question is, I'm not sure the new hose is going to provide a good seal with this level of and depth of pitting. Can I repair it with JB Marine Weld? It claims to be specific for this kind of repair, and specifies aluminum.

Thoughts?

Thanks

Attached Thumbnails
Thermostat housing corrosion-sam_0160.jpg   Thermostat housing corrosion-sam_0157.jpg  
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  #2  
Old 01-29-2014, 05:07 PM
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JB Weld will probably work IF you can get everything clean enough. I cut off the piece that the heater hose slides over and nipped the "bump" off that would prevent a hose from sliding further down the fitting. There may be a pic in my build thread. If you need a pic I'll post it.

Anyhow, that fixed the heater hose fitting - mine was actually perforated under the hose. I'll wager that you're right on the coolant selection. I'll be running water w/water wetter as required by the track in the event of a loss of coolant on the track. Not sure what to do about the electrolysis except to run distilled water. Of course this means draining the system every fall but I'm used to that.

Dan
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  #3  
Old 01-29-2014, 05:49 PM
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You could run NPG as I do in my signature car. No corrosion, no electrolysis, no cavitation, and it boils at 370* so you can run at zero pressure.
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Old 01-29-2014, 06:23 PM
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The corrosion is always on the outside because of the air interface oxidation. There probably was a ongoing slight leak which corrodes the outside when it meets air, similar to the oxidation of copper pipe. There is nothing to do with the coolant, red or green.

Sand down the corroded part well, JB weld and sand down surface again. It should be good to go for the next 200K miles.
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  #5  
Old 01-29-2014, 06:27 PM
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Quote:
Originally Posted by ah-kay View Post
The corrosion is always on the outside because of the air interface oxidation. There probably was a ongoing slight leak which corrodes the outside when it meets air, similar to the oxidation of copper pipe. There is nothing to do with the coolant, red or green.

Sand down the corroded part well, JB weld and sand down surface again. It should be good to go for the next 200K miles.
+1. Wouldn't hurt to smear some grease on it before putting the hose on to slow down corrosion.
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  #6  
Old 01-29-2014, 06:42 PM
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This tends to occur on cars with weak coolant rather than the "wrong" coolant.

Weak coolant is trapped in the void between the aluminum and unclamped portion of the hose. Corrosion grows under the clamped portion causing an eventual leak.

Epoxy will work but you must get the surface completely clean ( sand blast / wire brush ) , a more direct route is to replace the housing. The hose (s) should be replaced as well, the rubber will have gotten pretty rough and squished out by now.

Grease won't help and can cause slippage of the hose under pressure.
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  #7  
Old 01-29-2014, 07:07 PM
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I had the same problem.
I scarped the Holes down to the bare Metal and filled the hole with JB Weld epoxy the one that can take up to 250 degrees (not the Fast set Epoxy) and I wrapped tape over the Epoxy and around the Nipple to hold the Epoxy in and make the surface as round as possible.

After the Epoxy cured I filed off the excess and filled in what ever holes there were that did not get filled.

That was close to 5 Years ago with no leaks.
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Old 01-29-2014, 08:37 PM
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Quote:
Originally Posted by 97 SL320 View Post
This tends to occur on cars with weak coolant rather than the "wrong" coolant.

Weak coolant is trapped in the void between the aluminum and unclamped portion of the hose. Corrosion grows under the clamped portion causing an eventual leak.

Epoxy will work but you must get the surface completely clean ( sand blast / wire brush ) , a more direct route is to replace the housing. The hose (s) should be replaced as well, the rubber will have gotten pretty rough and squished out by now.

Grease won't help and can cause slippage of the hose under pressure.
I agree with you after taking a closer look at the PO's pics, where most of the corrosion is on the coolant side of the clamp. I have put a light film of grease on coolant nipples and never had a hose slip off under pressure.
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  #9  
Old 02-02-2014, 11:44 AM
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Repaired parts.

Here's what I ended up with using JB Weld Marine. I chose the Marine product because it said specifically that aluminum was compatible, and that it was good for water applications.

I think these will get me a 100,000 miles further...
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Thermostat housing corrosion-sam_0167.jpg   Thermostat housing corrosion-sam_0172.jpg  
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  #10  
Old 02-02-2014, 11:57 AM
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Originally Posted by rscurtis View Post
You could run NPG as I do in my signature car. No corrosion, no electrolysis, no cavitation, and it boils at 370* so you can run at zero pressure.
I second that. As far as I know, the only product available is Evan's Waterless Coolant (search). I put their NPG+ in my 85 300D. If it works OK thru the summer, I will start putting it in my other cars. Costs 4x regular coolant, but lasts forever and no more corrosion, nor pressure in the cooling system. M-B parts are so expensive and hard to change, the payback is quick.
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  #11  
Old 02-02-2014, 12:19 PM
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I've never heard of this NPG stuff before, can you guys tell me more? It's really not much more expensive than the MB coolant to be honest.
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  #12  
Old 02-02-2014, 04:32 PM
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I had the same cavitation when I got my 84 last summer. Did the whole JB repair, it lasted 1 month. I would suggest you get another goose neck. Not expensive, and just better insurance.
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  #13  
Old 02-02-2014, 04:48 PM
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Originally Posted by lespigpen View Post
I had the same cavitation when I got my 84 last summer. Did the whole JB repair, it lasted 1 month. I would suggest you get another goose neck. Not expensive, and just better insurance.
Now ya tell me ;-)

Where does one find this part, our hosts here don't sell it, so would it violate the rules to point someone in the right direction?
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Last edited by crazy4diesel; 02-02-2014 at 04:59 PM.
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  #14  
Old 02-02-2014, 07:52 PM
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They do sell them if you search for the part number:

A bit rich for me...

Thermostat housing

I just picked one up today at the junk yard. Pretty good shape, for under $6. But it will be hit and miss. One you pull may end up looking like yours too.
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  #15  
Old 02-02-2014, 07:55 PM
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I have a good used one. pm if anyone is interested.

Quote:
Originally Posted by uberwasser View Post
They do sell them if you search for the part number:

A bit rich for me...

Thermostat housing

I just picked one up today at the junk yard. Pretty good shape, for under $6. But it will be hit and miss. One you pull may end up looking like yours too.

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