W123 Coolant (Bypass?) Hose Replacement
 

I've searched around but not knowing the correct name for this hose is netting me little in results.

What I'm referring to is the approximately 3" long coolant hose, about 1.5" in diameter. It connects the water pump to the thermostat housing (I believe the thermostat is in there) on the front of the engine.

Anyhow, what I'm trying to figure out is how much cussing will it take to replace that hose? At first I thought it was a two minute job but upon closer inspection it appears that I will need to remove the water pump as the thermostat housing seems to be cast right into the head.

Someone else must have experience with this, I can take a picture if my description is insufficient.

Thanks!

not sure on the OM616 but on the OM617 you can remove the whole thermostat housing (the top of the bypass hose connects to it there); three screws if i remember correctly mounted to the side of the head

Thanks!

I probably just need to take a closer look, that would be a very strange (if not impossible) casting so there is probably a seam I missed.

The first thing to try is tightening the clamps. These hoses are very high quality from the factory and do not need replacing all that often. If that does not work you may be able to get it out without removing the stat housing. The old hose can be cut if necessary to get it out and you may be able to wiggle and fold the new one to get it in.

I have had at least 30 old benzes and cannot remember for sure about how to replace this hose so that gives you an idea how seldom they go bad.

I just replaced that on my SD.

I removed the two bolts holding the the part to the engine (no gasket), removed the hose, got a foot of 1 5/8 inch hose from the local auto zoo, cut to fit, installed a gasket, bolted everything back up, no problems.

The thermostat housing bolts up to the block on your OM616 just like the OM617. I took the housing off when I got my 240d because I had a leak there as well and found out that the part where the housing fits up to the short heater hose was broken. I too got a piece of heater hose from the local auto parts store and cut it to the proper length. I didn't/don't have a gasket between the housing and the block either and it doesn't leak there. For some reason, I thought I remember seeing a gasket in the parts diagram at the dealer parts dept.

After all this, my new hose still leaks which I attribute to my broken housing. How bad is the hose? Maybe tightening the two hose clamps will fix the leak.

That is only gong to happen in a story that begins with "Once upon a time..."

I used gas tank filler hose 1-5/8" SUPER thick rubber, with cloth reinforcement. very good stuff.

That's where I got the part numbers and ordered everything. You don't need the t'stat gasket and those three screws are not relevant to my car, oh well. I'll eventually use the t'stat gasket and the extra screws aren't a big deal. All the parts except for the hose arrived quickly. I finally ran out of time waiting for the section ($35.00! Are you kidding me? Someone is putting their kid through college.) hose, so I took the old one and found a suitable replacement.

Uploads aren't working right now, my old hose has a split.

Wow, that was all the info I needed and then some. This forum never ceases to amaze me.

Thanks for all the help everyone!

Thermostat bypass hose, ***************, https://www.***************/search/product.asp
 

Thermostat bypass hose, ********az,

https://www.***************/search/product.aspx?sid=zidlbafu0oqubc55zje2az55&partnumber=900271-042012

Older thread, newer bump. Noticed I needed one of these after performing a diesel purge. I opted to get a 4 ply straight silicon hose, with stainless steel braid reinforcement, like the kind used for turbo intercoolers. They are sold on eBay for cheap, and come pre-cut to about 3 inches in length, which you can cut down to 2" using an angle grinder or pipe cutter.

Anyway thanks to all those providing info on this thread

http://i.ebayimg.com/00/s/MTA4MlgxMj...TGSjy/$_57.JPG

Sev,
Thanks for posting this. I also was going to suggest silicone hose. I used that on my 64 Valiant slant six engine for its short bypass hose (5/8"D), and the silicone let me easily work it into that small gap, plus should last forever. I used much larger silicone hose (2.5"D?) for the turbo inlet on my 1985 CA 300D. Same on my 1984 300D, installing a 1985 CA frame-mounted air cleaner. It comes blue & red, if you want a purty engine. It cuts easy w/ a cheap razor knife.

Coolant by-pass
 

http://www.peachparts.com/shopforum/...1&d=1433192114
Red Alert! Two weeks ago I started to replace my by-pass hose. After twisting off both bolts (and I was gentle) I still don't have my car running. Use caution removing the bolts, there isn't enough penetrating fluid on the planet to dissolve the oxidation and crud. I might add if the bolts don't break free immediately, re-think it. I wish I would have left it alone.