Stuck (learn from my mistake) - PeachParts Mercedes-Benz Forum

tbomachines · #1 08-16-2009, 01:22 PM

Last week I flushed the coolant in Boxy (1982 300SD) and had great initial results - much better cooling performance, less temp variation, etc. Got to work last Thursday and saw a small leak on the upper radiator hose. No biggie, I think...must not have tightened the clamp enough and of course, the clamp was a bit loose. So I tighten it down, not thinking much about it. That night, I drive down from CT to PA (I do this regularly) with no problems as far as I could tell. Spend the night, etc. Then, Friday comes around with its 90 degrees

and I notice coolant dripping pretty quickly from the upper hose. Just tightening it, I wasn't sure what it was, but it was a bit loose again so I tighten...and it begins to gush out. I quickly/carefully released the pressure by the cap to get it to stop gushing....let it cool down and I take off the upper hose.

The upper radiator neck had snapped clean off

. I had to fish the end out of the hose. My fears were confirmed when I jumped on here to see if just the upper neck was replaceable and indeed it isn't - I will be ordering a new radiator. For now, I've JB-welded the neck back on, about to give it another coat of JB to stop any pinholes. Obviously just a temporary fix that should just get me around town if I need it. Anyone used JB-weld on a radiator neck before?

Now, the lesson:
DO NOT OVER TIGHTEN YOUR RADIATOR HOSE CLAMPS!!!

Or fear the wrath of being stuck in one place and spending lots of money!

pawoSD · #2 08-16-2009, 01:27 PM

I think I'd be careful with that JB-welded fix....its likely not going to last.

I have yet to see a radiator neck fail in my own experiences....my car had the original radiator up until about 2-3 years ago, and it never failed.....it ended up leaking from the tanks/seam. I bought a new Behr unit....and its been great.

It lowered my hot-day temps significantly too.....now it never gets over 85C or so.....it used to climb to 95-100 on hot days idling. I switched to the plastic fan too....much more air flow.

JimFreeh · #3 08-16-2009, 01:28 PM

I've seen a metal sleeve inside the plastic pipe, and I've also seen the rubber hose clamped onto the remainder of the hose outlet.

By turning the radiator cap slightly, you can relieve the pressure and buy a little time.

Ultimately, a new or replacement radiator is needed.

Jim

lietuviai · #4 08-16-2009, 02:00 PM

I broke an upper neck once by just trying to remove the radiator hose. I think the plastic tank design is a terrible one, especially in a car that cost over $30K when new.

Jeremy5848 · #5 08-16-2009, 02:33 PM

The early radiators had a plastic-only neck. My '85 does and my mechanic pointed it out and added a second clamp so that each of the two could be tightened less than one clamp alone.

Later radiators have a metal sleeve inside the plastic to prevent the problem that Boxy just had. I've looked into installing my own liner but the plastic doesn't have parallel sides on the inside. It might be possible to use a sealer to fill the gap but I never got around to trying and so far (3 years) the radiator has survived.

Jeremy

Matt L · #6 08-16-2009, 02:42 PM

I wouldn't use any sealer on the inside, especially on the radiator outlet. A chunk could come loose and cause trouble.

tbomachines · #7 08-17-2009, 09:02 AM

Thanks for the info guys. I went out and checked on it this morning and it actually looks pretty good. The grab-it-and-yank stress test didn't budge the JB, I imagine the force I used probably would have broken the plastic alone. After all is said and done, there is about 1/8 inch coating of JB inside and outside of the neck, which dried very smooth. My only concern is that there may be tiny plastic pieces floating around that could potentially damage the water pump and/or thermostat. The break was very clean however, I was able to piece it back together like a puzzle, so no major pieces floating anywhere. Desperate times call for desperate measures and I'm thinking this is a desperate time!! Perfect day to test my temporary fix - 95 degrees. I'll update soon, just ordered a radiator overnighted from PeachParts and I found out there's an indy specializing in mercedes about a block away from my place.

TX76513 · #8 08-17-2009, 09:14 AM

You didn't say which JB product you use - the standard JB doesn't give a permanent hold to ABS plastic. They do make a product called Water Weld that does..

LUVMBDiesels · #9 08-17-2009, 10:10 AM

I think either Fastlane or Diesel Giant sells the metal insert.

moon161 · #10 08-17-2009, 10:18 AM

Unspeakable *************** sells an insert.

tbomachines · #11 08-17-2009, 10:21 AM

I think water weld is as an underwater epoxy, regular JB (which is what I used) should hold up okay since I allowed it to cure in a dry environment. In this case, the plastic is fairly porous, I made sure that it bonded to it before I went crazy and gooped the whole thing. I'll admit though I probably would have used water weld if I knew about it. I'd like to recommend the metal sleeve to anyone with an original radiator, its cheap insurance. Also, Pawo's suggestion about using 2 clamps is a great one as well!

tbomachines · #12 08-17-2009, 12:57 PM

Just started it up and ran it for 15 minutes or so - no leaks at all, gives me a little reassurance. Not going to drive it too much, but it looks like it will hold up well until I get the new radiator in.