I noticed this morning that my new-to-me Mercedes 300D (1981) was leaking coolant off the edge of the oil pan. After checking the forums here, I decided that it was probably due to a failed water pump, so I went and got a new one.

While removing the fan to install the water pump, I bumped the top, large coolant hose, and it came detached from the radiator. When I looked closer, I noticed that part of the cylindrical fitting on the radiator had broken off with the hose (i.e., the part that the hose is normally clamped onto). There's still about half an inch of this fitting left. (In case it's unclear, this is the top attachment point, on the driver's side of the radiator, about 1.25" in diameter.)

What I'm wondering is, can I just clamp the hose back onto the remaining stub of the radiator fitting that it normally attaches to, or would that just be asking for trouble? Or is there any way I can "rebuild" this fitting?

I'd like to avoid the expense of putting in a whole new radiator right now, but I also have a 1200-mile round-trip to make in the car next week, so I need to know I can count on it. Any suggestions?

Matthias

Unfortunately this is a common problem with these cars. If you used the search feature you would find a ton written about the radiator necks breaking off.

If you were to check a non-failed neck, you would notice a ridge that helps secure the hose. Many have tried (including myself) to repair this failure. I have had short-term luck with JBWeld, but in the end, I have had to replace it.

Some radiator shops can attach a new "top" but they are often hard to find.

Later style radiators have metal inserts inside the neck to help preventing the breaking. I have not heard exactly why they fail but some have offered: over tightening of the clamp, simply old plastic that goes through many heating ~ cooling cycles and still others have suggested the use of the dreaded green coolant.


If you are planning a 1,200 mile trip, definitely replace/repair the radiator before embarking.

You might be able to find a used one and save some money, but they sure to check the neck before purchasing.


Haasman

__________________
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)

Matthias:

This is a common problem. The same thing happened to me and if you'll search the archives you'll find a lot of information on the subject along with discussions about the most likely cause of this problem. The short of it, is crystallization of the material where the radiator hose connects.

I continued to drive my car for a few weeks after the connection failed, but the hose is subject to pop off at any time. To better secure it, I used a piece of wire that I attached to the hose clamp (I think I ran it under the hose clamp and then once around the radiator hose) and then pulled it tight and somehow attached it in front of the radiator. It has been a long time, but this is the general idea.

This is obviously not a permanent fix, but it kept the car on the road until I could order a new radiator and intall it. The only alternative to a new replacement, is to talk to a reputable radiator shop about replacing the top tank of the radiator, assuming that your radiator core is good. You'll find that some shops will do this work, but not all. Those that don't, prefer to avoid the risk of a return due to a leak. To install a new top tank, the radiator has to be removed from the vehicle and taken into the shop. You'd want to get price comparisons between a new radiator and a new tank.

I don't know if you're a DIY person, but installing a radiator is fairly easy. Do a search in the archives and you'll find info on the subject.

I hope this helps.

William

Matthias, do yourself a favor and replace the radiator ASAP, peferably before your 1,200 mile trip. A new radiator will prevent you being stranded somewhere when the temorary fix lets go. The radiator neck becomes brittle and if you glue the broken end it will fail again, likely at the most inopportune time. I replaced the radiator in our 1991 300CE after an identical experience to yours, and the repair is quite simple if you're a DIY'er ... somewhat time consuming, but straightforward and simple.

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Fred Hoelzle

A further note:

Please use only MB or Zerex G-05 coolant. It appears that the anti-corrosives in the "green" coolant both cause corrosion problems long term in iron/aluminum engines AND cause the plastic in the radiator tanks to become brittle.

I've done several of these in the last couple years.

Get a new rad pronto, DO NOT take a long trip until you do, else you will surely fail what's left of the hose nipple, and likely seriously overheat the engine. This will very likely require a complete rebuild, something you definitely want to avoid.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Thanks for all your insights, everyone. When the radiator part broke, I thought it was such a unique problem that I'd better get it up on the boards and start getting suggestions quick. Turns out, I should have checked the past posts first, since this is such a common problem.

While reviewing the boards, it looked like it might be possible to repair the broken part, with an inner copper bushing, some JB Weld, etc. But I don't want to spend the next few months wondering if my repair will suddenly fail. Your comments also let me know that the green (well, green strongly tinged with brown) color of the coolant fluid was a bad sign. I'm getting the feeling that while the previous owner changed the oil regularly, he neglected a lot of other things, like this. So I decided I was probably about due for a new radiator anyway, and ordered one from www.radiator.com. They were very friendly, had a good price ($189 for a Modine radiator), took my call on Sunday, and are delivering it directly to my door on Monday.

Wish me luck with the installation tomorrow!

P.S. Anyone have any suggestions about how to hold the water pump bearing steady while I bolt the fan back onto it? I had a hard time getting the nuts loose with my little crescent wrench, and I'm worried I won't be able to tighten them up enough when I replace it. (This whole project started with a failed waterpump.)

It has been a while since I have done one, but I recall that I left the fan belt attached and tight. I used the power steering pump pulley to turn the fan to get access to each of those little bolt heads. They do strip easily. If I recall correctly they are 10mm and a good wrench made all the difference.

Glad to hear about you going for a new radiator.

Haasman

__________________
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)

Like Haasman says. Get yourself a long good quality 10 mm wrench. Something like S&K would work. This is no place for a crescent wrench.

Peter

__________________
Auto Zentral Ltd.

Thanks for the wrench information, haasman and autozen. When you say an S&K wrench, do you mean a particular shape, or just a good quality brand? I used a brand-new Craftsman 10mm crescent/box wrench to remove the fan, which I thought would be pretty good. But the box end felt just a little loose, and chewed on the corners of the bolts a little as I tried to loosen them.

Would another brand of box wrench (e.g., S&K or maybe PowerBuilt, which I saw at the local parts store) work better, or should I switch to a different design, like the ratcheting box wrenches offered by S&K (e.g., http://www.skhandtool.com/productcatalog.cfm?tok=1)? I'm not totally sure the ratcheting wrench would fit in there, and I don't know how much difference it would make, other than minimizing the number of times I have to remove and reseat the wrench. Is there some other design I should be looking for?

Matthias, confirm that the bolts are 10mm ... try a 9mm and several English sizes to be sure. You would expect that the bolts are metric, but perhaps not. Craftsman box end wrenches/tools should be fine. I use them without any problems.

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Fred Hoelzle

I'm pretty sure they are 10mm (although they seem a little more like 9.9mm). They fit well but wiggle just a little in either end of a 10mm crescent/box wrench. They don't fit at all in a 9mm or 3/8" wrench, and they spin freely inside the opening of a 7/16" wrench. And they have metric strength numbers (8.8) on the heads.

Trust me 10mm is the size MB has used since they first went to fan clutches in the 60s. S/K is one of the better brands of hand tools for the DIY or average mechanic. There is no need to spend top $ for professional tools that you rarely use, but you don't want to pay only $15.00 for a whole set of end wrenches either. Those cheap sets are made out of hardened butter. To remove and install a fan clutch which is a job I have done coservatively speaking, about a thousand times, I use a long version snap-on open end wrench. I think Snap-On is the second best hand tool produced, but the best is Stahlwille made in Germany since about 1850. I don't advocate going out and spending about $20.00 per wrench, but don't go out and buy a piece of junk that is just going to round the corners off and make the job harder. I am not fond of Craftsman wrenches though I don't have any problem using their extensions, sockets and such. Stay away from anything that says China or Taiwan on it as far as tools go.


Peter

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Auto Zentral Ltd.

I don't know why ya'll are talking about this alledged radiator-neck-breaks-off problem.

I personally spoke to the Mercedes-Benz customer service people at the 800-number and they swore that they knew of no such problem at all. And besides, they said, if it broke at over 100,000 miles, well, what did I expect?

I said that I expected, since it was not a moving part, for it not to ever break. Then I asked if I should expect my wheels, for example, to fall apart because they also have over 100,000 miles.

I thought they were quite arrogant, actually.

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2012 E350
2006 Callaway SC560

Thanks again for your help, everyone. I'm amazed how much support there is here!

Here's what I've been up to, followed by one last question.

The new (all-metal) radiator arrived today, so I set about putting it in.

First, I finished replacing the water pump (the project that started this all). I had a hair-raising moment when I broke off one of the bolts I was using to attach it to the "housing" (the last thing between the water pump and the engine block). I was using the Haynes manual, which seemed to say to attach the water pump with 33 Nm of torque. I started thinking things were feeling a little weird around 17 Nm, and then just as I was deciding to stop at that point, one of the heads broke off. I think the Haynes manual was actually specifying the torque to attach the "housing" (whatever that is) to the main block; the Mercedes shop manual called for only 10 Nm of torque. I should have double-checked before I started!

Fortunately, when I took the water pump back off, a little bit of the bolt was sticking out and I was able to grab it with vice grips and twist it out. I was not looking forward to getting the shop to drill it out (my first thought, which they quoted at $600), or drilling it out myself (my second thought), or making another trip to the parts shop to replace the housing (my third thought).

The rest went smoothly. I went and bought new bolts to replace the tired old ones holding on the water pump and the fan. Then I had no trouble attaching either part. For the fan, I ended up using just a long 10 mm crescent wrench. I got a feel for the right torque (20-25 Nm) by turning the crescent wrench against my torque wrench untll it "popped", and then I tightened the fan bolts to what felt like the right amount. It was a lot less torque than they had originally been attached with, and with the new bolts and careful wrenching, I was able to avoid stripping anything. At this amount of torque, I could keep the fan from turning just by holding the pulley with my other hand.

Then, the radiator installation was pretty smooth, except . . . the oil cooler fittings on the new radiator seem to extend about 1/2 inch less back into the engine compartment than the ones on the original radiator. Unfortunately, the rubber hose from the transmission cooling line on the passenger side was just long enough to reach the old radiator, so now it's 1/2 inch too short to reach the new radiator. It's pretty excruciating to be so close and not able to finish the job yet. I went to Kragen and asked for a longer hose, and they said to check with Mercedes. I was surprised, because I thought this would be a pretty standardized part. I'll call the Mercedes dealership tomorrow, but if they only have hoses that are the same length, it's not going to do me much good.

Does anyone know where I should look for a custom-length rubber hose for the transmission oil cooler on short notice? I need to put it in tomorrow.

Thanks again.

I once had a similiar problem and I had to have the hoses "custom made" because the OEM versions only came in one length.

Assuming that you live in a large enough city, look in your "Yellow Pages" for "rubber specialists" or "hose and belt specialists". These are companies that cater to industrial businesses like heavy equipment. They will tell you on the phone what they can do for you or steer you to the company you need to call.

I had to take my old hoses with me and they used the end fittings to make up the new hoses to the length I specified. They fabricated the new hoses while I waited.

I hope this helps.
William