I have a small crack in area of upper hose connection. The crack is 3/8" long and on top and easily accessible between hose and radiator tank, but can not be covered by hose because of tank molding. Has anyone tried to repair or know type of plastic material that MB uses in the construction of the radiators found in 92 500SL. The purchase of a new radiator seems excessively expensive considering the size of leak.

Happened to me on my 1990 300SE except the failure was catastrophic - neck broke off and coolant spilled all over the place.

You can try to reinforce the neck with a piece of copper tubing if you can find one that fits snugly and use some high-temp epoxy like JB Weld.

There is a description of the problem and a repair kit at: http://www.**************.com/. It is in the section called 'Maintenance Alerts'.

Many threads on this problem here - a $200 radiator makes the problem go away for a long time. The wiki section has a replacement guide.

Thanks rickpark for responding. The use of a tube to reinforce neck as preventive measure makes alot of sense. I have considered using a copper sink drain pipe used for traps and install inside the neck but only size available is 1.5 od, similar to od of neck pipe. May work if split longitudinally to leave a gap to adjust od and locate gap opposite to existing crack then collapse od to fit. Type of plastic used by Behr/MB still a factor to consider when using adhesives and, hopefully, someone on forum has this knowledge. Super glue would probably work but it sets so fast and is so permanent I am afraid to use it.

Don, your problem involves a risk/reward philosophy. A Rube Goldberg fix may work indefinitely, or when/if the radiator upper hose connection separates from the radiator at highway speeds you may be facing extensive engine damage/repair. I understand your reluctance to replace the radiator ... at $500 online that's reason to pause; however, peace of mind is priceless. The upper hose connection on our 1991 300CE developed a circumferential crack and came apart while my wife was parking the car. The remaining stub was long enough to accept the radiator hose so I could drive the car a short distance home ... replaced the radiator before driving the car again. It's an easy DIY job on a 300CE ... probably a bear of a job on a 500SL.

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Fred Hoelzle

My 300SE radiator was around $200 but obviously a different car and radiator.

And the R&R procedures are likely very different.

If you do try the neck reinforcement approach, assess the condition of the plastic carefully as the crack may be indicative of rotting of the plastic which would make any repair strictly temporary.

Also make sure your choice of adhesive is rated for the expected operating temperature and make sure both the neck and the reinforcement piece are clean, dry and well roughened to give the adhesive something to bond to.

read the posts and felt had to post.what you are all missing is this.mercedes radiators are made of plastic and aluminium and as they age[6-8yrs]two things happen.1 the plastic petrifies[meaning that when you fix a hole a new one will arise to take it's place].2 over temperature cycles the aluminium core will shrink and cut down on the quantity of water moving through the tubes.a classic case of this is sitting at idle foot on brake car in drive ac on and temp starts to rise but when you hit the gas and take off[speeding up engine and therefore water pump]you can watch the gauge drop.if you dont want to be constantly fixing the cooling system and maybe an engine bite the bullet and buy a new radiator. david poole owner european performance dallas texas

Appreciate all responses and intent. I am not trying to be cheap by not purchasing a new radiator to fix problem but I am a believer that new is not always better. Apparently current economical conditions are causing a relaxation of effort in regard to quality control. If part is frequently subject to failure, it would seem wise to look for a solution or remedy before replacing the part with a new same defective part. The plastic neck is not deteriating or about to break off. As I attempted to explain in my description of crack: it is about 1/4" to 3/8" (8 to 12mm) long, on top of neck between hose and radiator, longitudinal in direction, and leaks very little when hot. My thinking was, if the plastic can be sealed to the aluminum, there must be an adhesive or heat involved (maybe both) and the same process can be used to seal a small crack. I suspect that the crack was caused by someone or mechanic that leaned on the part with possibly an elbow. I have requested Behr provide me with information as to type of plastic used but, no response as of this date.

Don, the hose connections on the new radiators are reinforced with a metal insert ... at least on the new Behr radiator I bought for our 300CE. For whatever reason I noticed online that while a new Behr radiator for your 500SL costs $500, a new radiator for a 300CE costs less than $200. The difficulty in repairing the crack is getting the mating surfaces clean enough for an adhesive to hold ... that's assuming there is no way to clamp a patch over the crack. Even a dab of some super adhesive atop the crack is likely to lift off once the cooling system is pressurized.

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Fred Hoelzle

If you buy a NEW Behr radiatiator the fact is you won't be getting a similar defective part. The OEM radiator on my '91 had an UNREINFORCED upper hose neck (I assume yours on your '92 was similar) and I opted for the peace of mind and bought the new radiator with the reinforced hose neck.

You could engineer a repair on the one you have but if the original radiator already has 75,000-100,000 miles on it it could be considered a consumable item and you could simply replace the whole thing. I personally don't care for the risk of a quick catastrophic failure...

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1991 560 SEC AMG, 199k <---- 300 hp 10:1 ECE euro HV ...

1995 E 420, 170k "The Red Plum" (sold)

2015 BMW 535i xdrive awd Stage 1 DINAN, 6k, <----364 hp

1967 Mercury Cougar, 49k

2013 Jaguar XF, 20k <----340 hp Supercharged, All Wheel Drive (sold)

Look here:

Radiator Neck Fix/Preventive Maintenance

For now, I would suggest getting some QuickSteel epoxy from the automotive section of WalMart, or an auto parts store. If you do a good patch job, it will seal the leak for at least a year, but the crack will slowly continue to spread.

Use more epoxy, and cover more surface area, than you think you will need. That will help slow the spread of the crack.

In the end, water + heat will win the battle, but I have fought it successfully for 4 years with this easy, fast fix.

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2008 E350 4matic / Black/Anthracite

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Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black

1-inch copper bushing from Home Depot fits perfectly.

Superglue will not work. It cannot withstand the heat and water.

Standard JB Weld is not waterproof and will deteriorate. There is a waterproof JB Weld, but I don't know how heat resistant it is. Steel epoxy works best.

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2008 E350 4matic / Black/Anthracite

------------------------------------
Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black

You are correct to patch it.

If it leaks, you are not maintaining pressure, thus you are running hotter than necessary. And that small crack, because of its location, will eventually become a big crack.

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2008 E350 4matic / Black/Anthracite

------------------------------------
Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black

Many thanks for responses to my problem. I haven't had time to work on/find solution to leak since my last post. Never liked the idea of mating plastic to metal to confine a liquid that is subject to changes in temperature and pressure...bound to fail. The idea of reinforcement with metal at neck sounds like something a good engineer would have thought about in design phase. Eric, I see where you have a different auto, the 1" copper bushing may not fit the 500 SL neck. I have not removed upper hose to measure ID but, did measure OD (1.5") and doubt it will provide necessary fit. I can always try a larger bushing (copper or brass) cut it longitudinally and solder it. Regarding corrosion, the copper can be tinned with lead.

Finally received the following answer as to repair of radiator crack from Product Development Manager, Urethane Supply Company: "The radiator for your model Mercedes Benz is made from Nylon and really, the only way to repair it is to weld the crack. You will need an airless welder, some Nylon welding rod and a piece of stainless steel mesh. Just V groove out the crack then weld it back together, making sure the base material is blended with the rod (use a heat gun to preheat the area) then sink in some mesh over the repair to help tie it all together, followed by some more rod. It will probably not look pretty, but it will be strong and should not leak."

Question: Has anyone in forum tried this method of repair. I welcome any comments.

Now that I know the material is Nylon, I will use an adhesive specific for Nylon and a Nylon patch before trying the more difficult welding procedure. Since I will be draining radiator, I intend to flush out cooling system. Anyone have advice as to proper and tried method of flushing out cooling system.

It is less costly, and less time consuming, to replace the radiator. There are some on EBay right now for about $100. The welding process will almost surely be more expensive -- especially if it does not work the first time.

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2008 E350 4matic / Black/Anthracite

------------------------------------
Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black