'91 - 124: 300E Upper radiator hose clap tightening
 

I am replacing the radiator and wondered how tight the upper radiator hose clap should be.

My question is regarding this common failure. Is it related to over-tightening the clamp or is this just material failure?

Haasman

Did the old rad fail because the plastic Hose outlet cracked?

If so, this could be another example of the famous "cooling-system-alkali-embrittlement"

Some say that the type of plastic used in our cooling systems get brittle if exposed to fluid which has any other PH than 7.0 (neutral).

There's lots of circumstantial evidence to support this.

I guess the advice now that you've changed the rad is to check the PH of the fluid and add anti-freeze untill it sits at 7.0.

As far as how tight to do up the jubilee clip..............do it no tighter than required to stop a leak. Any more will stress ths plastic.

Paul

Forgive me, but how does one check the coolant PH?

PH meter (from Gardening shop).

You could use litmus paper and gauge it from the colour change (assuming fluid is clean and not too colourful)

The normal recommendation is to use genuine MB antifreeze, but there are plenty of other good ones around.

I read about the following technique at this site some time ago. I believe that Benzmac mentioned this approach.

Before you change coolant/hoses/etc. Go rent a cooling system pressure tester. These are easy to use and are great for finding coolant leaks anyway.

After you get your hoses on, tighten up the clamps a bit 'til they're fairly snug, but not too snug. Connect the tester to your overflow tank and pump up to about 15-17 lbs. The system is likely rated at 20 lbs, but I like to back off a bit from this so I don't blow the seal on the water pump.

Watch for leaks at the ends of the hoses and tigten gradually until the leakage stops. I like to see the system as a whole hold 15-17 lbs of pressure for at least 20 mins.

Haasmaan,
You mentioned that you're changing the radiator. If that's the case the replacement one should already come with the metal insert inside the top hose.
The reason the original breake is because they didnt have the metal inserts and the plastic always breaks off at one point or the other.

Thanks everyone. Great tips and advice. This is a great group!

I will look for the metal insert. Also would the infamous 50/50 ratio ensure a correct PH, or close to?

Haasman

Don't be surprised if you order a new Behr radiator and it does not come with a metal sleeze. Many of the newer models being shipped no longer contain this enhancement.

When I bought mine from the dealer, it had the metal insert. Not sure about the aftermarket ones. I guess it's best to confirm before buying it.