radiator leak - PeachParts Mercedes-Benz Forum

chisholm · #1 02-05-2003, 08:25 PM

After seeing several posts on the 'normal' operating temperature for a 300D, I installed a new thermostat. Now the gauge reads the expected 80-85C with all the benefits of a warm engine and radiator. The only downside to this repair is a small coolant leak. I first thought it was coming from the radiator drain plug, but I am still getting a few drops/min. after replacing it. It did not leak before I replaced the thermostat so what have I done? Would air in the cooling system result in a higher pressure in the system? If so, how do I get the air out?

lrg · #2 02-05-2003, 08:58 PM

A hotter cooling system will tend to have slightly more pressure so you may be seeing a leak that you've always had but are just now seeing. Are you sure the leak is around the radiator plug? If you removed the plug to drain the system before you replaced the thermostat it's possible you put a small crack in the radiator when taking out the plug. If the radiator is OK and the leak is definitely around the plug, try removing the plug and wrapping a small amount of plumber's teflon tape around the threads before you screw it back in. You can buy teflon tape at any hardware store. Don't put more than 1-2 wraps around the plug and then only on the threads. Air in your system, unless there is a whole lot of it, shouldn't add any pressure. It sounds like you just need to check for a possible crack in the radiator at the plug or simply reseal the plug.

rwthomas1 · #3 02-05-2003, 10:46 PM

My Benz had a very small puddle of coolant under her today after a 3 1/2hr run on the highway. After checking everything it appears it was just a slightly loose clamp on the upper radiator hose. I put on a new rad cap to be safe and can't see anymore coolant leaking yet. Check your clamps! RT

#4 02-06-2003, 07:33 AM

rw is on it. You need to start by tightening all your hose clamps and start looking dilligently until you locate the exact location of the leak.

The bottom radiator hose is near the plug, so you certainly need to check it.

Good luck,

chisholm · #5 02-08-2003, 03:36 PM

Thanks for the suggestions. I have tightened the hose clamps at the bottom of the radiator. It was not obvious which one (if any) was leaking. It looks like the coolant collects along the lip of the fan shroud. That is probably why it looked like it was dripping from the drain plug. The good news is that the clamps could be tightened. After a test drive I saw no signs of coolant so I hope that has cured the problem. It looks like the radiator end caps (plastic?) are attached to the metal section by a series of crimped metal tabs. How likely is it that the joint between the two units will leak?

samiam4 · #6 02-08-2003, 11:07 PM

If you eliminate all the other leaking locations- the crimp joints do leak eventually( sometimes).

If you have everything working- the hailMary of leak repair seems to be 2 GM "coolant tabs". Seen it as the latest and greatest trend in semi-shady wrenches.

Michael

slowmoe · #7 02-09-2003, 08:42 PM

If after tightening everything as recommended, you can not locate the leak, I would recomend removing the radiator and taking it to your local radiator repair shop. They will be able to pressure test it there and determine if it is repairable. If not, put in a new one, replace your hoses for good measure and be done with the cooling system for the next few decades

samiam4 · #8 02-09-2003, 11:36 PM

If you need one...

I heard a rummor last week that MB axed radiator prices. Now they may be cheaper than aftermarket.

Coolant tabs do work and it's about $255 cheaper than a new radiator=)

Michael