1972 280 SE 4.5 Overheating - PeachParts Mercedes-Benz Forum

noel.brownell · #1 01-09-2009, 10:15 PM

I recently noticed that my radiator was slowly leaking radiator fluid when it sat to cool and that it was running a little warm at stop lights. The temp goes up from around 175 F to 185 F when idling. Today it got up to 210 F or so and was spraying steam. The fan in front of the radiator is not working and I think I have a small hole in the radiator near the top at the water insertion point. I need to fix this problem asap as this is my daily driver. Any suggestions? (There is a 72 mercedes with a 6 cylinder at the wrecking yard, will this radiator work or do I need a radiator from a V-8?) Are there any restrictions on the years I can pull a radiator from? Lastly can I put some sort of sealant in the radiator until I get one from the wrecking yard to put in the radiator and seal the leak? It only leaks under sprays when the heat gets too high and this is the first time it went above 185 F. Thanks ahead of time.

gmatthewb · #2 01-09-2009, 10:58 PM

Hi. I had this same issue last year. Mine would begin to run 'warm' when it was in stop & go traffic or at red lights. I wouldn't recommend running the car very much at all. Cab fare is much cheaper than replacing head gaskets.

The radiator cap has two 'stops'. After you set the cap in place, only turn it ONE 'stop' to the right instead of two. This allows excess pressure to vent out of the cooling system instead of building up and increasing the presure, then pushing the coolant through the pin-hole.

I had my radiator re-cored. The build-up inside the radiator was too much to repair. I had them re-core the original two-tube radiator with a three-tube core. I was told that it allowed for more water flow and cooling surface area. Not sure about this, but I can tell you it runs very cool, even in the summer with the AC cranked.

I would also recommend replacing the thermostat AND the radiator mount (kit is available online). I wasn't going to do the kit b/c of price, but I'm glad I did. It took care of one of the rumbling sounds that I was hearing.

Good luck.
G. Matthew B.
gmatthewb@yahoo.com

noel.brownell · #3 01-10-2009, 09:17 AM

Does anyone have any suggestions as to which radiators will fit in my 72 4.5. Unfortunatly this is my daily driver and I am looking to find another radiator, have it cleaned and pressure tested and replace my existing one. The fan on the front of my radiator is not working and I was wondering if anyone has run into this problem?

Tomguy · #4 01-10-2009, 10:05 AM

The aux fan not working combined with a weakened fan clutch (they wear with age or lock up, yours sounds like it doesn't grab anymore) results in overheating at idle, and when you begin moving over 40 you see the temp drop rapidly. That's a telltale sign of fan failure. Even a new radiator won't help that situation. You really should replace the front aux fan with a good used one, and the fan clutch (with a used one if you're on a budget). The radiator must be from a 3.5 or a 4.5 108 or 109. The inlet or outlet is on the wrong side from the 6-cyls. I forget which. It's also substantially smaller, a leaky 4.5 radiator with corrosion probably still cools better. I do agree with the cap suggestion, mine leaked from the seam too. Make sure you fill the radiator all the way up to the indentation inside (it looks like a wedge-shaped notch from the outside, on the engine side of the radiator). Not doing this results in rapid overheating because your coolant goes through only about 1/4 of the radiator.

If you're on a budget you can fix a seam leak yourself if you have moderate technical skills. I used silver solder and a ton of flux paste and did mine, and it held for well over a year until I decided I wanted to fix a tiny tiny leak on the end and wound up messing it up beyond the point I could fix it with my then-limited resources (no garage to shade from wind and no dremel to clean out the old paint and rust).

noel.brownell · #5 01-10-2009, 11:09 AM

Tom Guy,

You always give good advice! Thanks. What is involved in replacing a fan clutch?

Tomguy · #6 01-10-2009, 11:39 AM

You need a known good clutch from a 4.5 used or a new one. I don't think they fit from 3.5's but I could be mistaken.

You'll want to remove 3 of the 4 bolts holding the fan assembly to the water pump, just loosen the 4th (don't remove it or reinstalling the pulley to the water pump may mean you need to loosen the PS pump and re-tension). I can slide the assembly out without removing the shroud, I just remove the top radiator hose. My shroud is cracked so I have room, you may need to remove it (4 bolts). There are 4 bolts connecting the fan to the clutch.

You'll know the clutch is bad if your engine is warm (175 or higher) and it's really easy to move the fan. It should have some fair resistance to it.

JMela · #7 01-10-2009, 04:51 PM

EZ fan clutch test - if you can stop your fan from spinning with a rolled-up newspaper, it's shot.

noel.brownell · #8 01-11-2009, 09:30 AM

Thanks for all of the great advice. Unfortunatly I pulled the clutch before doing the newspaper test but I will make sure to test it when it is back together. I am doing the radiator repairs this morning and I found a working aux fan at the bone yard.

kickstart111 · #9 01-11-2009, 11:47 AM

PLEASE NEVER put anything in a moving fan or around any moving engine parts! there are far better and safer ways to check things.I have seen to many missing and damaged body parts because of this