100 C, upper hose hotter than hell. overflow tank cold, HELP!!! - PeachParts Mercedes-Benz Forum

rickjordan · #1 04-08-2006, 08:20 AM

My '83TD lately has been running increasingly hot. Last night she hit 100-105 C. I checked, in the dark, the expansion tank and the fluid level was fine, but oddly the cap was cold, stone cold. The upper radiator hose was real hot. I was actually able to take the expansion tank cap off with out any hissing, zip, nothing it was like there was no pressure in the system.
ANY ideas would greatly sppreciated.

Brian Carlton · #2 04-08-2006, 09:34 AM

After it gets hot, reach underneath and feel the two lower hoses. The large hose returns coolant to the water pump and the small hose goes to the expansion tank.

What's the temperature of the two hoses?

Could be low flow through the radiator if the large lower hose is also reasonably cool. But, I really don't have enough info for an intelligent guess.

MBeige · #3 04-08-2006, 03:45 PM

Sounds like a clogged radiator. Do you have heat?

Diesel Giant · #4 04-08-2006, 05:53 PM

Oh no the dreaded 617 overheating is starting again. When was the last time you changed your t-stat? Radiator flush? Make sure your fan clutch is operational.

rickjordan · #5 04-08-2006, 06:09 PM

Ok, the lower hoses, as well as the lower portion of the radiator are cold, not luke warm, cold. The T-stat was shanged out 3 years ago. with a Behr. I used 50/50 MB coolant and water. That was the last time the cooling system was drained. The coolant that's in the expansion tank is clean, no crud or anything.
Is there anything I cam run through the system to free things up? I ran into this once before with a Datsun 280ZX and ended up replacing the radiator. I guess I could remove the upper house and try and see inside.
Any other suggestions?

Brian Carlton · #6 04-08-2006, 06:12 PM

Quote:

Originally Posted by rickjordan

Ok, the lower hoses, as well as the lower portion of the radiator are cold, not luke warm, cold. The T-stat was shanged out 3 years ago. with a Behr. I used 50/50 MB coolant and water. That was the last time the cooling system was drained. The coolant that's in the expansion tank is clean, no crud or anything.
Is there anything I cam run through the system to free things up? I ran into this once before with a Datsun 280ZX and ended up replacing the radiator. I guess I could remove the upper house and try and see inside.
Any other suggestions?

Classic plugged radiator.

You can try a citric acid flush, but, no odds on it working with such blockage that allows almost no flow.

rickjordan · #7 04-08-2006, 06:27 PM

That's what I was afraid of. I am glad the radiator on my 911 is guaranteed (sp) for life

will_sanderson · #8 04-08-2006, 06:58 PM

I've been having similar issues and found a good inexpensive radiator at www.radiatorexpress.com $160 1yr. warranty $190 3yr. Good luck

dieseldiehard · #9 04-08-2006, 08:44 PM

Quote:

Originally Posted by rickjordan

Ok, the lower hoses, as well as the lower portion of the radiator are cold, not luke warm, cold. The T-stat was shanged out 3 years ago. with a Behr. I used 50/50 MB coolant and water. That was the last time the cooling system was drained. The coolant that's in the expansion tank is clean, no crud or anything.
Is there anything I cam run through the system to free things up? I ran into this once before with a Datsun 280ZX and ended up replacing the radiator. I guess I could remove the upper house and try and see inside.
Any other suggestions?

The lower hose is always cooler than the upper hose, and there is no path for flow up into the coolant reservoir so I would not even be concerned with the tem of the cap since its not at the hot area anyhow. If your seeing over 90 in a 617 in the winter then something is definitely wrong, most likely a lot of scale in the radiator.

Diesel Giant · #10 04-08-2006, 10:48 PM

3 years on the coolant flush??

You definately need to do a citrus flush and maybe a new radiator.

P.E.Haiges · #11 04-08-2006, 11:22 PM

Rick,

It might be a bad water pump, like the impeller slipping on the shaft.

A radiator doesn't plug up that fast, takes years.

P E H

rickjordan · #12 04-09-2006, 01:53 PM

I'll check and see if the pump is leaking (bad bearing). When I said the lower hoses were cold, I mean cold. Not relative to the temp of the upper hose, I mean cold, so was the lower tank. I would certainly expect the lower portion of the rad. and hose to be luke warm if the upper portion is hot.

73MB280SEL · #13 04-09-2006, 04:06 PM

I'm with PEH. Just because coolant is not flowing through the radiator doesn't mean it CAN'T flow through the radiator. If the t-stat isn't opening, the lower hose will be ice cold.

Two ways that the t-stat doesn't open: (1) it's stuck closed and (2) the coolant pump isn't moving enough fluid to heat the t-stat to it's opening temp.

On my car (W201 190D 2.2), I replaced the coolant pump with a cheapie-rebuilt and made the problem worse. Then I got a quality rebuild from the dealer and it works properly.

Sholin

rickjordan · #14 04-09-2006, 07:19 PM

The radiator is not original, and I don't know when it was replaced. I have had the car since Nov. 2001.
I haven't messed with the car. It was real nice out today and couldn't resist driving the 911. I suspect that the water will be cold and then hot, just as it was on my old 280ZX. I have noticed that the temp rises quickly, which tells me that the T-stat may be stuck closed, but then again, it's only 3 years old. I would imagine that a Behr t-stat would last longer.

73MB280SEL · #15 04-10-2006, 12:45 PM

Here's a test you can perform to see if the radiator/coolant pump has enough capacity to cool the engine. Some may not agree with this test but it worked for me:

(1) order a new tstat.
(2) remove the old tstat and modify it by taking out the valve part leaving only the outer ring. This is a destructive process.
(3) install just the ring and gasket. This will effectively "open" the cooling circuit although it does not close the bypass path.
(4) run the engine. If the temp is low and the lower hose is warm, you are getting circulation through the radiator. If the temp is still high you may indeed have a plugged radiator.

You have to be careful with this test because it does not close the internal engine circulation path so it does not run all the coolant through the radiator. Think of it as "half cooling" mode. Even if you see your temps OK, you can still have insufficient circulation through the engine block to heat the existing t-stat, but it at least proves that the reason the engine is running hot is that the t-stat is not opening.

Sholin