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One of the BW Old Guard/R129, W204 Moderator
1997 SL500- 40th Anniversary
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7,160 Posts
Discussion Starter #1
Well, recently my 1988 560SL suffered from the typical "broken waterneck" so often discussed in forums in the past. Enough of the neck was still attached to the tank to allow the hose to stay on, so I bided my time in replacement, ordering an all-metal zeigler radiator in Jan. My goal was to replace the unit in late March or so, and the hoses (relatively new already), thermostat (age and temp unknown), and maybe the water pump.

Well, weather turned warm early here in the south, and I got anxious. I did not have the other parts in hand, and could not get them locally, so I decided to change the radiator out NOW and the rest at a later date.

Here is the rub... (The radiator fit OK, and looks great. All fittings, etc were where they were supposed to be, and the whole job was relatively painless, in spite of the unit not fitting the mounting without a little persuasion, and the rubber bushings for the bottom mounts had to be trimmed a bit to fit in the mounting rings on the bottom of the radiator). Today, ambient temp was 65F. My car, on a road trip of 75 miles at 70mph, ran a water temp of 85-90C, and climbed to almost 100C upon climbing a 3% or so grade for several miles. I had the AC on to cool the interior as the sun coming in was heating up my better half above her comfort level. I guess I expected the water temp to be closer to 80C since the ambient temp was cool. Last summer, even on the hottest day, I never saw the water temp at or above 100C, usually staying in the 80-90C range (which I always marvelled at). Oil pressure is 2.2 or so at idle when warm, 3 pegged at cruising rpm.

I am intrested in this groups opinion... Should I have replaced the radiator with a BEHR (with plastic tanks)? Is this water temp atypical?
 

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1978 280slc
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3,200 Posts
I don't know much about the mercedes radiator, but an all metal(not Aluminum) radiator is better than something with a plastic because you can do a flush on it. I'm not sure about the 560 but my 280 runs a little warm, above 80*C on a warm day, especially if I drive above 80mph. Take it easy if the weather is warm.
 

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Depends on the day!
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13,337 Posts
Your temp is rather high IMHO.. All my 560's, and my SL in particular run's Right at 80, 82 if I'm driving triple digit for extended periods. Maybe 83 on a Hot day w/ the AC on full, stop and go traffic.

Personally, I would have gone w/ the Behr..I run them in all my car's and am most pleased w/ their performance/reliability. I think it would have been wise to flush the radiator and heater core prior to your change, but now would be better late them never. MB makes their own citric acid flush which I have had good results with.
Also, check your fan clutch, it should offer a fair bit of resistance when you go to move the blades, if it spins very easily it's time to replace it.

Replacing the water pump and t-stat is a bit of a pain on these cars but it would be a good idea. Don't bother w/ the Laso pumps, they use graf housings and some internals sourced from I don't know where.. On car's I plan on keeping forever I replace them w/ genuine pumps, if $$ is a bit of a concern, then graf's are fine.

Also, did you use MB coolant??? Do NOT use ethylene glycol!!

I've also had good results using Redline's WaterWetter on car's that would run a bit warm.

Hope that helps, let me know if you have any other questions!

Jonathan
 

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560SL,380SL
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4,012 Posts
Replacing the water pump and t-stat is a bit of a pain on these cars but it would be a good idea. Don't bother w/ the Laso pumps, they use graf housings and some internals sourced from I don't know where.. On car's I plan on keeping forever I replace them w/ genuine pumps, if $$ is a bit of a concern, then graf's are fine.

Why do you think other pump mfr's are bad? I picked up a water pump from an Italian mfr and plan to install it preventatively on a 90K car.

How can you screw up a water pump? If you don't overtighten the belt or cavitate it, seems like 100k+ is not unreasonable...
 

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One of the BW Old Guard/R129, W204 Moderator
1997 SL500- 40th Anniversary
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7,160 Posts
Discussion Starter #6
jhodg...
Thanks for the reply (and the others as well...) I have been using the car the last few days on "fun runs" and have not seen the temp above 95 (mostly stop and go traffic at 80ish ambient). I discovered my gauge is skitzy (short or poor connection) and can read high. If I "wiggle" the dash a bit, I can make the needle jump way high! At the same time, my gas gauge jumps to high (full) and the oil press falls... I gues I need to measure my engine temp with my infrared temp gun to know exactly what it is.

"...Your temp is rather high IMHO.. All my 560's, and my SL in particular run's Right at 80, 82 if I'm driving triple digit for extended periods. Maybe 83 on a Hot day w/ the AC on full, stop and go traffic..."
My research indicates the tstat starts to open at 80, and is not fully open until 94... Seems to agree exactly with my engine temp. at this time, I do not know if I actually have a heating problem or not.

"...wise to flush the radiator and heater core prior to your change..."
Install was a brand new radiator, and drained coolant was suprisingly clean, so I did not flush.

"...check your fan clutch..."
As my condition described was on the highway at speed, does the clutch matter? It seems to have resistance to being moved by hand, and the fan sounds change when engine is accelerated above 3000rpm. I guess it is ok.

"...Also, did you use MB coolant??? ..."
No, I did not use MB coolant, but the red stuff made especially for aluminum engines (by peak, I believe). Do you think this is a problem? What is the MB coolant made of if not some variant of ethylene or polyethylene glycol?
 

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83 Astral Silver 280 SL
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daryn - 3/16/2005 9:15 PM

I don't know much about the mercedes radiator, but an all metal(not Aluminum) radiator is better than something with a plastic because you can do a flush on it. I'm not sure about the 560 but my 280 runs a little warm, above 80*C on a warm day, especially if I drive above 80mph. Take it easy if the weather is warm.
So does mine. If my experience with other high revving cars is any guide, its due to silt build up in the radiator. Replacing the radiator is the cure, since the real problem is an aged radiator that is flaking internally.

Kirk
83 280 SL 101k
Astral Silver over Navy
4 spd Auto
 

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What's wrong with ethylene glycol?

and what brand of water pump can I use if price is no object, since I understand there are no new mercedes pumps?

and what was the oem pump on a 88 560sl?
 

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1979 280SL, 1984 280SL
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5,641 Posts
Ears!

Your radiator is not the problem, I'm sure. Make sure all the air is out of the system, a pain in the neck on these cars. Eliminate the apparent ground problem your gage cluster has, and change the t-stat. I did this last year on my 560. I used an all-brass radiator (Behr are the only radiators I've ever had problems with) and my water temp is a rock solid 80c.
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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Three days short of the 5 year anniversary for the original post. We are sure quick with the answers.
(Iknow chief, I know)
 
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