107 radiator
 

Hop ethis cross-post is not breaking any rules... Not too much action in the 107 forum these days.

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 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)?

You probably introduced an air bubble into the engine...try running the heater on full blast and raise the front of the car up to urge the air out of the engine and into the hoses. I have had similar experiences with other cars.

Thermostat
 

I would remove the thermostat first and remove the spring etc. so that their is nothing to impede the coolant flow....You were going to replace it anyway...then I would test drive and check the temperature....If the temp. stays way down then you know you might just need a lower temp. thermostat and if you are lucky it will be about 80-85 and you have solved your problem...It will just take a few minutes longer to warm up....Jim

Thanks for the reply!

Intresting thought... I may just have to check that out.. Last weekend, when I completed the change-out, I thought I addressed the air pocket possibility adequately. I refilled the system, and ran the car briefly to raise the temp up enough to turn on the heater pump. After being satisfied I had adequately replenished the water, I drove the car for a bit, with the heater on full blast (it was a bit cooler last weekend). a couple of days later, I topped off the reservoir as it had dropped a bit as the car had completely cooled down (level was about 3/4 inch below indicator). On my shake-down run, I did not drive very far, or get out of the city, so today was really my first chance to check everything out. I guess an air pocket could still be hanging around; however, as I returned from my trip this evening, I was running the heater on 20C or so in auto mode to keep the cabin a bit warmer (ambient temp was 47F). Car behaved as earlier in the day...

Jim,
Thanks for the input. I am under the misguided notion that it is a NO-NO to run a 560 without a thermostat. The stat in a 560 is a two-stage design with built-in bypass.

I am now researching my literature for the correct temp stat so I can order and replace...

Simply make sure there are no obstrutions to the air flow thru the radiator, check the thermostat operation by dropping in hot water heated just past the operation temp of the thermostat or change it out, make sure the fluid level is topped off and that should be it.

It's also entirely possible that a piece of crud from the cooling system has partially obstructed the thermostat or some other point in the system when you drained it you might have loosened it up...its probably not a bad idea to take it out to inspect and replace it to eliminate it as the culprit as it is not a very expensive part to replace and can cause lots of heartache and damage if it fails.

Hello.........If you refill your cooling system through the upper radiator hose and then top off at the reservoir, you will fill any air pocket. Radiator could be defective too!

Thanks for the replies... Looks like I have more work to do. I suspect all is well, and I am just sensitive to the temp wondering about the quality of the zeigler all-metal (brass) radiator.