300D Runs Hot - PeachParts Mercedes-Benz Forum

Uncle Billy Bob · #1 04-12-2013, 09:51 AM

1980 300d Non Turbo. Replaced radiator with all metal one (supposedly rebuilt), replaced temp sender, swapped guage, new thermostat (twice), new water pump. Chk temp w/ infrared guage is pretty close. I have the aux fan running constantly as well. cirtus flush etc...

The car runs about 90-95C in town but on hills it runs up and well over 100C. The temp keeps going up on hills so something is not keeping up. Also at 65mph maintains 90C but at 70-75 it goes up to 100C. Does anyone have any suggestions on how to bring down the temp? Is it possible to put a turbo radiator w/ overflow on this engine? Would it do anything? Non turbo 5 Cyl radiators are not available new anymore.

I tried everything I can think of. trans is decent shifts ok. with summer coming I want to fix he a/c. Then it run even hotter. any ideas?

Stretch · #2 04-12-2013, 09:55 AM

If you were to use the turbo radiator then you'd need the expansion tank too - the turbo radiator doesn't have a cap like the non turbo one (on the radiator).

marco5 · #3 04-12-2013, 09:57 AM

Nothing to be concerned about unless you are hitting temps of 115+. These engines are very old and can not be expected to run flawless. I would flush the coolant a few times. First drain your old coolant, then flush with distilled water and acidic products for flushing coolant.

Then flush with all water.

Then fill with OEM Coolant and distilled water 60/40, may also want to replace your water pump and flush your heater core. Confirm the subpump is running etc.

charmalu · #4 04-12-2013, 10:27 AM

Quote:

Originally Posted by marco5

Nothing to be concerned about unless you are hitting temps of 115+. These engines are very old and can not be expected to run flawless. I would flush the coolant a few times. First drain your old coolant, then flush with distilled water and acidic products for flushing coolant.

Then flush with all water.

Then fill with OEM Coolant and distilled water 60/40, may also want to replace your water pump and flush your heater core. Confirm the subpump is running etc.

Did you over read what he said here?

"Replaced radiator with all metal one (supposedly rebuilt), replaced temp sender, swapped guage, new thermostat (twice), new water pump. Chk temp w/ infrared guage is pretty close. I have the aux fan running constantly as well. cirtus flush...."

Did you raise the front of the vehicle and fill the upper Radiator hose? this is mentioned a lot here, to purge the air that gets trapped.

Could be your new Thermostat isn`t opening up enough. check it in a pan of boling water with a thermometer. place some salt in the water to keep down the bubbles.

Charlie

Uncle Billy Bob · #5 04-12-2013, 11:01 AM

I did citrus flush the system, the engine was unbelievably clean. I did not raise the front end up though, but I think I checked it on a hill later and ran it without the cap on for some time.

This week I drove it about 800 miles round trip. On this trip I hit 105C on a hill. The temp keeps going up as long as you're running it hard. I've seen it hit 115C on big mtns in VA when it's 95 degrees out. I don't worry about it too much now but if I get the a/c going is going to be a problem I think.

The turbo radiator has more cooling capacity? I can easily add one and the exp tank of course. I wonder if that would do anything?

BillGrissom · #6 04-12-2013, 11:40 AM

Long ago, I have seen radiator guys test for clogged tubes by flowing water thru from a garden hose. A rough check, but gives a good idea. When I have one off, I have flipped the radiator upside down, rigged a hose connection to the bottom from a garden hose (fittings at Home Depot), I fill, hold the upper outlet (now at bottom) to build up a little pressure (not too high since water supply can be >60 psi), then let go to release a surge of water that maybe breaks loose rust. At least this is a reverse flush. If not clogged, the water should flow out about as fast as your can fill it from a garden hose. Never done on a M-B radiator, but should work the same.

You might check that your mechanical fan has a good clutch. It looks like many U.S. fan/clutches would fit the water pump, judging from my Mopars.

The best radiators for cooling are aluminum and there are many after-market ones on ebay. I got a new all-alum one on ebay for my 65 Newport, which always liked to boil over. That is an endemic problem for muscle car owners. I think diesels have less heating issues, so should be an easier problem to solve.

Finally, have you checked the water pump? Not very easy to do. I have heard of people (non M-B) finding the impeller totally eroded away or the shaft broken just after the bearing so that the impeller wasn't turning. You might test the pump for flow by disconnecting an outlet hose and running the engine with straight water.

charmalu · #7 04-12-2013, 11:46 AM

The Turbo Radiator is larger from what I remember seeing these 300D NA in the yards. Even with greater cooling capacity, the Thermostat
What temp Thermostat are you using and brand?

Charlie

Shortsguy1 · #8 04-12-2013, 05:31 PM

Quote:

Originally Posted by charmalu

Could be your new Thermostat isn`t opening up enough. check it in a pan of boling water with a thermometer. place some salt in the water to keep down the bubbles.

Charlie

Charlie and others... How does the OP (and myself) know if the thermostat is "opening enough?" I just did the experiment you described for the first time in my life, so I have no reference for how much it should open. I was a little surprised how little my new behr 79C thermostat opened. I would guess there was probably at most a 3/8" opening all the way around when full opened. For some reason, I was expecting the opening to be huge so that it wouldn't restrict the flow at all. Does anyone know specifically what the "travel" is supposed to be on a good thermostat?

Uncle Billy Bob · #9 04-13-2013, 09:04 AM

I replaced the water pump last year and removed the brand new china thermostat and installed a Behr thermostat.

I have not replaced the fan clutch but it runs hotter when on the highway at higher speed. In town does ok and the fan is spinning when I start the car. I was also giving a thought to putting a constant running fan on it like my 240d has. Well that probably won't do anything....

The turbo radiator is the same width, it should fit but may be thicker not sure. I guess I can buy one and try it. I really don't want to use another used radiator in here but doing that garden hose test makes sense.

barry12345 · #10 04-13-2013, 10:32 AM

Well if I were this far along the pike I would do the test for exhaust gas componnents in the coolant. You need a more solid indication one way or another of where the problem is.

If the coolant is clean by test then check the injection pump timing. Do you have any ideal of your current fuel milage? Does the car have normal acceleration as a partially obstructed exhaust might heat things up somewhat as well. I hope you did not just get a bad rad.

Also read the oil cooler when the engine is running hot. Be careful though as technically it can be much hotter than boiling water.It should be hot as well then. These cars will run with a defective oil cooler thermostat. Base oil does not boil untill 400-600 degrees so do not use your hand for this test. A normal car should not need the assistance of the fan at highway speeds so you can discount the fan clutch basically. Or when you turn off a hot engine the fan should stop pretty fast as well is a fair test.

t walgamuth · #11 04-13-2013, 11:14 AM

I think a test of the stat is a good idea. did you check what temp is stamped on it? It actually sounds like it could just be a 90 degree stat to me.

big d · #12 04-13-2013, 10:28 PM

Maybe you can try to run without thermostat and see what is going on.This can give you some idea .

Uncle Billy Bob · #13 04-14-2013, 11:07 AM

The thermostat is a 80C behr new. Previously had a china 80C thermostat in it installed new by a mechanic. I didn't test either but no difference btwn the 2. The China one worked for sure as the prev thermostat was stuck.

I think the idea of the oil cooler is probable. It gets warm to the touch but not really hot. I didn't take a temp reading on it but is not getting as hot as the coolant radiator for sure. I can leave my hand on it is just warm.

Is there a way to test the oil thermostat? I assume it's in the oil filter resevoir? Replacing the oil cooler, lines and filter housing would not be a job to look forward to and very pricey. I would prefer to test it before replacing all the parts.

barry12345 · #14 04-14-2013, 12:44 PM

Quote:

Originally Posted by Uncle Billy Bob

The thermostat is a 80C behr new. Previously had a china 80C thermostat in it installed new by a mechanic. I didn't test either but no difference btwn the 2. The China one worked for sure as the prev thermostat was stuck.

I think the idea of the oil cooler is probable. It gets warm to the touch but not really hot. I didn't take a temp reading on it but is not getting as hot as the coolant radiator for sure. I can leave my hand on it is just warm.

Is there a way to test the oil thermostat? I assume it's in the oil filter resevoir? Replacing the oil cooler, lines and filter housing would not be a job to look forward to and very pricey. I would prefer to test it before replacing all the parts.

You want to have a good hard longish run on that car before deciding on the oil cooler thermostat. Summer temperatures as well.

It may only be me but I think I would still test the coolant for any presence of exhaust components. It is a cheap test and at least gets that possibility out of the way. A slight head gasket leakage could enable this problem. These cars are old and nothing lasts forever so many things become suspect.

Stevo · #15 04-14-2013, 09:23 PM

The Behr T stat should have an arrow to indicate which way goes up, you installed it according to that right? Theres a thread over on benzworld where the poster is having a smiler problem after installing a Behr T stat and not seeing the arrow, maybe it doesn't make a difference, but it might.

T-Stat Orientation Arrow -Important or Not?