Whats left??? - PeachParts Mercedes-Benz Forum

#1 10-30-2003, 03:56 PM

OK, I've posted before about having a "running warm" condition on the 84 Euro. Well, now it's back, and the only way to keep the temps down is to keep the car out of 5th. It doesn't matter if I'm on flat or hilly ground, the temp guage gradually creeps up over 100C in 5th.

It has a new water pump, new radiator, new T-Stat, new radiator cap, and total coolant system flush (lots o' crap came outta that). The hoses are in new condition, and aren't restricting flow. I'm not using any coolant, nor oil. I see no indications of coolant in the exhaust. The injectors passed testing, despite there always being a continual light trail of smoke, with a fuel odor. I want to get the A/C fixed, and be able to do road trips in this car, but cannot untill I get a lid on this annoyance. Any ideas? I'm stumped.

R Leo · #2 10-30-2003, 04:18 PM

You're getting too much fuel at WOT. Try turning the ALDA adjustment screw 1/4 - 1/2 turn CW.

JimSmith · #3 10-30-2003, 04:23 PM

Diesel Power,

Your problem is most likely a water or air flow problem as when you drive in 5th gear, the load on the engine is highest and the water flow rate is lowest. Any air flow restrictions and you may well be unable to remove the heat at the rate the engine is making it.

You might consider examining the air conditioning condensor which is in front of the radiator to see if it is clogged with twenty years of bugs being sacrificed to getting you from here to there, or other road junk, and corrosion. These units are usually painted and when they get real old sometimes the metal underneath is exposed by abrasion, leading to oxidation of the material. Eventually the paint can start to flake off and block the air passages.

Another common problem is a thermostat that is not set or built correctly. Even new ones come out of the box and do not work correctly. Try boiling it in a pot of water with a thermometer to see if it opens when it should. Remember, these thermostats have two functions, one is regulating flow to the radiator, and one is regulating the flow that bypasses the radiator and mixes with the cold water from the radiator before it goes into the head. In the overheating condition the thermostat should be blocking all bypass flow and sending all the water pump output to the radiator.

There is one thing to consider with the water pump. The 5 speed unit may have a different water pump than the 4 speeds and automatics. You may want to check to see, if the water pump has ever been replaced, if the water pumps for these cars are all the same part number. Given the 5 speed unit has an overdrive ratio, it may require a higher flow rate to handle the heat load. I am just guessing here though.

Good luck, and I hope this helps. Jim

JimSmith · #4 10-30-2003, 04:26 PM

RLeo,

I don't think the 240D "ALDA is the same as the "ALDA" on a turbo. On a 240D the thing in the place of the 300D TurboDiesel "ALDA" only compensates for altitude when you cross the Alps or Rockies or the like. Jim

engatwork · #5 10-30-2003, 06:11 PM

How high over 100 does it get? I remember the 240D (manual) I had would get to 100 when run at wot on the interstate. As long as the temp drops when you back down then it is probably cooling as well as it can. The answer may be a larger radiator if you could get one in there. As long as it stays out of the red you should be able to run it.

kerry · #6 10-30-2003, 06:14 PM

If it has a fan clutch, check to make sure that it is working.

engatwork · #7 10-30-2003, 06:17 PM

Fan clutch is out of the picture in 5th going down the highway at 60+ mph.

kerry · #8 10-30-2003, 06:23 PM

Not so. I just put a fan clutch on my 409d. I was running without a fan at all prior to that. At 60mph down the highway it runs cooler with the clutch than without a fan at all. Surprising I know but empirically verified. Similar situation with my Olds. It was running hot going down the highway at 60. Replaced the fan clutch and problem was solved.

Stevo · #9 10-30-2003, 06:50 PM

Diesel Power

Check your PMs

Steve

engatwork · #10 10-30-2003, 07:37 PM

Surprising I know but empirically verified. - I would not have thought that. The two 240D's I have been around did not have fan clutches. Not sure about the one in question.

#11 10-30-2003, 09:56 PM

My 240D does not have a fan clutch. They are solidly mounted to the pully, and they turn continuously (I wonder how much power could be found by changing this). I checked the condensor the following morning after getting to where I could think beyond being ticked off over the old problem all over again. It is acutally in surprisingly good condition, and I could see right through it all across the facing.

Egnatawork, It'll gradually creep up to about 105, where the guage starts to jump around erraticly between 105 and 115. I've never seen it hit the red line, but don't trust it's accuracy at that point. Unfortunately, this is the guage set out of the 80 240D, which had overheated before the guage indicated that it was hot when the harmonic balancer went south. The rheostat for the cluster lights went bad on the one for this car, and I haven't yet had the time to figure out how to transplant the rheostats without destroying the circuit board.

Once I get it off of the highway, and back into lower gears and speeds, the temps will normalize to around 90 - which is where this thermostat seems to want to keep the temp.

leathermang · #12 10-31-2003, 06:56 AM

You may not want to hear this... but you may be driving it out of its power curve... this car was made in " the land of no speed limit autobahn' .... and any car needs to be in a certain rpm area not to overheat. IT IS A EURO... not built to be sent to the US.. you may just not have the Asphalt out in front of you to utilize 5th gear.. without changing the rear axle ratio....
Your car might do just fine in 5th at 95... but how long will you still have a license here in Texas if you practice that often ?
I assume that because you checked the injectors that you know your fuel timing is right on the money... on gas engines the timing of the ignition will affect the temp quickly...
Because I consider this a problem of efficiency.... I wonder when the little holes in the precombustion chamber were checked for cleanlyness ? Holes clogged can narrow your acceptable power band.
On some engines I have seen in the past... the water pump had FEWER vanes on it when the car had air conditioning... I was really surprised because that is opposite to my logic.. but it was something like" to keep the water in the air stream longer" before it got back to the engine....

leathermang · #13 10-31-2003, 07:07 AM

OK,, another possibility.... and I am assuming that you did the flush Because it was having this overheating ....
Take out the freeze/core plugs and use a pressure washer with a 90 degree tip to stir up the stuff which has accumulated in the square corners of your coolant cavities... this stuff is harded up to where a simple flush will not move it...
AND you need to suck it out with something like a shop vac... because the size of the drain hole is just not big enough to get the flow necessary to get rid of this stuff...
In the old days... when an engine was rebuilt.... they were stripped of everything which would bolt off... and taken to a VAT and ' boiled' out.... this would get this stuff out before the next set of insides had a chance to start heating up the engine...
I have never heard of anyone starting to rebuild a MB , even when they were planning on putting new sleeves in... planning on vatting the engine block...

#14 10-31-2003, 11:29 AM

I did the flush to insure that all of that oily gunk was out of the car to prevent plugging the new radiator. The old one was partially clogged.

I had thought of the power band thing, which was what caused me to try driving in 4th. My only concern though is, that the temps will still rise in 5th even during conditions of very light to no throttle. On flat ground the car should be able to propel itself in top gear without undue stress, even an underpowered one.

leathermang · #15 10-31-2003, 12:26 PM

Light throttle is even worse...
If you are running in a differential gear/ transmission gear combo which puts your engine below its ability to produce the power EASILY for pushing your car it is going to start overheating... You are lugging the engine...