consistent hot running problem - PeachParts Mercedes-Benz Forum

JB3 · #1 11-21-2010, 06:22 PM

trying to identify what could be the core problem in my constant above 100C running engine.

here is the history-
-When I bought the car, it was running cold, 50C.
-Installed new thermostat, no change.
-verified that the gauge end of the temp sensor setup was good by grounding the lead wire to the block, which pegged it, and (I assume) indicated that the ground in the dash was good.
-replaced the temp sender with a spare used one, and it instantly started reading at around 100C when up to temp.
-Ordered a new sender, and replaced it, and the new one read 45C!
-took the KNOWN good sender out of my 240 and installed it, and it reads 105-115C on average!
-Verified this final temp with a temp gun, the engine appears to be operating at around 230-240 degrees when up to temp.

So far, ive flushed the cooling system a few times, replaced the radiator and water pump, pulled out and inspected the thermostat housing, and water pump housing for blockages, and each time, it runs a hair hotter on the gauge, and this is after its fully purged all air out of the system.

The engine runs well, starts well, and does not have a head gasket issue (yet), but it runs extremely hot, and so far, Im still not sure why. Could I have a massive blockage in the block itself somewhere? Any suggestions would be much appreciated.

toddyvol · #2 11-21-2010, 06:34 PM

Radiator cap new or old?

layback40 · #3 11-21-2010, 07:24 PM

Is this on a very hot day with the aircon on, trying to do 100mph up a hill?
Is your fan clutch working?
If you start it & let it just run, does it get that hot. What sort of running gets it to 105 ?
Exhaust blockage?
Very bad IP timing ?
Does the top radiator hose get very hot?
Where on the motor was your 105 seen?
You could have a bad thermostat.
So far you have replaced the easy things.

JB3 · #4 11-21-2010, 08:19 PM

Quote:

Originally Posted by layback40

Is this on a very hot day with the aircon on, trying to do 100mph up a hill?
Is your fan clutch working?
If you start it & let it just run, does it get that hot. What sort of running gets it to 105 ?
Exhaust blockage?
Very bad IP timing ?
Does the top radiator hose get very hot?
Where on the motor was your 105 seen?
You could have a bad thermostat.
So far you have replaced the easy things.

this is in local ambient temps, 30s-40s F. Normal running of driving around town. it does it at almost any outside temp, earlier it dipped down to ambient 25-28F and the car was still running hot, it never overheats, just runs high, this is what makes me think its maybe gauge related apart from the temp gun. (ill shoot it again later on)

Fan clutch is working, comparable in resistance to 2 other good 617 fan clutches

Gets that hot idling up. If you let it sit at idle, it will be a little less than the pic, but remains around 100C, again, at winter temperatures with even the heater blowing high. It reads that high just puttering around.

Exhaust is clear, engine returns excellent power, intake is also clear with new air filter

have not checked the IP timing, but valves have been recently adjusted (3500 miles ago) IP can't be that bad off with the vehicle performance doing so well.

Top Radiator hose seems to get up to temp normally.

Temps of 230-240 were shot off the block this last week, approx where the stock temp sensor is. This was using a borrowed temp gun from a shop I used to work for. Can someone else shoot their engine in the same place or say what they got there before? thats not that much hotter than normal coolant temps at 190-210, and maybe its common for that area. That would at least point me towards the gauge

yeah, checking the new thermostat for correct operation is my next move. Then I will move back to the gauge, maybe put another gauge on there to verify if this one is reading abnormally high.

Removed the radiator and swapped it when I discovered that the no name rad in the car does not exactly match a good nissens 300D rad I have as a spare as far as volume. Its a good 1/2 inch thinner with also less horizontal vanes, and on the off chance that there is an issue with what looks to be an accident repair radiator that was installed, I decided to put in the OEM nissens radiator. I figure they put in a non turbo 300D radiator.

Cap is also still original, will probably replace that as well just so I know everything is new or checked. It seems to be in good working order though.

I also pressure tested the cooling system, and it holds pressure normally. Apart from it reading so incredibly high, there are no other indications of any problems so far.

barry123400 · #5 11-22-2010, 03:22 PM

If you never boil over or lose coolant I would want to see the engine operating at that temperature if really there. Much less wear and better fuel milage result. Plus better heater output I suppose.

Also getting your hands on another thermal scanner is indicated just in case the one you used is not calibrated properly.

This is the older cast iron head and block. I really feel that if the operating temperature is really elevated a little it is better than cooler or what is thought normal.

You asking someone else to read their fully warmed up temperature on their engine is the place to go right now as you mentioned.. You really want the comparison numbers to decide on any course of action

. My gut feeling is even if yours really turns out to be higher I would want it. Soon enough we will probably prove we can get another one to three miles per gallon simply by increasing the operating temperature of these engines.

Another reason your car can cope if really a higher than average temperature is present. When the cooling system is asked to dump btus your differential temperature is higher in the fluid to air spectrum so it is more efficient.

To kind of sum this up. Your situation may be preferable to what is thought normal. You may be in an operational temperature area that has only positive benifits.

I would drive this car and keep an eye on it for any indications of a failing head gasket if the readings you get prove accurate and above typical. There are no positive indicators at all that the head gasket is bad now. It is just something to be aware of. A failing headgasket can raise temperatures.

toddyvol · #6 11-22-2010, 04:31 PM

Quote:

Originally Posted by dropnosky

this is in local ambient temps, 30s-40s F. Normal running of driving around town. it does it at almost any outside temp, earlier it dipped down to ambient 25-28F and the car was still running hot, it never overheats, just runs high, this is what makes me think its maybe gauge related apart from the temp gun. (ill shoot it again later on)

Fan clutch is working, comparable in resistance to 2 other good 617 fan clutches

Gets that hot idling up. If you let it sit at idle, it will be a little less than the pic, but remains around 100C, again, at winter temperatures with even the heater blowing high. It reads that high just puttering around.

Exhaust is clear, engine returns excellent power, intake is also clear with new air filter

have not checked the IP timing, but valves have been recently adjusted (3500 miles ago) IP can't be that bad off with the vehicle performance doing so well.

Top Radiator hose seems to get up to temp normally.

Temps of 230-240 were shot off the block this last week, approx where the stock temp sensor is. This was using a borrowed temp gun from a shop I used to work for. Can someone else shoot their engine in the same place or say what they got there before? thats not that much hotter than normal coolant temps at 190-210, and maybe its common for that area. That would at least point me towards the gauge

yeah, checking the new thermostat for correct operation is my next move. Then I will move back to the gauge, maybe put another gauge on there to verify if this one is reading abnormally high.

Removed the radiator and swapped it when I discovered that the no name rad in the car does not exactly match a good nissens 300D rad I have as a spare as far as volume. Its a good 1/2 inch thinner with also less horizontal vanes, and on the off chance that there is an issue with what looks to be an accident repair radiator that was installed, I decided to put in the OEM nissens radiator. I figure they put in a non turbo 300D radiator.

Cap is also still original, will probably replace that as well just so I know everything is new or checked. It seems to be in good working order though.

I also pressure tested the cooling system, and it holds pressure normally. Apart from it reading so incredibly high, there are no other indications of any problems so far.

My temps started rising to 100c a week or so ago. I have a brand new Nissens radiator, coolant changed, new Behr Thermostat, and new hoses installed. Only thing I did not change was the radiator cap when I did the radiator change. Well my cap must have been bad. I bought a new cap and all is now back to normal. I was sitting in traffic and it did rise to 95c but it quickly returned to normal.

Just my experience. I bought a cheapo cap at Advance Auto until I can get a good one ordered.

tangofox007 · #7 11-22-2010, 04:43 PM

Quote:

Originally Posted by dropnosky

I decided to put in the OEM nissens radiator.

Are you sure that "Nissens" and "OEM" belong in the same sentence when talking about a Mercedes ?

funola · #8 11-22-2010, 05:24 PM

Did the thicker Nissen radiator make it run cooler? My Behr is 1.25" thick. How thick are the 2 that you have? I agree with Barry that it is better to run at a higher (reasonable) temp. I have a 92C thermostat that I will be putting in soon. If you're gonna be around at the end of the week we can shoot your head with my gun. I also have a DVM with a thermocouple input we can take temp readings at various parts of the engine.

layback40 · #9 11-22-2010, 05:48 PM

If the temp is stable at that temp, it makes me think its thermostat related as the thermostat controls the temp under normal conditions.
While its good to run a diesel on the high side temp wise, you run a higher risk of overheat when you load the motor. It has cut a long way into your safety factor. You dont want temps that fluctuate while you drive. A rock steady temp under all conditions is ideal & suggests that your cooling system is in good shape and has plenty of spare capacity.
Does this temp remain the same even when the system is loaded up ( air con, high speed up a hill)?
With another thermostat it should control at a different temp.

JB3 · #10 11-23-2010, 07:14 AM

Quote:

Originally Posted by toddyvol

My temps started rising to 100c a week or so ago. I have a brand new Nissens radiator, coolant changed, new Behr Thermostat, and new hoses installed. Only thing I did not change was the radiator cap when I did the radiator change. Well my cap must have been bad. I bought a new cap and all is now back to normal. I was sitting in traffic and it did rise to 95c but it quickly returned to normal.

Just my experience. I bought a cheapo cap at Advance Auto until I can get a good one ordered.

Ive been leaving the car parked using a work van during the week, but before I left yesterday morning, I swapped out the cap with a new one from NAPA. I also bought another thermostat, but did not get the time to install.

JB3 · #11 11-23-2010, 07:16 AM

Quote:

Originally Posted by tangofox007

Are you sure that "Nissens" and "OEM" belong in the same sentence when talking about a Mercedes ?

not at all.

None were produced with a nissens radiator? only behr? Lets change that remark to I have a good nissens radiator that is at least for a turbo motor, vs the unlabelled one that was in there.

JB3 · #12 11-23-2010, 07:19 AM

Quote:

Originally Posted by funola

Did the thicker Nissen radiator make it run cooler? My Behr is 1.25" thick. How thick are the 2 that you have? I agree with Barry that it is better to run at a higher (reasonable) temp. I have a 92C thermostat that I will be putting in soon. If you're gonna be around at the end of the week we can shoot your head with my gun. I also have a DVM with a thermocouple input we can take temp readings at various parts of the engine.

Ironically, its seems to run a little hotter (as far as the dash gauge is concerned) with the new radiator! Ill have to measure the difference in thickness when Im down there on thursday. Won't be around this weekend though, hopefully I can resolve this by thursday, or ill be using a different car for the weekend.

JB3 · #13 11-23-2010, 07:23 AM

Quote:

Originally Posted by layback40

If the temp is stable at that temp, it makes me think its thermostat related as the thermostat controls the temp under normal conditions.
While its good to run a diesel on the high side temp wise, you run a higher risk of overheat when you load the motor. It has cut a long way into your safety factor. You dont want temps that fluctuate while you drive. A rock steady temp under all conditions is ideal & suggests that your cooling system is in good shape and has plenty of spare capacity.
Does this temp remain the same even when the system is loaded up ( air con, high speed up a hill)?
With another thermostat it should control at a different temp.

The temp remains the same even when loaded, it creeps up a little, but if 105C were 90C it would be acting normally. Ill be able to put in another thermostat on thursday, that got to be it. Its a behr replacement, but maybe its bad, or high temp or something. Ill post back after thats done and see how its running then

barry123400 · #14 11-23-2010, 09:14 AM

I would consider putting your present and replacement thermostats in a pan of water and watching for the opening points. This best preformed with a thermometer in the water as well.

I am at best a part time hobby mechanic so I would also verify the thermostat has been installed in the correct way. Otherwise for example I might just copy the way the last one was installed.

My gut feeling is that the gauge itself is suspect. If there were another 123 type in my possesion or I had a local friend or aquaintence with one. I would extend my gauge wire to his sendor and use a battery jumper cable betwen the two cars to link a common ground. There is so little current even a speaker wire is more than enough.

He would know instantly when his car came up to temperature if your gauge was relativly accurate. You do not want to land up going in circles.

JB3 · #15 11-23-2010, 09:23 AM

Quote:

Originally Posted by barry123400

I would consider putting your present and replacement thermostats in a pan of water and watching for the opening points. This best preformed with a thermometer in the water as well.

I am at best a part time hobby mechanic so I would also verify the thermostat has been installed in the correct way. Otherwise for example I might just copy the way the last one was installed.

My gut feeling is that the gauge itself is suspect. If there were another 123 type in my possesion or I had a local friend or aquaintence with one. I would extend my gauge wire to his sendor and use a battery jumper cable betwen the two cars to link a common ground. There is so little current even a speaker wire is more than enough.

He would know instantly when his car came up to temperature if your gauge was relativly accurate. You do not want to land up going in circles.

This is not a bad idea. the engine in my 240D is still running and hooked up. I actually took the sender out of it as a known good sender as well and put it in the 300D, but I could certainly perform this test if the thermostat did not work. This makes me curious, could there be a difference in temp gauges/senders between the 616 and 617? Would I be able to perform this test on a 240 vs a 300?