'91 300D Turbo (602) continues to run hot... - PeachParts Mercedes-Benz Forum

MercFan · #1 03-12-2011, 04:31 PM

Friend of mine has a '91300D turbo body. He recently replaced the engine in it with a '93 donor engine (almost identical). Anyway, the car had always run hot - even the old engine ran hot until it lost the oil pump chain and died.

Now with the new engine in place he continues to have issues with running hot (around 100C - 105C) on any kind of an incline.

Here is a list of things that he had replaced recently:
1) New water pump
2) Replaced fan clutch with a good quality used one from another car
3) New radiator installed
4) He messed with the thermostat - not sure what, but ended up putting the same one back in...

This is what gets me - he had a new radiator put in and a completely different engine and he has very similar symptoms as before with overheating.

One thing he told me is that the auxhilary electric fans on the front of the grill are not activating (ever). How are they connected (thermostat switch or a relay)?!

What else could it be?!
James

shertex · #2 03-12-2011, 04:56 PM

Quote:

Originally Posted by MercFan

Friend of mine has a '91300D turbo body. He recently replaced the engine in it with a '93 donor engine (almost identical). Anyway, the car had always run hot - even the old engine ran hot until it lost the oil pump chain and died.

Now with the new engine in place he continues to have issues with running hot (around 100F) on any kind of an incline.

Here is a list of things that he had replaced recently:
1) New water pump
2) Replaced fan clutch with a good quality used one from another car
3) New radiator installed
4) He messed with the thermostat - not sure what, but ended up putting the same one back in...

This is what gets me - he had a new radiator put in and a completely different engine and he has very similar symptoms as before with overheating.

One thing he told me is that the auxhilary electric fans on the front of the grill are not activating (ever). How are they connected (thermostat switch or a relay)?!

What else could it be?!
James

I'm assuming you mean 100C, not 100F, right? Anyway, it sounds to me like the car is operating exactly as it was designed to operate (see the owner's manual on this point). 100C on a long upward grade is not "overheating," but a temp well within specifications. At about that point (maybe a little higher?) the aux fans should kick in.

Keep in mind....and for some reason this spooks people....the temp gauge on these cars is NOT an idiot gauge (showing a steady temp regardless of the actual temp), but a gauge that is reading the true temp. When under load, the temp will go up, and this will be reflected in the gauge.

Now, on a long stretch of flat road, it should read low to mid 80's. If it were 100 under THOSE conditions I might wonder if something was wrong.

MercFan · #3 03-12-2011, 06:15 PM

Quote:

Originally Posted by shertex

I'm assuming you mean 100C, not 100F, right?

Right - I made a correction to 100C.

Quote:

Originally Posted by shertex

Now, on a long stretch of flat road, it should read low to mid 80's.

It does run in mid 80s on flat stretches but any incline will quickly send it over 100C and sometimes 105C (on especially warm days).

Why won't the auxhilary fans kick in? They only come on when the A/C is in use. What should we be checking - which relay/thermostat switches?

shertex · #4 03-12-2011, 06:19 PM

Quote:

Originally Posted by MercFan

It does run in mid 80s on flat stretches but any incline will quickly send it over 100C and sometimes 105C (on especially warm days).

Why won't the auxhilary fans kick in? They only come on when the A/C is in use. What should we be checking - which relay/thermostat switches?

Someone with more expertise than I may need to chime in...but I wouldn't be surprised if, when it's a matter of load, the fans don't kick in until 105.

What happens on a long stretch when it gets to 105? Does it then drop down? If so, then fans are coming on.

MercFan · #5 03-12-2011, 06:44 PM

Quote:

Originally Posted by shertex

What happens on a long stretch when it gets to 105? Does it then drop down? If so, then fans are coming on.

No, it doesn't drop down... the only way the temp will go down is when you turn the Heater on... you remove some of the heat and the temp will moderate...

We found this link in the W124 online manual - it talks about the pressure switch for Auxhilary fan:
http://w124-zone.com/downloads/MB%20CD/W124/w124CD1/Program/Climate/83-544.pdf

Could this be a culprit?! It seems more to do with the A/C... Can someone comment, plz.

barry123400 · #6 03-12-2011, 07:22 PM

The radiator you sourced was brand new? Two engines acting exactly the same raises questions unless as mentioned your experience is normal and typical on these.

You can wire in a switch to separatly manually activate the electric fan system. Especially if there is no normal temperature switch that does it when you think it should.

You have a clutch fan and should also check that it is in tip top condition. They are and where a wear item on each of the engines.

Since you did change out engines the fan shroud is present now? Verification of the dash temperature gauge may not be a bad ideal as well. Even though it is probably overkill to do it.

If your fuel milage is lower than normal check for a dragging caliper or two as well. This could make the engine work harder than it should have to. Just feel the temperature of all the wheels after a run for sameness of temperature with your hand or a laser temperature reader. This is how I determine if a caliper needs attention if it is not obvious.

MercFan · #7 03-12-2011, 10:11 PM

Quote:

Originally Posted by barry123400

The radiator you sourced was brand new? Two engines acting exactly the same raises questions unless as mentioned your experience is normal and typical on these.

You can wire in a switch to separatly manually activate the electric fan system. Especially if there is no normal temperature switch that does it when you think it should.

You have a clutch fan and should also check that it is in tip top condition. They are and where a wear item on each of the engines.

Since you did change out engines the fan shroud is present now? Verification of the dash temperature gauge may not be a bad ideal as well. Even though it is probably overkill to do it.

If your fuel milage is lower than normal check for a dragging caliper or two as well. This could make the engine work harder than it should have to. Just feel the temperature of all the wheels after a run for sameness of temperature with your hand or a laser temperature reader. This is how I determine if a caliper needs attention if it is not obvious.

Barry - the radiator was new. The fan clutch was not new but it does act the right way (i.e. it doesn't spin much after you shut it off). The radiator shroud is in place. He did notice a mysterious dip in mileage some time back so we checked all 4 wheels today for drag - but came out negative.

He hooked up a manual switch to the auxiliary fans so he can activate them manually and see if it will moderate the engine temp.

Would like to get an electrical diagram or an explanation what controls the aux. fans turning on/off.

compress ignite · #8 03-13-2011, 07:10 AM

B10/8 (Coolant Temp Sensor)tells the N22 "PBU" (ACC Pushbutton Unit) that the
K9 "High Speed Auxiliary Fan Relay" should "kick on". (Partial Schematic Below)

See:
300e Auxiliary Fan, High Speed

AND

Auxiliary Fan Preresisor Delete?
(It's not a 124.128,But A.D. Explains the "Mysteries".

Jim "F" shows how to use a Resistor to lower the High Speed Fan's "Kick In" temp:
http://www.k6jrf.com/MB_CTS.html

compress ignite · #9 03-13-2011, 07:39 AM

The Low Speed Fan is operated by the TEMPERATURE Switch on the Receiver/Dryer.
(There are TWO switches/sensors on the R.D. The other one is a
"Low Pressure Sensor" for the Refrigerant.
[Prevents Compressor engagement without proper refrigerant Levels] )

The High Speed fans are ONLY turned on by the Coolant Temperature B10/8
mounted in the Incoming orifice of the top radiator hose @ the Engine.

compress ignite · #10 03-13-2011, 07:59 AM

Auxillary Fan relay W124 Japanese '89 update

AtlGator · #11 03-13-2011, 08:45 AM

just to confirm, that is too hot (100-105C) as has been verified for me by a few indie mechanics here. i would certainly have asked that a new thermostat go in. my $.02, good luck.

aka"thedude" · #12 03-13-2011, 08:58 AM

What is the condition of the oil cooler? are the fins plugged with nastieness? Oil plays a part in engine temp as well as coolant. Just a thought

MercFan · #13 03-13-2011, 01:28 PM

Thanks very much Compress Ignite - lots of info to digest and followup with.

As for the other post about the oil cooler - it's from the donor engine - and the engine is sound.

compress ignite · #14 03-16-2011, 04:11 AM

I'm with AG on this.

And How do you tell a GOOD used Viscous Fan Clutch from a Bad One?
(Get a New Clutch!)

OM606 Clutch is cheaper and engages at same temps.

Clutch MB #606 200 01 22 (One Each) [$103.USD]
Fan 11 Blade, composite MB #606 200 01 23 (One Each) [$54.02]
New Bolts for Setup MB # N914020 006017 (Three Each)