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1996 E300D
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133 Posts
Discussion Starter #1
I know this is a somewhat rudimentary request but I want to make sure I am covering all my bases. She seems to be running a little hot and I am wondering if it is something as basic as needing more coolant added. I have an OBDII data logger and the readings I have been getting are a normal driving operating temp of about 198F-202F (92C-94C). When I am sitting in traffic and it is about 95F outside I have seen it get up to 226F (107C) for a very short period of time.

This seems to be a little hot and I was going to de-grime my radiator fins to see if maybe that was the problem. I have the opportunity to clean it good since I have had AC issues and think a leaking condenser is to blame. So I am going to be replacing that and want to tackle this issue too while I am at it.

I got to thinking that I needed to cover the most basic item first though, making sure there is enough coolant in it. I have the correct MB coolant and I always make sure the expansion tank/reservoir is filled to the mark on the tank.

Is there another place I need to check to make sure it has the correct amount of fluid in it?
 

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E320/E250 Bluetec Ford F350 6.7l
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36,470 Posts
No other place to check the level.
Your symptoms would indicate the fan failure. do you have mechanical fan and electric dual fan up front?
The electric fans come only with AC on to my knowledge, so the clutch on the main fan would be my first suspect.
Get one of those infra-red thermometer and track the system temperatures. Coolant pump failures happen even on Mercedes.
 

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1996 E300D
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133 Posts
Discussion Starter #3 (Edited)
So in theory if the expansion tank is filled correctly, then there is a correct amount of coolant in it right?

Both aux fans run and the mechanical runs as well. Although I do not know if the clutch is wearing out. MattL advised me to see how the fan acts on a hot engine right after shutoff. I believe he said if it stops moving quickly after cutoff then the clutch is probably ok. He did say that it wasn't the best way to check though. Any more ideas on diagnosing if the clutch needs replacing?

I also have a OBDII data logger so I can get real time temps. Those temps reported above are what I observe during a 25 mile drive to work. Is there any other way to tell if the water pump may be failing?

Thx
 

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1996 E300D
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133 Posts
Discussion Starter #4
I just had an epiphany...

I took the mechanical fan shroud off a while back to replace the tensioner and never put it back on. Could this be a potential reason it is running hot?? Seems logical since it seems that the mechanical fan could be more efficient if the shroud was on there to enclose the space more...

Thoughts?
 

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'01-E320 & 02-ST2
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31,633 Posts
I just had an epiphany...

I took the mechanical fan shroud off a while back to replace the tensioner and never put it back on. Could this be a potential reason it is running hot?? Seems logical since it seems that the mechanical fan could be more efficient if the shroud was on there to enclose the space more...

Thoughts?
Ah, another mystery that is no longer "shrouded". :rolleyes:

But that is a 10-4, good buddy. The shroud is an integral part of the cooling system. By effectively "sealing off" the ends of the fan it forces air to be drawn through the radiator and condenser instead of around the edges of the fan. Put it back on and you should see a marked improvement.

Take care and enjoy the ride,
Greg
 

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E320/E250 Bluetec Ford F350 6.7l
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Without the shroud the fan is recirculating the air in the engine compartment.
That should give you one answer.
Than again, without infrared thermometer checking it is all guessing. Couple sensors displaying data in the car will not answer that.
 
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