Engine Fan Problem

layoutshooter · Apr 2, 2008

My engine fan has decided that it should turn it self on anytime I turn on the AC or defroster. It makes no difference what the outside air or engine temps are. It will continue to run for as long as 45 minutes after I shut off the air. I thought it might be the pressure switches/sensors on the AC. I had them checked, both the high pressure and low pressure sides are giving correct readings. I have a 2005 MBE900 450HP. I have been told that it could be a problem with a EGR sensor or some other sensor that I cannot remember the name of. Has anyone else had this problem? If so, what was it? I also found out today that the engine has a recall/modification on it for a freeze plug problem. Do people check on recalls every so often on your own or is it Freightliners job to inform you of these things. I checked 6 months ago and the was no outstanding recalls, or at least that is what I was told. Layoutshooter

LDB · Apr 2, 2008

I've got the same engine and the fan kicks in whenever the a/c compressor comes on as well. It doesn't run nearly as long as yours does though. Once I get up around 50mph it cuts off fairly soon, at least with temps no higher than the 70's. I don't like it coming on as often as it does because the fan eats 25-30 horsepower and doesn't need to come on with the water temp at 150 and outside temps pretty low. I wish it wouldn't come on until the temp was up to maybe 165 or so.

greg334 · Apr 2, 2008

This is programmed in the ECM, there are a few things that are measured on the engine and then if they meet the ECM's criteria, the fan kicks on. Happens to me all the time.

OntarioVanMan · Apr 2, 2008

greg334 said:
This is programmed in the ECM, there are a few things that are measured on the engine and then if they meet the ECM's criteria, the fan kicks on. Happens to me all the time.

Don't they have a gizmo to re-program the ECM???

layoutshooter · Apr 2, 2008

Yea, it is really hurting my MPG!!! One tech said that a re-program of the paramiters might help. My truck is running cool as well, even when the fan is not running. I was told it is time to change the thermastats. Layoutshooter

greg334 · Apr 2, 2008

Well that is one solution but I don't know.

My fan kicks on and it is off in less than three minutes. It seems to come on when I am going up an on ramp, or on a hill waiting for a light or basically the worst time to take HP aways from me.

Oh also it really does not take that much away from my fuel mileage...

layoutshooter · Apr 2, 2008

When my fan is operating normally it has little effect on the MPG, BUT, when running 24/7 it really kicks it hard. That 25-30HP is a noticable loss too. This just started about 3 weeks ago. Before that it would only come on when the engine temp got too high. Then it would run for 3-5 minutes till it cooled it down. Have to find another shop to look at it. Will most likely have to go to a Freightliner or Detroit Diesel. Will try to combine that repair and the recall so I don't have to shut down twice. Layoutshooter

davekc · Apr 2, 2008

I would be more inclined to go to a Detroit Deisel dealer. They can also reset some of the parameters on the ECM in addition to checking out the EGR and the thermostats.

greg334 · Apr 2, 2008

I agree with Dave, but it sounds like the same thing I had to deal with, a bad temp sending unit.

layoutshooter · Apr 2, 2008

Sounds like a good idea, most of the Freightliners I have been to have been less than exciting. Only been to one Detroit Diesel, they were great!!! We shall see what happens.
Layoutshooter

arkjarhead · Apr 2, 2008

I drove a Pete once that had a switch on the dash that would allow you to turn that fan on, off, or set it on auto to kick on by itself. That's what you need if you could get it layoutshooter. You'd just have to remember to keep an eye on that temp gauge if you had it in off mode.