Fan clutch leaking/slipping

FOURWHL · 02-18-2018, 04:00 PM

Had my fan clutch slip a couple times when it was real cold last trip. Didn’t think much of it. Got worse today as we were climbing I70 out of Denver. Pretty much ran the fan the entire time even tho coolant was at 182F. Then I noticed I was leaking secondary air. I could hear a flickering of psst psst psst and watch it bleed down and then compressor pop it back up. As I drove I noticed the leaking sound seemed intermixed with the clutch going in and out. When I stopped and checked it’s definitely coming from the valve area on the firewall. Don’t see any actual leaks so that’s leaking me to a valve/solenoid. Probably will go over the wiring to the solenoid as it’s in a hole through the firewall with no grommet, but barring that anybody had this happen or have any suggestions?

KRedburn · 02-18-2018, 06:13 PM

Try pushing in toward the valves on the air lines. Do not pull out. These fittings are "push-on" . Maybe one has come loose a bit. Have had this happen many times on OTR truck.

Tugboat609 · 02-18-2018, 07:30 PM

Could be the fan clutch solenoid leaking or going bad. My Peterbilt has one mounted on the firewall and has gone bad twice.

FOURWHL · 02-18-2018, 08:38 PM

Does the clutch engage or disengage with air pressure?

RV Randy · 02-19-2018, 04:31 PM

Quote:

Originally Posted by FOURWHL

Does the clutch engage or disengage with air pressure?

I searched around as much as I could. What I found seems to indicate that if you lose air the fan will default to engaged, which makes sense, works just like our air brakes. Fits your symptoms too i.e. the fan stayed on most of the way even though engine temp was on the cool side of normal range. It was probably excess fan engagement causing it to run cooler.

After reading multiple threads the most common problem seems to be with the solenoid that controls the air to the fan.

From Mobile Diesel Tech:

"To release the fan you require a circuit from the ignition switch through the solenoid and to ground through the FAN CONTROL#1 output on the ECM(usually A2). This will energize the solenoid valve and air will flow to the fan clutch to release it. The ECM monitors the temp sensor on the cylinder head to determine when to send the fan energize signal"

If this circuit is broken anywhere the solenoid will close and the fan will lock. Also if you loose air due to leaks the fan will lock in. Sometimes this is a bad ground through the ECM, try taking the solenoid ground wire direct to ground to test for this"

Me - Of course if the circuit is OK you could have a stuck solenoid not sending enough air to the fan or you have an air leak preventing full PSI from getting to the fan.

Hope this helps

FOURWHL · 02-19-2018, 05:47 PM

Welp I feel like an idiot. Ended up trying coach net as we don't have much time up here for my amateur troubleshooting.

Turns out the electrical connector was loose in the socket. Likely gaining/breaking contact with the vibrations. All is working as expected now. Glad it ended up being something simple even if it did cost me $82

Thanks for all your research Randy. Would've bee. Really helpful had I decided to tackle it. Instead we got some turns in on the mountain so all good!

KRedburn · 02-19-2018, 05:59 PM

Don't feel too bad. On a OTR I had and issue with the trailer lights. Found it was a incorrectly labeled fuse. Cost me 370 bucks for a 1.50 fuse.

FOURWHL · 02-19-2018, 06:17 PM

Yeah money well spent to know we can enjoy our trip and get home safely

joet19711 · 02-20-2018, 08:21 AM

Glad it was something simple, how is the wet bay?

mookieblaylock · 08-13-2018, 09:41 AM

Apologize for bumping an old thread, but on the past couple of trips I noticed the following symptoms that sound very similar to what you described:

1. The fan clutch has been coming on way more frequently than usual - sometimes even at temps at or below 150 degrees.

2. I can hear what sounds to be like a small blow off valve letting off air just before the fan clutch engages. This sound appears to be coming from the driver's side of the engine bay at or near the firewall.

3. The secondary air system is losing pressure at a significantly higher rate than the primary system while driving down the road.

All of this made me recall this thread from a while back. I was wondering if you could tell me which electrical connector ended up being the culprit in your scenario?

Thanks,
JT

FOURWHL · 08-13-2018, 10:32 AM

Look on your firewall above the drivers side tire. That’s the solenoid that activates the fan. It dumps the air to activate the fan. What you’re describing does sound very familiar.

The connector is at the very bottom of the solenoid /valve. Could only see it when standing on the ground (not on the tire which is how I missed it)

I won’t be at the coach til this weekend when I can grab a pic. If you can take one before then I can better point to it

mookieblaylock · 08-13-2018, 10:40 AM

Our coach is at the house currently, so I'll check it out this evening.

Thanks for the reply!

mookieblaylock · 08-14-2018, 08:57 AM

I found the solenoid in question, but it seems like the electrical connector was solidly connected. I did pull it and reconnect, but I don't think that was my issue (assuming I actually have one). Going to post a pic just for documentation sake. I'm not sure why it's rotated 90 degrees counter clockwise...it's not like that on my phone or computer. Anyway, the yellow nylon tubing is the supply from the adjacent manifold, and the purple nylon tubing feeds the air chamber behind the fan.

FOURWHL · 08-14-2018, 09:37 AM

That looks like it, I’ll take a pic of mine this weekend just to confirm.

The fan should run constant when you unplug it. One more thing I guess you can try to troubleshoot. Could also be the solenoid crapping out.

mookieblaylock · 08-14-2018, 10:21 AM

Pretty sure that's it...I'll pull the plug and make sure the fan stays on 100% to confirm.

After thinking about it some more, the couple of times I really noticed it, it was extremely hot outside...like around 100. When we drove it home last Friday afternoon, it had rained nearly all day, the temps had dropped to around 73, I didn't hear the solenoid blow off or the fan clutch engage, and the secondary system leaked down at a rate much closer to that of the primary system.

Wondering if it's working correctly, and the ECM is detecting higher (or more quickly rising) temps than can be registered on the in cab water temp gauge. I'll fiddle with it some, but I've got to get it to Freightliner to have an ABS issue seen about...might just mention it to them and see what they say.

Thanks again!

FOURWHL · 08-14-2018, 10:40 AM

That all sounds plausible. When it’s working correctly that solenoid will dump air to let the clutch engage. If you’re seeing repeated fan use due to high temps that definitely sounds plausible. I know my fan use goes way up over 90 degrees. Crossing Wyoming it ran a ton and I think my secondary air was off a bit at times. The compressor always kicked on as it got low.

When I was having this issue it was happening where the fan would go on/off for less than a second. That really dumped air as every cycle it would purge.

FOURWHL · 08-14-2018, 10:41 AM

Also may want to grab a scan gauge so you can get a digital readout of water temp

mookieblaylock · 08-14-2018, 10:49 AM

Quote:

Originally Posted by FOURWHL

Also may want to grab a scan gauge so you can get a digital readout of water temp

Good tip. I've got one...just don't have water temp as one of the four main screen gauges. I'll swap it in while troubleshooting.

FOURWHL · 08-14-2018, 10:54 AM

Even better. Yeah once I figured out what the stupid suffixes meant I line having water and trans temp displayed instead of the gauges

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