Fan clutch.
 

I have a fan hub/clutch, that leaks air. can hear it hissing air. I put some soap & water on it. it leakes pretty good. I thought. A fellow truck driver looked at it & said, it is nothing to worry about. that he has seen even new or rebuilt one's leak. $550.00 for a rebuilt horton & $175.00 labor. is this a serious problem or just another airl leak, like many others?

Failed fan clutch can make your motor overheat and you can end up with a big time bill...

CHANGE IT !!!!!!!!!!

thank you.

I'm not understanding how a fan clutch that leaks air can cause the engine to over heat.

I help change a fan clutch on an M11. Or was it an N14? I can't remember. But it was a bugger. Not much room to work without taking the rad out. IIRC, we cut a section of the fan shroud out so we could remove the fan. With the fan out of the way, there is room to work. Then we pop riveted the piece of shroud back in place.

Me, I don't like air leaks. I figure every time that air dryer sneezes, my compressor dies a slow death.

I dont know how it affects the temp. my main concern is the leak won't leave me stranded somewhere. the other driver said it will not. & if the leak got real bad, all I had to do was, plug the line going to the fan hub & that would stop the leak until I got home. I am most positive this leak has existed for quite some time, due to my tank's losing all air in 3 hours, when truck is off. I have soaped every air line & fitting I could find, but tcould never find a leak other than a real small one here & there, then yesterday my son heard it from about 3 ft in front of the truck. ( I have real bad hearing) soaped it & bubbles everywhere. my air dryer sneezes every 10 second's. could this leak cause that?


when my dryer 1st started popping off so frequent, i was told it was the govener. put one on, no difference. told air dryer, put new one on, no difference, told air compressor. put one on, no difference. been sneezing for 2 years. had in shop. no one can tell me why it pops off so much. cost too much already by process of elimination & still got the problem. the only thing I can say is everything I had replaced had over 1 mil miles on it, so it probably was at the end off it's life anyway. I just wished 1 of the things I had replaced fixed the problem. downtown, cost me the most.

I would replace the fan clutch as soon as possible. I don't like air leaks, either. You don't want to wait until it fails completely. Worst scenario, if it comes apart it could damage your radiator and and hood.

First of, any audible air leak will put you out of service.

A fan hub leaking air like that will run the fan all the time, and fan hubs can wear out so much they start falling apart, so ya, it should be fixed asap.

Any air leak can make your compressor continuously load or frequently cycle over and over.

Air dryer sneezing every 10 seconds... I would have changed the easiest and cheapest part first.

Those pop off valves on the bottom of the dryer screw up all the time, very common and could cause your problem with the air drier.Very common in my enviroment. (dust, dirt, ice, etc.)

Sometimes they sound like a rattle snake between sneezes and sometimes they just purge air between sneezes.

Really easy to change out, last one I seen was just a snap ring holding the spring/plunger assembly in.

I did change entire air dryer it came with the everything in tack. I know about the bottom valve. it had a constant leak years ago & I replaced just it. that fixed the leak, but that was easy, you could see & hear where the leak was coming from. but this last time, I replaced whole dryer. I forgot about the d.o.t. last time I was stopped the officer stood real close to my grill to get a good look at my windshield, to look for any crack's. anyone that close would hear the air leak, cause I have a cab over, & you can get real close to the front end. I will say as of now, my fan does not run all the time. reguardless. I am ordering part tomorrow & will have on asap. thanks for the advice folks.

Based on your diagnosis, it sounds like all you need a minor rebuild seal kit.

If it's a Horton fan clutch- there are two threaded holes on the housing. You might want to make sure you have two grade 8 lockout bolts handy. If the clutch goes out completely you can screw in the bolts which will kept the cooling fan engaged 100% of the time. Your MPG will go down, but at least you won't overheat your motor.

It's been a few years since I rebuilt mine. Think I paid about $70 for the seal kit, which is nothing more than a few O-rings, some hi-temp grease and a new Sentry safe plug. Took me about a half a day, with basic tools.

You probably have multiple problems, and you might have solved a few of them already. The fan clutch will only get air while the engine is running, so it is not a "loss of air while parked" problem.

You've covered a lot of fittings, but have you really hit every single one? What about the fittings in the dash, on ABS relay valves, on top of the transmission, on the firewall, etc..

After that absolutely cover every single air bag. I once had a hole right in the middle of one. Couldn't hear it. You also have to check exhaust ports on all the valves, as well as the arms coming out of leveling valves. Another possibility is the quick drain cocks on your air tanks. Sometimes they need to be snugged a little more.

As far as your air dryer pissing off every 10 seconds, that's a serious problem that should be addressed. Are you losing enough air pressure during these 10 seconds (say from 120 to 100) to cause your air compressor to turn on or are you barely losing any air? If you are losing that much air you need to get it fixed. That could put you in serious trouble, plus air dryers can only handle a compression event every 120 seconds or so.

If it's not an air leakage problem, it may be the governor, air dryer or the air compressor itself. There are valves in the air compressor that can bugger this up. Look closely for any leaks on the lines going to and from these 3 items.

IMO you should absolutely get rid of ALL quick disconnect fittings and replace them with compression fittings. That's what I'm doing. I've finally got my truck to compress every 20 minutes or so. It's been a battle. I've probably changed about 20-25 fittings so far, and I'm just going to change the rest(some of them cannot be changed to compression fittings due to their design, blasted Volvo!).

After all this is done (checking all fittings, valves, relays, drain cocks, sensors etc..) you have to look at air actuated systems that could possibly drain internally due to bad seals, like transmissions. I've heard of the range splitter actuator leaking right into the tranny.

I have replaced all air bag's. all fitting's are good. yes dash valve good too. replaced ALL, valve's like on top of rear going to brake line's, the 2 under the 5th wheel & the one in the front under the truck, plus all air lines going to tran's & shifter knob, e.t.c. the fan hub does leak when truck is off. I thought key had to be on also, for it to leak. truck off, it leaks. had 20 year mechanic/ o/o look at it. he said it was the fan clutch/hub. looking at the bendix air dryer trouble shoot websight. it told me where to look for my leak based on my symptoms. as far as the constant purging, it does not show lose on dash gage. it stays at 120 & does not drop unless i use brake's. then drop's normally & then right back up to 120.I also have no quick disconnect fitting's. all compression. I have taken dash apart, I crawled under truck from fron to back, checked all possible place's for leaks. when I soaped the fan hub, it really bubbled up. I ordered one yesterday the 25th. has to come from MN. should be here by thurs, will have put on fri, if all work's out well. I am a serious preventative maint person. I change belt's every year reguardless of look's. just like the air bag's, after so many miles or years, it get's replaced. I appreciate the info Allan. I have done all you recommended, & rechecked those parts that was replaced again, & again.

The small line going to your air compressor is losing its charge, that is causing the compressor to compress very quickly, but you have a quick decompression since the governor is hitting the psi limit(that you were at anyways). Make sense? The small line is the signal line, it's leaking somewhere.

BTW if your fan clutch is leaking while off, it may be the air actuator is internally leaking as well.

No! does not make sense. I am not smart enough to understand what you are saying. the small line is leaking? the 2 lines that are connected to the govenor are the same size. I understand I have a leak somewhere. your thought it is in the small line going to compressor? from where to compressor?

I'm sorry I've never been good at explanations. I'm not 100% sure where that small line goes to. But I do know that it controls when the compressor pumps. If there is pressure the compressor stops pumping, but with no pressure in the small line the compressor will pump. So what may be happening is this line loses pressure causing the compressor to pump. But since you're already at max pressure, the governor kicks off right away. Then in a few seconds the line loses pressure again, causing the compressor to pump again, etc..

It either goes to the governor or the air dryer. Either there's a leak in the line, fittings, or at either end(internally in the compressor for example).

What you could do is splice into this line and put a pressure gauge on it to see what happens.

I wish bob h was around he'd be a great help.

I beleive I can grasp that concept. thnak you.

great info on clutch, & dryer.
 

Great info here on the fan clutch, & the bendix ad-9 trouble shoot guide


http://www.bendixvrc.com/itemDisplay...ocumentID=2568


Remanufactured Fan Clutches and Rebuild Kits



the short video on the clutch is informative.

Fan clutch in. $495.00 for part, $175.00 labor to have put on. prices varied from $675.00 to 495.00 the one I got came from kit masters. thanks for all who gave advice.

Really?

Try removing the fan from the hub and set it inside of shroud (place cardboard or something between fan and rad to protect). Then, unbolt fan hub bracket and lift unit out using the fan drive belt. Rebuild hub on the bench, then reinstall.

Back when I had my own truck, I had to re-do the fan clutch twice. The seal kit to take care of the air leak is fine, but as long as you have it apart, I would replace the bearings as well. Hope that came with your kit. I didn't replace the bearings the first time, but decided that since I was getting into it the second time, I got the bearings too. Boy, was I glad I did. The inside one was on it's last legs.

I got the whole hub. not the kit. I will say this was a major air leak. before with both air tanks full 120 p.s.i. with truck off, in 3 hours tanks would be empty. now after truck off for 20 hours, air lose, 15-20 lbs max. this was an overlooked, overdo fix.