m936A2 no air to fan clutch system

[sweetk30]

so the other week we were playing with the wrecker and she overheated a bit . 2 gal lost from boil over . . let cool down and she seems fine . no loss of coolant since .

well before shut down I popped the hood and the fan was not spinning . we were using the rear pto for the crane / drag winch . rpm was 1500ish and 1-5 gear selection .

so I got a jic to jic fitting #4 to connect the 2 lines and bypass the temp switch in the upper rad hose/pipe to test the system . no good . so I pulled the line at the firewall fitting from the BIG pipe just behind the ether can mount . blew threw it with my mouth and lots of air flow .

so I fired up the truck and released park brake / and tested in gear r & 1-5 no air rush sound with the hose off . also pulled the pipe thread to jic 90* fitting and no crap in it free for air go threw it .

truck lot drives and brakes work fine .

so were do you guys think I should look next ?

 

[simp5782]

so the other week we were playing with the wrecker and she overheated a bit . 2 gal lost from boil over . . let cool down and she seems fine . no loss of coolant since .

well before shut down I popped the hood and the fan was not spinning . we were using the rear pto for the crane / drag winch . rpm was 1500ish and 1-5 gear selection .

so I got a jic to jic fitting #4 to connect the 2 lines and bypass the temp switch in the upper rad hose/pipe to test the system . no good . so I pulled the line at the firewall fitting from the BIG pipe just behind the ether can mount . blew threw it with my mouth and lots of air flow .

so I fired up the truck and released park brake / and tested in gear r & 1-5 no air rush sound with the hose off . also pulled the pipe thread to jic 90* fitting and no crap in it free for air go threw it .

truck lot drives and brakes work fine .

so were do you guys think I should look next ?

The #8 jic line with the 90 on it that supplies that air to that fitting comes from the top passengers side tank with a #8 on it. It is cotton jacketed. That supply has no check valve. Pull it off and see if you have air out of the tank.

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[sweetk30]

o.k. both power switches on & off tested .

upper hose off = no air flow .

lower hose at tank = crack loose lots of air hiss . didn't remove 100% as tank is full psi .

upper air tank under pass side cab = full air and tank drain screw open lots of air .

lower tank under cab = no pressure from tank drain screw & no mud bugs plugging the hole .

3rd and 4th drain screws = lots of air flow when open .

. . .

only thing we did recently was 6 valve cores 1 per tire to not let ctis feed the tires . just have not unplugged the electric or air lines on the unit in the cab controller .

 

[simp5782]

o.k. both power switches on & off tested .

upper hose off = no air flow .

lower hose at tank = crack loose lots of air hiss . didn't remove 100% as tank is full psi .

upper air tank under pass side cab = full air and tank drain screw open lots of air .

If you don't have air at the firewall end of that hose but do at the tank end then its collapsed maybe. Its 1/2" hose. It comes from the tank under the bottom of the cab to that fitting on the treadle valve. Thats all. Be cheapest to pull the line and find the obstruction and get two reusable 8 to 8 collars and fittings and splice it together. Or replace the line. Probably around 75 for that hose with fittings

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[sweetk30]

we have a full hose shop 5 min from were the truck is at now . so if hose is bad then we can get a new one no problems .

well I guess I will go pull the hose and check it out now .

will post back up when I find the problem .

thanks for the help

 

[sweetk30]

o.k. who ever installed the self tap bolts that hold the hose clamps to the body must have a special skinny socket .

so for testing I decided to hand trace out the 2 hoses cause if its bad I am not removing the old one . I will get a new one and a bag of zip tie's and sister it to the old .

well the top port / hose off like I was shown does NOT go to my top tank on the truck . the hoses are flip flopped in there hangers under the cab .

so I pulled the lower tanks empty tanks hose and I blew threw the hose with my mouth 100% flow no restrictions .

....

so did someone install these hoses wrong before we got this truck ? ?

or is there a tank to tank feed problem ? ?

should the 2nd tank be full when the air is up on this truck ? ?

and under normal operation conditions should there be secondary air psi on my dash gauge ? ? ..... currently nothing showing . . . . any air brake truck I am use to has 2 needles and both should be up . so maybe my tanks were plumbed backwards and never correctly working . ? ?

...

I stopped work for now until further info / help thanks .

 

[sweetk30]

so kind of long story here but its fixed for little more than $1.50 for the test fitting and 2hr of my time and a few helpful hints from here .

so I flip flopped the 2 hoses on the tanks . this got me air to the fan system line and sec air gauge working . but I lost primary gauge function . still run/drove in the lot . also still no air from middle drain screw port .

so I flipped them all back the way they were to before I started . then I said there has to be something funky going on here that's stupid simple . so I started tracing the lines out to see if I could find a check valve inline some place maybe . . . well I found something alright and it wasn't a chack valve but a ball valve on a 3rd tank inside the frame rail pass side up high near the BIG pto pump for the wrecker bed .

this tank had 2 1/4 turn ball valves on it and 1 was shut . looked to have been shut for a long time lots of grime and dust on it . as soon as I opened the valve the system equalized and every thing was flowing were it needed to be .

so I drained the whole system and re-fired the motor watching both pri & sec air pressure gauges both fill up now . then once full I hooked cracked the feed / supply line to the thermo switch in the upper rad hose and got air out . also when I first fired the empty system I still had the test fitting in-place and the fan was locked at around 20psi or so .


other than a road test to do yet to get up to temp and check full function it all seems to be normal . I will get a pic or 2 of the valves and post up later when I am home .

 

[simp5782]

Top hose goes to the top of the treadle valve the cotton jacket hose on the primary tank the lower one goes to the 3rd connection from the top NOT counting the one with the fan hookup. Should be directly below that hookup.

Its not a special socket. You take a flathead screwdriver insert it sideways into that hanger and twist to bend em out. Should be two.under the cab and one at the frame.

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[sweetk30]

you must have not read my other posts . . . i figured it out .

but here is the pics of the 2 ball valves on the 3rd tank hidding up inside the frame by the t-case and BIG pto pump .

 

[simp5782]

Thats standard secondary and primary shut off valves
. They also tend to butterfly effect when they go bad. With pressure going thru they will fill and shut, fill and shut then show open. Make sure they arent loose

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[sweetk30]

if so then i will wire / zip tie / tap them open . . . thats crazy . and why hide these so far under the truck when you can get to the 2 tanks under the cab so easy .

 

[simp5782]

if so then i will wire / zip tie / tap them open . . . thats crazy . and why hide these so far under the truck when you can get to the 2 tanks under the cab so easy .

If they are butterflying you need to replace them. They can come apart and a check ball gets stuck in a line and causes issues. It is just a half inch ball valve from any hardware store.

That is just normal off the wet tank to have those valves.

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