Truck#1

Excuse my ignorance. Is the foot valve behind the firewall ( on a CH) that has a half dozen or so air lines connected to it??? If that is it...what does a replacement cost and how hard is it to replace??? thanks. rob

I appreciate everyone's help. The problem turned out to be the unloader valves. I installed a new kit once and had problems because I never scraped off all the old gasket and I used a RTV sealer (a big no-no). So another new kit ($11) and I'm good to go. Thanks again guys. Rob

Ok, you guys that thought I had a head gasket issue I did concur for awhile anyway. I don't know if this make sense, and maybe it still is a head gasket issue. My truck (98 Ch w/427, Jake) does some funny stuff. I had the heater on all day today. I had no recovery bottle / anti-freeze leak. Before I continue know this.....it looks like there are 2 different heater cores going into the firewall..one on top of the other with 2 in 2 out heater hoses. I'm not sure what is what however the bottom core was disconnected by the previous owner. and the hose lines re-routed all over the place. I have heat out of the the defrosters (on the heat setting) and out of the vents on the vent setting. No heat down below. I also get what sounds like an air leak from the climate control levers. I hope this is the cause of the pressure in the system. My question is this...is there a schmatic diagrahm for heater/coolant lines ? I should take a pic and let you guys see the coolant lines under the hood. Thanks again Rob

The wheels aren't locking up and it is an abs system. No rush of air either.

It has 584,000 + miles on it. The only work that was done to it before I bought it was a new cam at about 500,000. Thanks for the ideas. Nothing is ever easy is it???

I don't get much braking with moderate pedal pressure but then all of a sudden they grab like a S.O.B. (almost puts me through the windshield). It's the same with or without trailer. What should I look at??? The brake valve assembly on the firewall? I'm just guessing since I don't know. Thanks for your help guys. Rob

I have a problem with anti-freeze squirting out of the small hole in the plastic cap on the recovery tank. It seems like the system is over pressurizing the top tank, forcing down into the recovery tank then out the weep hole. At one point I'll have a full recovery tank, and an empty top tank ( then I get the warning lights and the engine turns it self off). The engine runs at normal temp and it won't suck anti-freeze back up from the recovery tank. I'm going to replace the cap on the top tank but other than that, anyone have any ideas???? A thought crossed my mind about sealing up that small hole but I didn't. I know it's there for a reason. It is a 98 CH w/427. thanks for your help. rob

I did 1 better. I talked to a Bendix tech. He said it was "Flat Tires" fault.

.....continue. I concurred with Glenn and thought my new air dryer was defective so I took it back and got another. The new one is kind of doing the same thing but not quite. It charges up to about 125psi, the purge valve spits, then it ticks like a bomb. But the ticking is related to engine speed. The higher the rpm's the faster the ticking and it almost sounds like a machine gun. It will tick until the red needle (what tank is that???) drops to 100 psi, the ticking stops and the compressor kicks in again. This is different form the old dryer (which was brand new) That one would tick and then just hiss air continueously. I did put a new unloader kit in the compressor (with the last air dryer) but I had a small problem with the gasket leaking under the cover. I took it off and sealed it with gasket sealer (I was desperate). I did notice the front piston seemed to be stuck in the hole. The rear one popped up when i took the cover off. This is the AD-SP dryer. Any more help would be appreciated. It is a 98 CH with a 427 by the way. Thanks in advance, Rob W.

My bad ...it's AD-SP

The part # on the box is 745 800887 it says AP-SA Bendix air dryer it doesnt have a number after AP. I'll look on the air dryer itself on Monday. The old one doesnt say either. The new one does have a plastic flapper on the bottom. So what you guys are telling me the air dryer is probably the problem and not the compressor or unloader?? It's still under warranty. Also the Mack dealership said I can bring it in and they'll test it. thanks again Rob W.

There is one thing i forgot to mention...when i put the new unloader kit in I had a problem with the gasket leaking and took the cover off again. I did notice the piston on the left side popped up with the new spring and the right one (the one to the front of the truck) didn't pop up and almost seemed stuck in the hole. I did grease the new ones up with the grease in the kit before i put them in.. Was it supposed to pop up when i took the cover off????

The air is coming from the valve or hole at the bottom of the dryer. I dont recall what model Bendix it is.

My engine oil runs almost 200 degrees. Its a 98 CH w/ 427. I do local semi-dump work and today it was about 55 degrees. is that normal?? My 2nd question is this.....my fuel tank is hot. The fuel tank was almost too hot to touch today. I know the return line was pretty hot today too. Why is the fuel so hot?? I didn't put any fuel in so it wasn't fuel from the gas station. Third and final question......My system malfunction light would come on, the engine would idle higher about 800-900 rpm, the light would go off and the idle would kick back down. Any quick diagnosis? Bad sensor somewhere?? Thanks for all your help guys. Rob W.

I have a few issues guys, (not all under this topic) so bear with me. My 98 CH makes a loud clunk when turning left or right. Not all the time but definately with a load on. Driving straight on a bumpy road ....there are no clunks. It seemed to get worse as the day went on. I looked under the truck and can't find anything wrong. It has been greased . Any ideas?? Thanx Rob W.

My 98 CH has Eaton tandems...the front drive is leaking oil at the top of the housing. I origanily overfilled it by accident when i changed oil but i drained off the excess of course it still leaks. I thought it was an odd place to leak almost as if it was under pressure. I understand that my overfilling might have caused this but the previous owner had burned out the bearings in that axle so i dont know if there is any relation. Any thoughts? Thanks in advance Rob W.

OK gang i still need your help. I installed a new unloader kit in my 98 CH. It didn't really make much difference but my air dryer is doing silly shit. It is a new dryer from the Mack dealer....When i start the truck with 0psi its fine until the dryer spits at about 125 (sometimes 130) then it ticks like a bomb for 5 seconds then it hiss's air until the red needle is down to 100. Air builds back up (dryer still hissing air) until it hits 125/130 again. Then it starts over. It seems to hiss air all the time and the compresor is just doing it's normal thing. Is the new dryer bad?? The parts guy at Mack said they are really never bad out of the box. thanks for the help Rob W.

My Jake won't switch to the "high" setting. I can turn it off and works good in low but when i switch to high it stays on the low setting. I replaced the dash switch (with no change)but don't know what else to look at. Any ideas? Thanks in advance. Rob W.

How often should I change my trans and rear axle oils??? I'll do about 15,000 miles a year. The book says about 500 hours (dump/local work....thats what i'll be doing with an occasional trip out of state. I have Eaton axles and trans and require synthetic oil. That stuff is like liquid gold $$$$$$. The 50w synthetic bucket says its 100,000 mile oil. I don't want to change oil too often if its not needed. Thanks in advance

Thanks for the help Thad!!

I installed a new air dryer on my 98 CH. Right after it spits it sounds like air is leaking from the compressor but only for a few seconds. Why does it do this??? There doesnt seem to be any leaks around the compressor. Also the compressor charges my system up to 130PSI. Is there a way to dial it down???? Is there any special way to install the air dryer besides mounting it and connecting the 3 air lines and plug.? It was pretty simple...but almost too simple. Thanks for your help. Rob w.

Has anyone replaced their turn signal housings ( you know the ones mounted under the cab doors) with LEDs? if so what brand and model number. Are they a direct plug-in?? How do you like them?? Thanks Rob W.

Thanks Midnite!

What grade oil is used for the front hubs (non-driving axle)?? The Mack lube manual doesn't say. Thanks.

Bri You should talk to Flat Tires Pauley. He can help you out.