Geoff Weeks

Back when I did my Low-Fow Cummins rebuild, the engine kit (Interstate McBee) out of chassie kit was around $1500 and the re-cored 1500 sq in radiator was $2100! That just doesn't seam like it should be. However I could pull Parley's canyon in the summer with a full load, no problem.

Automotive alternators and generators both produce power to recharge the vehicles battery. Both have electromagnets, neither have permanent magnets. (Some small engines use permanent magnets as do some motorcycles, but the amount they can produce is limited) Modern car and truck alternators all have rectifiers, but they are not separate, they are located inside the case of the alternator, where they can be cooled by the fan. Generators are somewhat limited in their power output. The field is the stationary coil and the power comes from the rotating (armature). The biggest generator generally fitted was a 50 amp unit, and to make those 50 amps, it had to be turning fairly fast. Leece Neville was the 1st to produce automotive alternators, but at the time the only rectifiers were big metal oxide types that had very limiting characteristics. Still, they can produce more power at lower RPM. They had to have remote mounted rectifiers because they were so large and needed a lot of cooling surface area. In most applications the early alternators weren't worth the trouble. In police, fire and tow trucks that might be working at a scene for hours at a time, lights etc on, they were worth it. So they were retro-fitted or installed when the vehicle was ordered. Once silicon diodes were invented around 1960 (late 50's) then the switch to alternators with internal rectifiers became ubiquitous. Before most fire trucks had 120 volt inverters or generators, you could also tap into the AC output with a transformer and run 120volt lights and universal motors for saws and such. Even after the silicon diode, many mfg of large vehicle alternators kept external AC taps for use with a transformer (Delco DN40 and DN 30) as well as various other. In the late 50's Leece Neville sold a "conversion kit" to convert their early external metal oxide rectifier alternator to internal diodes. I did a write up about installing one on my early Leece Neville.

If the wheels turn, but in opposite directions, the brakes are not stuck (at the wheels) but something is preventing the driveshaft from turning. In gear is the 1st thing to check, frozen driveshaft brake, if equipped. Damage in the transmission, all come to mind.

In the late 2000's I had my 1942 re-cored, and the core was still an orderable item. When I had my Marmon re-cored a few years later, it was a "custom core", move forward to a few years ago, and my good semi-local radiator shop is gone.

My wife also will pick them up. We have a fox snake that for the last few years (5?) over-winters in our basement. Cats on the 1st and 2nd floor, decent size snake in the basement, not too many mice, but we still get them? Hibernating snake doesn't eat much.

This is a far cry from "it came apart when I removed it"!

Geeze, that would have been helpful to know! You knowth not what your knowth not! So we can conclude the original was defective, at least in some part. So it was good you replaced it. again a lack of clarity is leading to problems. I am going to walk away, this is obviously way beyond what you can do, and you should either find someone local to come and help you or pay for a shop to work on it.

It looks like you are missing part of the valving on the MV-3

we're going from bad to worse here. I think it is time to call in professional help or someone who knows air system to put another set of eyes on the problem. It is likely something simple, crossed lines, something left dis-connected etc, but before you do more, we need better info then you can provide. Not you fault, you just don't have the experience needed. Mecho,Joey Mack or I can't "see" what is happening and how the valves and air system is from this end of a computer screen. We are working blind, and you can see but don't know air systems well enough. Not a good chance of success. Do you know anybody with more experience that can come and help you?

With the air lines on the trailer hooked up, push the red in and hold it in for 15-30 sec, it should stay in.

Red button will not stay in if the red trailer line is open to air. You need to put a dummy gladhand on to test the tractor. I think, according to what we have read, that it does eventually stay in when hooked to the trailer after holding in long enough to charge the trailer. This is normal, the tractor is not the problem. In all my years on my own equipment I only changed one MV and that was because I couldn't get the gasket to repair the old MV-2 on the truck. They don't go bad that often. I since got a new gasket for the MV-2 and re installed it, kept the gaskets in stock because all 3 of my truck had the same valve (which was why I re-installed, the replacement was a Midland and the rest of the fleet was Bendix MV-2)

Ok, truck is fine, problem is trailer is leaking off. Concentrate on the trailer. chock wheels, start truck allow to build pressure push in buttons a fully charge the trailer until the compressor shuts off (dryer vents) then turn off the engine without disturbing the buttons and watch the air gauges for the 3 psi/min max drop. If it is dropping fast it is a big leak and should be easy to find, if it is dropping slow it will take more work to find.

Ok, if I understand you correctly, the problem only shows when you are connected to the trailer. Please confirm this is so. If the above is true the trailer is the problem, not the tractor. A trailer that completely bleeds off all stored air pressure so every tank in the trailer is at 0 psi, will require briefly holding in the red button when it is 1st charged until the supply line to the trailer reaches the "autotripper" pressure in the valve. This is normal operation. The valve is supposed to automatically pop out if the line pressure is below 25-40 PSI "why did this just start" you may ask? Well you have a leak in the trailer system that is bleeding off all the pressure. Normally it is common for a trailer to bleed down when parked, esp air ride trailers, but there is a valve that is supposed to cut the air to the air suspension and save the air pressure below about 55 psi for the brakes. So how do you determine if you have a big leak, by the DOT pressure test I wrote about earlier DOT pre trip says this is supposed to be done with the pre trip inspection, or by measureing the time it takes for the compressor to cycle back on (blow off to blow off time). I freely admit that I don't do the DOT pressure check on pre trip but rather assess the condition by the duty cycle of the compressor. They both are a measure of how much pressure leaks off in a given time. The DOT method is the one you may be tested against in a level 1 DOT inspection, my method is just a easy way for me to assess the condition of my air system while driving. So called silent leaks can be hard to find, it takes going over everything with soapy water in a spray bottle, looking for bubbles. Sometimes a piece of hose held to your ear can mask surounding sounds and help narrow in on a leaky valve. Braided covered rubber hose can leak along its length and not make a sound but will bubble the entire length when sprayed with soapy water.

These were from page two, It wasn't clear to me or to Mecho that you had disconnected the trailer at that time. We are not mind readers. Your admission that you don't know what the system pressure in an air braked truck is, shows you need some guidance from someone looking over your shoulder until you learn the very basics of air brake systems. Operating pressure and how to check for leaks that can't be heard are very basic skills needed to work on the system. They are also part of the pre-trip portion of the CDL test.

The problem is: he doesn't know enough about air brakes to pass the pre-trip portion of the CDL test, there seams to be no way to get him to clearly answer or follow the directions. Mecho in the 1st 2 replies was trying to get him to separate the truck from the trailer air system to see which it was in. It wasn't until much later on, that he did disconnect the trailer, by then we were well down the rabbit hole because he didn't do what was asked by the 1st guy who tried to help. I mistakenly assumed he had followed Mecho's advice and was digging deep into the truck system, when in fact he hadn't and so I sent him on a goose chase based on what he said, not what he did. Yes, using an inflatetor hose (depending on length) is more or less plugging, but by that time the damage was done. A person who doesn't even know the correct operating pressure of a trucks air system, should not pass a CDL test, never mind work on truck air brakes. Ignorance is not a sin, everybody starts out not knowing stuff, however if you ask for help and are given clear instructions, either follow and report or admit you don't understand or know how to do what is asked. The lack or clarity in his responses likely cost him the price of an MV-3 and the time it took to install. Not knowing the working pressure of a truck air system or how to look for leaks (Something required in a pre-trip) is a clear indication that he shouldn't be working on the brake system without some qualified help right there with him. It is no skin off my nose (or as we used to say in the repair shop "My truck works") but people can get hurt or killed if a defective vehicle is on the roads. Again, everybody has to learn, but you have to be willing to admit your ignorance and ask questions if you don't understand what people like Mecho are asking him to do. Mecho's 1st post was to break the problem in half, the best and most basic diagnosing action. Ignoring it and not clearly saying he didn't do it, wasn't accepting help given freely. You can't learn if you are not open to it.