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Letter 26

Isuzu Trek Owners Infoletter #26

April 2010


Mikey (yxam2001 at sent some information about microwave repairs.

I was just reading about someone needing microwave repairs on a Trek. I have a 28-foot, 1994, and last year my microwave stopped working. I went to Goodwill and got another one for $12, took it apart and put the tube, capacitor, and diode in mine. I saved the transformer for future needs. My micro was again a fully functioning unit. Note- the used one from Goodwill was not of the same make, nor was it a convection oven type. The parts in these things are almost all the same although the power level might be a little bit different. One caution: when dealing with these things it is always good to ground out the capacitor before doing anything else – it can KILL YOU!

Thanks, Mikey, we appreciate the input.

See the Editor’s note at the end of this Infoletter.

 Brake system repairs (and alternator test) from Dick Kreutzer (rgkreutzer at

I recently experienced brake problems that were a bit puzzling at first. On my return trip from Quartzsite I had two instances of the front wheels locking up and the rear wheels seeming to have little braking effect. After sliding into a couple of intersections in the rain I knew I had a problem.

I disassembled the master cylinder and even after inspecting the parts with a magnifying glass could find no indication of a problem. I have replaced a lot of master cylinders and the problem is usually obvious when the master cylinder is disassembled.

Since the master cylinder looked new I reinstalled it. The other suspect was the brake proportioning valve. After a little research I concluded that it is not just a simple height sensitive valve as used on many vehicles as it has both front brake and rear brake pressure applied to it. To test the valve requires two recording pressure gauges. The price for suitable gauges was reasonable on E-bay and I made adapters to fit the bleeder screws and the master cylinder and installed recording needles in the gauges.

The first test was of the master cylinder and the results were surprising. Every dual master cylinder that I have had fail began to leak down under light application, like when sitting at a stop light and the pedal slowly sinks. The Trek master cylinder was fine until the pressure reached about 250 psi and then the rear section began to leak and the rear piston would hit the front piston leaving only front brakes. That solved the problem of what was happening so I ordered a rebuild kit from FMI and installed it. The next step was to find out why the warning light did not show that the master cylinder was not working correctly. The result was finding that the Trek does not have a differential pressure switch. Vehicles over 10,000 lbs. GVW are not covered by that requirement. Do not expect the brake warning light to indicate any problems other than low fluid or that the parking brake is on.

Using the gauges I determined that the proportioning valve was working within specs. so the Trek is ready for the road again.

Dick Kreutzer 1993 2400

Thanks, Dick, for the brake system input. Dick is very knowledgeable on the Isuzu Trek and I always enjoy talking with him. At the Quartzsite rally he passed on some additional interesting information on the Trek alternator system:

While you are driving down the road if you want to check to see that your alternator and alternator circuit are working properly just move your heater/air conditioner blower switch to the ‘high’ position (all the way up). If the high blow works, the alternator is working. The reason for this is the blower high switch position controls a relay. When that relay closes it connects the blower through a trip-free circuit breaker, a common post on the battery isolator and directly to the alternator. The other blower positions get their power through the ignition switch and instrument panel by way of the chassis battery system.

To trace out this system while looking in the front ‘hood’ (facing aft), look about one foot to the left of centerline and you will see a rectangular block with some circuit breakers mounted horizontally. The stack of circuit breakers will have studs on each end for attaching wires. The bottom breaker is the one for the high blower circuit.

Thanks again, Dick, for some very interesting information.

 Floor, generator and brake repairs, Keith & Jody Redfern (kjredfern at wrote:

Dear Ken & Cathy, we wish to thank you for publishing the Isuzu Trek newsletter. I have owned our 92 trek for 4 ½ years, 2 of which I spent rebuilding & remodeling the interior & running gear. The longer I own it the more we love it. We have come to realize the unique qualities of the Isuzu models. The later models we have looked at have some of the features & qualities of the I Treks but they are a very different vehicle.

When we got ours, we also purchased the factory manuals from for the exact chassis our coach was built on. The manuals have made it possible to do extensive repairs & maintenance on our own & for a local truck repair to have when doing work that requires their doing it for us. Our Trek is a 28-ft that has a rear bedroom that had hidden floor damage under the bed which required tearing out the entire floor & installing a new one. We had to engineer a way to attach the new flooring to the perimeter due to the way the original construction sandwiched the flooring between 2 box members that could not be removed. We devised a way to attach angle steel supports around the perimeter to support the floor. The details would be a lot to relate & nobody else may need to know, but if someone should need help we would be glad share the information. We also built a convertible dinette & replaced the table & chairs which gave us another bed & storage space under the seats. Outside we installed a ladder on the right side which has made a difference for servicing the roof whenever we’re on the road.

When we bought our Trek it had propane injection installed which proved to be a great asset. I had read Dale’s evaluation of propane injection & we were concerned about engine damage. However, we have driven our Trek about 20K miles with no sign of any problems with the engine. We have used the system on hills which has improved performance greatly. It makes a positive difference.

We had a problem with our Onan generator backfiring when running, sometimes clearing after spraying it with WD40. We removed the generator & replaced the magneto unit only to find that the spark plug boots were allowing spark leakage & were the problem. We were able to use Ford distributor boots in place of the old boots after modifying the shroud seals. We also rebuilt the brakes completely & removed the rear brake height pressure regulator after seeing that there was very little wear at all on the rear brakes. After doing so, the brakes worked perfectly now that our front brakes are sharing less of a load than before. We have driven about 3500 miles in the mountains of NY, NH, & VT since with better braking action. We hope that sharing our experiences with our fellow I Trekers helps to preserve the best Treks ever built. The best part is the 13 to 15 MPG.

Trekers Forever, Keith & Jody Redfern.

Thanks, Keith & Jody, for your input.

 High mile chassis maintenance checklist, Ken Harmon (IsuzuTrek at

In case your miles are pushing up there over the 100,000 mile point and your Isuzu service manual chassis checklist is running off the page, I have attached two of my higher mileage checklists. We have over 220,000 miles on our rig so I will be needing a new page soon. Attached are two Adobe pdf printable files: the first is a printable pdf sheet that will take the chassis from 110,500 miles to 227,500 and the second file covers 234,000 to 351,000 miles.

Editor note- we have talked about microwave, brake and propane injection systems in this Infoletter. When you modify a system, you become the design, test and safety engineer for that change. Let’s be careful out there.

High Mileage Check List

High Mileage Check List – 110.5k to 227.5k


High Mileage Check List – 234k to 351k


To print the drawing or see a larger image, click on the PDF link below the picture.

Click here to download free Adobe Reader if you don’t already have it.