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Letter 27

Isuzu Trek Owners Infoletter #27

Mice, K&N filter, Solar overcharge, Air Conditioner controls, Window drain holes, Headlights.

Bruce Matlack writes about several issues, matlackwindsurfing at

(remember you need to replace “at” with @ in our email addresses)

Mice: There are two gaping openings where varmints can gain access, as I saw them with my own eyes during an all-out mouse attack at Baker Lake in Washington state last summer. The heater opening that adjoins the floor below the fuse box/ dash board storage compartment and the 2-inch blower hose from the blower. I put chicken wiring over both. In the rear of the coach where the sewer pipe goes down from the bathroom sink there is a hole drilled with 1/2-inch clearance room all around to afford perfect entry for critters. I foamed all around and embedded steel wool inside the foam first.

K&N air filter replacing stock barrel unit: I notice no improved fuel mileage benefit and, in fact, think I have reduced my mileage. If any one has a stock barrel canister filter assembly they want to get rid of, I’d like to put mine back to stock. An added bad feature resulting from the change is that it is very noisy to the cab area when sucking air at high revs.

Solar panel overcharge: Apparently, there is no overload protection. In the hot and more direct sun of Florida, it appears the panels boiled my house batteries before I knew what was going on. If you do not use your coach electric power, the solar may overcharge the batteries. Turning off the battery switch at the foot well not stop the overcharging. For now I cover the solar panel with something until I can properly solve the problem.

AC/Heater control panel: If you press the button then pull it out, it will shut off the air conditioning system but still allow the dash fan to pull in fresh air from the outside.

Window channel drain hole blockage: During production or later repairs the drain holes in the lower window tracks were covered over, effectively blocking the drain holes. I used a small chisel to open each one. Just because there is a nice fixture on the outer part of the window casing covering the drain openings, do not be fooled! Yours may be blocked on the inside. This has caused a huge dry rot area at my driver’s window siding inside. It is all rotten to the core from the water running inside, instead of outside for 16 years!

Editor Note – replacement tracks do not come with the drain holes. They must be cut into new track so they match up with the outside drain hole. I use a pin router to cut the slots. This is also a maintenance item, checking the drains to verify they are not plugged up.

Headlights: I put in all new bulbs and adjustment screws and then found that the fiberglass mounting frames were too far off for any adjustment screw to compensate. They were installed that way from the factory. No wonder the headlamps were basically so poor, and we read of all these complaints in the Trek letters over the years. I remounted and fiberglassed them in at the correct attitude to be within range of the adjust screws. It took me the better part of 4 days of trial and error until I realized this huge error from the original factory installation. On the Internet, you can find out how to adjust headlights against a wall. Check the mounting bracket attitudes first before going out and buying fancy bulbs!

Trek newsletter solved some problems on the road:

-Total shut-down of AC power with Magic Bed on top of driver’s seat. Reset GFI in bathroom.

-Transmission locked in 2nd gear-would not shift. Pulled over, shut down engine, waited five minutes, restarted and on my way with no further issues.

Miscellaneous fixes :

-Mud flap splash guard in front of the step motor to protect it.

-Use a big clip board with checklist on steering wheel to remind me a second time not to drive away with jacks extended.

-Spraying privacy curtain tracks with silicone spray made a huge difference in their sliding.

-Bad cabin odor was attributed to the wall paper adhesive. Stripped all paper down to natural wood underneath – was a success.

-Installed a fill hole on top of the water tank to facilitate filling from bottled water in an emergency, sealing it with a marine bottle stop plug.

Maintenance manual, valve adjustment, glow plugs, corrosion.

Berny and Martha Cooper (mbcooper at write:

Hi Ken, Thank you for providing all of the info on the I- Trek! I have a 1993 2430 Trek with 136,000 miles on the clock. There have been several problems which I have encountered which are addressed in the I-Trek notes, and some which still are looking for a solution.

I located a chassis manual on E-Bay, which has been helpful. The Isuzu NPR and the GMC W-4 are the same chassis, and the manual covers both. One item which has made a huge difference in cold starting was the valve adjustment. From the first day my Trek was difficult to start, with prolonged cranking and a big cloud of white smoke. The first thing I checked was the glow plugs. Checking them with a multi-tester for resistance showed that one of them was burned out. I replaced it with a new one, but did not see much improvement. It ran fine and no smoke once it started up, and warm starts were quick with not too much smoke.

The manual said that one possible cause was the engine needing to have the valves adjusted. This engine has solid valve lifters, like old cars before the hydraulic valve lifters came into use, and the factory manual says to adjust them every 32K miles. They must not have been adjusted, as the exhaust valves all had no clearance. (The intake valves all had the correct clearance.) It is utterly amazing what a difference a few thousands an inch of clearance made in the starting of this engine! It now starts right up on the first crank with very little smoke! I imagine that my fuel economy will now improve also (average 13 MPG), as the valves must have been slightly open, thereby reducing the engine compression.

One of the problems with this Trek is that it was driven in winter in the mid-west and has suffered from road salt corrosion. There are a lot of rusty-looking steel components around the engine, which do not inspire dependability. I have noticed a recent oil leak around the top of the oil filter. Everything being jammed in the way it is does not allow a clear view of the components, so it is hard to see where the leak is. Perhaps one of the readers has experienced this problem and has the answer?

I “bit the bullet” this summer and painted the rusty propane tank on our Trek. I had been dreading the job, but found that it was not so bad or difficult. I used the leveling jacks to elevate the Trek enough to drop the tank and roll it out from under the body. My hydraulic floor jack let it down gently and was used to install it after the paint dried. I taped off the fittings and level indicator with masking tape, and sanded the rust with some 80 grit sandpaper as preparation for a two-coat brush-on polyurethane enamel. It looks as good as new now! The most difficult part was reaching up from below to loosen (and then tighten) the bolts which attach the tank to the frame. My generator was not working, so I dropped it also and cleaned and painted the mounting tray. The problem turned out to be a corroded wire on one of the big multi-plugs on the left side.

I cleaned a lot of rust scale out of the air filter housing when I changed the air filter. The location of the air filter above the front wheel is not very good!

I have some other questions and some solutions to other problems which I can write about in future. My wife and I love our Trek, even with the problems!

Thanks to Berny and Martha for the input.

Editors note, we still get requests for information on “dash bounce”, the firewall to sidewall attachment problem. Early Infoletters addressed this problem – a quick look at the index shows Infoletters 4,6,7,8,13,and 14 have information.

Fluid lines, camshaft.

Clark sent in the following information (clarkvg

Here is a little info for the newsletter. I talked to a guy who is a tech rep for Cummings Diesel. Prior to working for Cummings he ran a diesel shop for a bread company which had a big fleet (30) of NPR Isuzu-powered trucks. He said he was amazed at how few problems they had with them. He suggests that if you drive your Trek though road salt you should replace all the metal fluid lines as the Japanese steel lines do not hold up. He also suggested replacing the camshaft before or near 250,000 miles. I asked him about the turbo-chargers and he had no problems with them. If anyone has questions for him that we (the group) cannot answer, I would be glad to call him. I’m not comfortable giving out his name.

Thanks to you, Clark.

ACME Air Conditioning/Cruise control, Onan generator.

Ken Harmon, IsuzuTrek at

Update on Acme cruise controls and air conditioning systems installed on the Isuzu Treks:

While traveling around the Great Lakes this summer we made it a point to stop in the Elkhart/Goshen, Indiana, area to see if we could locate Acme or any of their parts inventory.

I had no luck at the former Acme address and at three local RV factory surplus/salvage companies. Apparently Acme has been out of business for about two years now.

When I called the Kansas City number for Acme (913)371- 5373, it rang in the former Acme building but the company name is now Southwest Professional Vehicles (SPV Inc). Cindy Harris works for SPV now but she also worked for Acme. They have some of the old Acme air conditioning inventory for the Trek, Beaver and some other models. She does not inventory the Trek air conditioning compressors but she can get them. Cindy said they tried to buy the Acme Indiana inventory but it was all thrown out at the end of last year including all of the cruise control parts. Cindy referred me to Auto Air Specialists in Ontario, CA, (John Elston, or Rita) (909)988-8458 as another possible source for Safari air conditioning parts.

One of the salvage dealers in Elkhart said they started having difficulty acquiring RV salvage with the downturn in the RV industry. Individuals were going in and bidding on the salvage and then selling it on Ebay and Craigs List as a home business. This could be a source for obsolete parts if you can identify the part and find it.

Onan generator. My initial problem with the generator was hard starting, backfiring as it warmed up and sometimes it would stall under air conditioning start-up load.. I changed the spark plug and it ran better for about 4 hours but the problems returned. Since we were heading to the EAA Airshow with extended dry camping I wanted to get it fixed.

The first two service facilities I talked to said it looked like the entire generator unit would need to be removed from the RV and have the engine disassembled to correct the problem. I paid one facility $55 for their opinion and the other shop had a labor rate close to $120/hr. I started looking for a better option and found Engine Generator Specialists in Madison, WI, 4307 Acker Rd, Madison, WI, 53704, Phone (608)241-2212.

The repairs at Engine Generator Specialists started with replacing the air filter and doing a test run. The filter helped some but the unit still had starting problems. The mechanic asked me what I set the new spark plug gap to and I told them it was right out of the box, I did not check it. They use only NGK P/N BPR6ES set to .020 gap as specified in the Onan Service Manual under the 3600 LPG specifications. (Do not use the .025 gap specified in the Onan Operators Manual) The unit ran better but he thought it could be improved so he checked the valve clearance. I set the valves about two years ago but he found the clearance had changed. The intake gap was less than the specified .002 and the exhaust gap was more than the specified .002 .

I always like shops where they allow you to talk to the mechanics. Stewart Alder, the mechanic that worked on my generator, said the Onan propane generators have very few adjustments but they are very sensitive to having the valve and spark plug gaps set properly. He said the propane units are much more sensitive to proper adjustments than the gasoline version of the generator. He also said the engine needs to “breathe” as well as it can. In other words, it needs a clean air filter along with properly adjusted valves to help pull the propane vapor through the regulator, carburetor and into the engine.

In my case it looks like a combination of three things were not quite right and it added up to one large problem. Each time an item on the generator was fixed it ran better. I will be paying more attention to each of these items on my annual generator service. On our return trip from the Great Lakes area I ran the generator at 500 and up to 10,000 feet elevation in Leadville, CO, and it is running good.

A little more information: The other problem the Onan repair facility sees is oil in the propane. In cold weather the oil can contaminate the regulator and carburetor. Their engine oil recommendations: straight 30-weight in summer to aid in cooling and 15W40 in the winter.