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RV Tech Savvy: Parking Brake Problems

Originally Published in MotorHome Magazine

Red letter Q
We have a 1998 32-foot Itasca Suncruiser on (I think) a P30 GM chassis. The emergency brake has malfunctioned (our model is connected to the driveshaft). We have been unable to find RV mechanics with experience, or even Chevrolet mechanics in our area, who know how to repair a model this old. Can you recommend anyone in our area who can help with this problem?

Robert King | Tulsa, Oklahoma

White letter A on teal backgroundThese systems are known as the J71 AutoPark Brake and have a reputation for being problematic. There are several problem areas including hydraulics, switches and other controls, but when properly set up and maintained the brake can provide satisfactory service. One excellent free online resource with photos and text is by Roger Haag (aka oldusedbear) in Bookings, Oregon (www.rvautopark.com). He also sells some parts. Another good source of parts and info is Ultra RV Products in Centralia, Washington (800-417-4559, www.ultrarvproducts.com). Most of the work can be done by a DIYer. I don’t know of any such shops in your area personally. However, typing “The Best 10 RV Repair in Tulsa, OK” into the www.yelp.com website brought up some shops with good reviews. You could also ask the Ultra RV folks if they can recommend shops around Tulsa.

Freshwater Antifreeze Contamination

Red letter Q
During a recent winterization of our 2000 37-foot National Tradewinds 7370, my helper and I managed to pump about ½ to 1 gallon of Walmart RV Antifreeze into my motorhome’s freshwater tank (it holds 90 gallons). How do I wash this antifreeze out of the freshwater tank come spring? Flush with some bleach and/or peroxide? Anything else? Should I worry about RV antifreeze contamination?

Don Feltner | Via email

White letter A on teal backgroundWhen it comes time to sanitize the system, add enough water to fill the tank along with ¼ cup of plain household bleach for each 15 gallons. Turn on the pump and run water through the entire plumbing system, including the water heater and washing machine plumbing, until you smell the chlorine. Leave that in for at least four hours to kill any germs. Then, drain the freshwater tank and flush the system with clean water. When filling again, throw in the contents of a box of baking soda and flush again, if the chlorine smell bothers you. The baking soda will freshen the taste of the water. You can also use a product like Camco’s TastePURE Drinking Water Freshener. Don’t use peroxide. Antifreeze for potable RV water systems is designed to be nontoxic, so small remaining traces of it won’t be harmful.

Backfiring and Power Loss Cured

Red letter Q
I have a 1996 motorhome on a P30 454 Chevrolet chassis, and the dealer and others said the backfire and loss of power under load problems I was experiecing with it was a fuel filter and/or weak fuel pump. I eventually figured out that the problem was burnt and melted spark plug wires. It gets so hot under the doghouse that the wires melted and started to short. It can happen within as few as a couple of hundred miles even with high-quality wires. It’s easy to see; simply run the engine in the dark and look for sparking at the plugs.

The eventual solution was to install silicone high-temperature racing spark-plug wires and boots. Problem solved. Standard GM wires are not able to withstand the very high temperatures. You can get them from racing supply websites.

Michael Dion | Cedar Park, Texas

White letter A on teal backgroundThanks for writing, Michael, and for sharing your experience. Ignition problems can mimic fuel-supply problems, and vice versa, and are often misdiagnosed. The GM big block V-8 engines from the era of your motorhome have a well-deserved reputation for burning plug cables and boots. The cause is heat radiated from the nearby exhaust manifolds. There have been a number fixes, including heat shields and special boots, insulated cable sleeves, etc. I recommend that all owners take the time to inspect these cables carefully; viewing them while the engine is running at night is a good way to do it.

Fuel Starvation – Comment

Red letter Q
This is in regard to the “Fuel Starvation” letter in the January issue. While your advice to Dan Knowlton was excellent, I had a different problem. Due to uneven airflow around the engine, spark plugs and wires to cylinders 6 and 8 (right rear) would fail before the others, causing symptoms similar to Dan’s. Please download the following and read page 7-4 (www.gmcmi.com/wp-content/uploads/2014/05/P30-Chassis-Manual.pdf). I did the modification suggested in Figure 7-5 and the changed plugs and wires. Problem solved. By the way, you will find that the P30 chassis are actually P37 chassis, and the VIN will reflect this. There are differences between the two, with the major one being how the front-end alignment is accomplished. The rest of that manual is very eye-opening.

Larry Turner | San Antonio, Texas

White letter A on teal backgroundHave a tech question?As noted in “Backfiring and Power Loss Cured” (previous), fuel and ignition problems can mimic each other’s symptoms. Therefore, anyone diagnosing such problems should be wary and consider all possibilities. An automotive ignition oscilloscope will reveal such misfiring. Thanks for writing, and for sending the URL of the chassis manual. I have an original paper copy of the GM manual, but additional copies are getting scarce and many P-chassis owners will appreciate having this.

Over the years many of us have gotten into the habit of calling the GM motorhome P chassis “P30” although if you look on page 3-2 you will find GM refers to the motorhome chassis as P32 (I don’t see any reference to P37 as you state). It’s a minor point and I like to call it the P chassis to differentiate from G chassis, which were widely used on Class C motorhomes of the same period.

Bathroom Odors – Tip

Red letter Q
Regarding the January “Bathroom Odors” letter, I really feel for the Itasca owner’s issue with the bathroom odors. We have a 2012 Winnebago Sightseer 33C that developed a very similar issue. We really enjoy this coach and one of the first things I did when we bought it in 2012 was to install a Sani-Con macerator. I had no odor issues until about three years ago, at which time periodic sewer odors were apparent in the bathroom. I removed every possible access panel, the main control panel in the hallway, the toilet (installed new seals), the panels in the storage bins, bought a remote reading borescope to look in every possible place, filled (from inside the coach) the gray- and black-water tanks with water, and fussed a whole lot. After about a year, I decided to replace the plumbing roof vent covers with the 360 Siphon plumbing vent covers (based on an article in MotorHome). While doing so I decided to flush the vent lines with a garden hose – guess what, the black tank vent pipe was plugged. A sewer snake solved that problem and I added a T-fitting behind the hallway control panel for easier access should this occur again. As an experiment to see if the macerator was contributing to the problem, I stripped it out of the coach and have used the coach for more than a year without any odors (except maybe on rough roads that empty the traps). My current thought is that either when the coach was tilted enough that the vent was under “water” or that sufficient solids splashed upon it, the discharge flow rate using the macerator was insufficient to clear the vent line. Using a standard 4-inch gravity drain sure empties the tank faster, and you can hear the vent sucking air as the tank empties. Perhaps the Itasca owner has the same issue.

Lynn Eberhardt | Meridian, Idaho

White letter A on teal backgroundThanks for sharing your experiences. You sure went through a lot to solve this. Based on many owner reports, I find that tank vent problems are responsible for a high percentage of stubborn odor problems. I recommend that readers check these early on in any troubleshooting session.


Ken FreundRV DIYRV TechRV Tech Savvy

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