Driving Q&A: Pickup’s floor gets soaked when it rains

Question: I own a 1997 Dodge 3500 pickup I bought used about 10 years ago, and this problem came with the truck.

MCT / Times Colonist
December 13, 2012

Paul Brand, Minneapolis Star Tribune

Question: I own a 1997 Dodge 3500 pickup I bought used about 10 years ago, and this problem came with the truck. When it rains, water gets inside. It accumulates in the carpet in front of the front seats. In the past, I have had the windshield replaced and sealed and also sealed the roof-mounted amber lights — to no avail. A while back I took an awl and punched some holes in the floor on each side so the water will drain out. Although I’ve tried to dry the carpet, the bare metal under the dash is starting to rust and I’m fearful some of the electrical components will corrode. If I cover the cab from the rear of the doors to the middle of the hood, the water does not come in. What are the different possibilities I should investigate?

B.R.

Answer: If it’s not the windshield, the most common source of water collecting on the front floors is a plugged drain for the HVAC evaporator housing. Rainwater enters from the fresh air vents at the base of the windshield and should drain out at the firewall behind the right front wheel. Punching holes in the steel floor probably wasn’t a good idea because it created openings in the painted surface allowing that evil rust to start. As far as drying out carpets, the biggest issue is the carpet padding, which can’t be dried out and should be replaced.

Check for a blockage in the condensate drain tube, which allows water to drain from the evaporator housing. Access is typically from underneath the vehicle at the firewall, so take all necessary safety precautions and use a flexible piece of small-diameter wire or cable to gently probe and clear the drain tube.

Q: My 1999 Porsche Boxster was in storage for over one month and now the battery is dead. To open the front hood to access the battery, local dealers suggested jumping the C3 fuse in the fuse box with a spare battery. I connected the positive to both terminals on the fuse and the negative to the door frame as suggested — but no luck. The dash lights came up faintly once the fuse was jumped but the hood release did not work.

P.J.

A: I looked up Porsche’s emergency unlocking instructions in my Alldata database and find that you were on the right track by connecting battery voltage to both terminals of the C3 fuse. But there’s one more step in the instructions. With the driver door open and the jumper connected, use the key to lock and unlock the door. Once this is done, the hood release should work.

Q: We have a 2004 Chrysler 300M that has an intermittent problem with the background lights on the instrument panel. Sometimes the background lights for the speedometer and tachometer gauge will not come on in any position of the light switch. The background lights for the gas gauge, radiator temperature and clock always work. Of course, the dealership says it can’t fix the problem unless the lights are not working when the car is there. What can I do?

P.C.

A: Ask the dealer to check service bulletin #08-022-03, which identifies intermittent outages or changes in dash illumination. It suggests, rather than replacing the headlight switch, that you access the switch harness and unplug and plug it in three times to clean the contacts, then apply dielectric grease to the terminals.

Note: Regarding the loss of power steering on a 2003 Suburban, thanks to Rick Brandt for this tip: “I have experienced these power steering ‘;come and go’ problems before on high-mileage GM vehicles. I have found a simple cleaning of the reluctor rings on the variable effort steering switch (VES) can solve the problem. The switch is on the steering shaft, either just inside the firewall or outside.”

Q: If the timing belt breaks in an interference engine, it will self-destruct. What advantage is gained by this design that outweighs the risk of engine damage if or when the belt fails?

R.F.

A: This is an important topic because many engines can incur significant internal damage should an aging timing belt break. Automotive and light truck engines use either a chain, belt or, in rare cases, gears to synchronize the camshafts and crankshaft. A camshaft operates an engine’s valves, and the crankshaft transfers the up-and-down motion of the pistons and rods to the transmission, and ultimately to the wheels.

Belt-drive systems have been popular on overhead-cam engines because they’re inexpensive, quiet and lightweight. Chain-drive systems are making a comeback on many newer engines because they’re sturdier and longer-lasting than timing belts. An engine can have one, two or four camshafts.

Many engines are designed such that the valves can collide with each other or the top of the piston, should the belt or chain fail, and the cams and crankshaft lose synchronization. This is known as an interference engine, and is a compromise of performance and failure likelihood and consequences.

Engine performance is all about breathing and a higher-than-typical compression ratio. Superior breathing requires large valves that open deep into the combustion chamber and high compression means a smaller-than-typical combustion chamber. This means the valves may need to extend into the area swept by the piston, and that’s where interference may occur. The worst case I’ve heard was around $6,000 in damage to an engine due to a failed timing belt; in most cases it may be around half that or less.

Timing belts are highly durable, and failures are rare. Most automakers recommend belt renewal at around 145,000 to 195,000 kilometres to play it safe. Belt replacement can be a big job, with a cost between $500 to $1,000, as the water pump, belt tensioners and other parts are usually recommended to be replaced at the same time. This is prudent, as anything that’s driven by or contributes to belt tension could cause a failure that breaks or derails the belt. Obviously, a service item such as this should be a consideration when purchasing a used car.