Q: I recently bought and am restoring a 1978 Cadillac Fleetwood Brougham. All was going well until I tried to repair the heater. No heat! The blower motor works fine, but will only send cold air out the floor vent no matter what setting I put it on. It has a new thermostat and great circulation to and from the radiator/heater hoses. Any ideas would be appreciated. I love reading your column every week in the News.
A: Numerous problems could cause the vehicle to have no heat. First, the most common is the hot water valve located under the hood. You can check this by feeling the heater hoses in and out of the heater core. Both hoses should be hot. If one is hot and the other is cold, you can suspect the valve or a blocked core. Next, and the most miserable of all, is the programmer assembly, which is located against the firewall under the glove box. This electronic device sets the temperature and where the air is delivered. They were a nightmare then, and I am sure they still are today. The best case would be a broken vacuum hose under the hood that feeds the HVAC system. The hose should come from a canister that looks very much like a quart can, which many years ago was used to get grapefruit juice at the grocery store. This canister should have an engine vacuum hose going in and a hose that feeds the HVAC system coming out. These cans would typically rot out and not send vacuum to the HVAC assembly. Best of luck restoring this classic beauty.
Q: I have a 1997 F-350 pickup with a 351 engine. I have replaced both exhaust manifolds four times, once on the driver’s side and three times on the passenger side, which cracked again. The converter is about a year old. A second problem is that I keep having power loss. The truck will run fine, then it’s almost like I lose a few cylinders. It could last a minute or 10 to 15 minutes, hot or cold. Lately it’s a lot worse when it’s wet out. I’ve checked for codes — none. I’ve replaced the MAF sensor on the firewall, cap, wires, plugs, rotor, fuel filter, TPS and coil. The truck has about 130,000 miles. It’s in good shape but has had a hard life. Any suggestions?
A: Everything you tell me leads to a lean mixture problem. A computer scan will show you have a lean condition when monitoring the long- and short-term fuel trim. The excess heat caused by the lean condition is the reason you are going through exhaust manifolds. A few things that could cause the lean condition are: restricted exhaust; low fuel pressure and volume; an erroneous reading by the oxygen sensor, which may be setting the fuel lean; a clogged fuel filter; a failing fuel pump; an in-tank fuel filter that is getting clogged; or even an old fuel filter that is reducing the fuel flow.
Car Care Tip: If you use a canned emergency tire inflator for an emergency flat, let the repair person know what you have done. It will help to prevent personal injury.
Larry Rubenstein is a master technician who owns a North Shore service station. His column appears every Saturday. Write to Larry at The Salem News, c/o Auto Scanner, 32 Dunham Road, Beverly, MA 01915, or send an email to email@example.com.