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  • TDC - Technical Questions & Answers - March 2005

TDC - Technical Questions & Answers - March 2005

Bruce Caldwell
Mar 1, 2005
Photographers: Bruce Caldwell
Photo 2/3   |   technical Questions And Answers March 2005 truck Cartoon
Q: I have a '97 GMC Suburban two-wheel-drive barn-door model with the 5.7L V-8 and automatic transmission. I've lowered the truck with spindles, springs, and hangers. I'm running 18-inch rims and I've done some paint and body mods, but I've left the engine stock except for a K&N filter. I use the truck for daily driving and weekend boating.
My problem is a ticking noise that reminds me of a cartoon time bomb about to explode. I know it's not a bomb, but I'm still concerned. The noise is definitely coming from the engine compartment. I've had passengers comment on the noise, so it's not just me. I thought it might be a loud or defective fuel pump, but the noise seems loudest on the right side of the engine. I'm also pretty sure it isn't a problem with fuel injectors. I've had cars with noisy injectors, but this ticking doesn't sound like that.
The noise seems loudest in the morning when I first start the truck. The colder it is, the more noticeable the noise is. My Suburban runs fine, but now that I've become aware of the ticking, it's starting to drive me crazy. Have you heard of similar problems? Is there anything reasonable that I can do to cure the problem?
I have another less annoying problem. The rear barn doors are getting harder and harder to open. They seem much stiffer than before. I've had some short-term success with spraying WD-40 on the hinges, but no permanent improvement. The door gaps seem fine and the doors don't appear to sag. Is there an easy way to fix this problem? Thanks for your time and help.
Nolan Kerrigan, Cocoa Beach, Florida
A: Noises without a definitive source can be difficult to diagnose. Given your location, description, and the fact that the ticking is most noticeable when the truck is cold leads one to suspect the evaporative canister purge solenoid. The solenoid is mounted on the right side of the intake manifold, close to the throttle body. The action of the valve plunger hitting the port seat is what makes the ticking sound. Noise from the purge solenoid will be most noticeable when the engine is cold.
The solution is to get a new, improved solenoid (PN 1997277) that was designed to eliminate the ticking. Depending on the mileage on your truck, there is a chance that the solenoid replacement may be covered by your warranty. It's worth checking into.
This ticking noise problem with the evaporative canister purge solenoid is common in a great number of '97 and '98 GM light trucks. The vehicles affected include: Chevy C/K pickups and Suburbans, S-10 and Sonoma pickups, Blazers and Jimmys, and Astro minivans. Engines that may have this problem include: 4.3L V-6, 5.0L V-8, 5.7L V-8, and 7.4L big-block V-8. RPO codes are L35, LF6, L30, L31, and L29.
Your obstinate rear doors are a problem shared by many '92-'97 Suburbans with barn doors. People who live near saltwater or other corrosive elements tend to have the most problems. The hinges corrode, which makes them stiff. Lubrication will help, but the best solution is new hinge pins and bushings. Replacement is simple and you should be able to do it yourself.
Alternating Slippery Conditions
Q: The alternator on my '93 Ford Ranger pickup seems to vary in its effectiveness. Most of the time it charges fine, but other times, it doesn't seem to charge as it should. The engine is the 4.0L V-6 and the transmission is the automatic. The truck has two-wheel drive and a Traction-Lok differential.
The alternator charges fine on nice, sunny days, but when it's rainy or after we've had a lot of snow and it's melting, the alternator performs poorly. I had the alternator checked at my local parts store and the guys there said it was up to specs.
I checked the drivebelt tension and the belt condition. Both things seemed fine. Is there a reason the alternator would intermittently underperform? Could I have some type of short that doesn't show up when the alternator is on the parts store's test bench? The closest I can come to pinpointing the problem is that wet weather seems to be a factor. Does that suggest anything to you? I don't want to buy an unnecessary alternator, but I also don't want my battery to fail.
Another problem I have is noise and vibration in the rearend. This problem tends to happen after I've done quite a lot of freeway driving and then I go somewhere on surface roads with lots of curves or turns. The chattering-type noise is most noticeable when I make a sharp turn at relatively low speeds. If I make a U-turn, the noise is worst of all. Is this a sign that something's going out in the rearend? Is there something I can do besides not turn corners? Thank you.
Marc Richmond, Green Bay, Wisconsin
A: Your guess that the alternator problem is weather-related is probably correct. Other Ranger owners have experienced similar problems. The alternator is OK, but there can be too much moisture on the alternator drivebelt. Areas with lots of rain, snow, or potholes can make the problem worse. Melting slushy snow is probably the worst condition for this problem. All that splashing moisture is getting on the drivebelt. When the 'belt gets too wet, it can slip and cause the observed difference in alternator performance.
According to Ford's service bulletin TSB 94-18-8, the solution is a splash shield to better protect the drivebelt. Ask your Ford parts department for splash shield F37Z-16103A.
You said you checked the 'belt tension. That's something everyone should include in his or her preventive maintenance. The basic rule is that there should be about a 1/2 inch of deflection at the center point of the span between two pulleys. Individual trucks may have a specific deflection recommendation, but the 1/2-inch rule is a good starting point. There should be some deflection, because a too-tight 'belt can also be bad for the alternator.
Your rearend noise and vibration symptoms sound like Traction-Lok problems. Two possible problems are a lack of friction modifier in the lube or clutch packs that have been overshimmed. You can drain and change the rearend lube yourself. Be sure you get the right lube, or you'll be right back to the same old problem. If the new lube doesn't solve the problem, you'll need to have the clutch pack checked by a specialist. Other owners of '93 to '96 Rangers with the Traction-Lok differential have reported similar problems.
Photo 3/3   |   technical Questions And Answers March 2005 rabbit Cartoon
Q: I think one or both of the exhaust manifolds on my '96 Chevy Silverado are damaged. The truck has the 5.7L V-8 and the automatic transmission. It has more than 140,000 miles on it. I've had bad exhaust manifolds and headers before, so I'm pretty sure this is the problem. It definitely sounds like a bad manifold. I'm quite certain that the right manifold is cracked, but I'm not sure about the left one.
I tow a 24-foot travel trailer in the summer, so the truck gets some pretty hard use, especially when crossing mountain passes. Can hard use contribute to cracked exhaust manifolds? Would headers be a better idea? If I find that the exhaust manifold is cracked and I have it welded, will it just crack again in the same place? I'd appreciate your advice.
Barry Noonan, Butte, Montana
A: Cracked right-side exhaust manifolds have been a problem for '94-'96 GM pickups with the 5.7L V-8. Extreme-duty use such as towing a heavy trailer long distances in hot weather will exacerbate the problem. The manifolds get very hot and then cool off. The technical term for this condition is thermal cycling stress. These extremes of temperature can lead to stress lines, which eventually become full-fledged cracks. Sustained high engine speeds can also contribute to exhaust manifold cracking.
General Motors has a couple revised exhaust manifolds to fix the problem. Engines that were built in 1994 and early 1995 require right-hand exhaust manifold PN 12524289. A way to identify the earlier exhaust manifolds is that they have separate AIR tubes screwed into each individual exhaust runner. Later engines such as yours use exhaust manifold PN 12556731. These revised manifolds use a single AIR port that's located at the front of the manifold.
You could have the crack (or cracks) welded. The quality and longevity of the repair have a lot to do with the skill of the welder. We'd skip the risk and just get a new, revised manifold. Headers would be a fine alternative and would give you extra power for trailer towing.
Oil Rich
Q: I have a '90 Ford XL longbed pickup with the 5.8L 351ci engine and four-speed automatic. The mileage is fast approaching 200,000, but no major work has ever been done to it. It runs fine, but does tend to use oil. This truck has become sort of the family chore truck. Everyone borrows it whenever they need to haul something. I'm fine with that, as long as they bring it back full of gas and watch the oil consumption.
My reason for writing you involves the oil consumption. I tell everyone who borrows the truck to keep close tabs on the oil level. A young relative used the truck to move 600 miles away. He had the truck for almost a month. When it was returned, I checked the oil level and it was over-full. I changed the oil and my best guess is that it was 1 to 1-1/2 quarts over-full. I don't know how long he ran the truck this way.
My question is: Can over-filling the oil harm an engine? The truck runs like it did before, so there isn't any obvious damage. I've only admonished borrowers to not let the oil level get too low. Should I make a big deal about not over-filling it? What do you think?
Jim Harwick, via e-mail
A: If the engine was only 1 quart over and it still runs fine, it probably is fine. You didn't mention if the oil looked different when you checked the dipstick. If the oil was foamy or frothy, it could be aerated. This can cause oil pressure to drop, which can cause damage.
If the level of oil in the crankcase gets too high, it can reach the crankshaft. The action of the crankshaft will whip the oil, leading to foam and lower oil pressure. Also, if oil levels are too high, it can start to find its way out of the block, through gaskets, seals, or PCV components.
At The Hop
Q: I did a 4/5 drop on my '99 Chevy S-10 shortbed regular-cab pickup. I accomplished the drop with a combination of spindles, springs, and lowering blocks. I added 17-inch Billet Specialties wheels and 40-series BFG rubber. The truck looks great, but now it has rear-wheel hop. Is this normal, and what can I do to eliminate it? Thanks for your help.
John McDonald, Phoenix
A: When you lower a truck, you change the rearend pinion angle. You need to measure and check the pinion angle. A protractor with a movable indicator will allow you to make comparison readings. Make sure the truck is on a level surface when you take your measurements.
Your pinion angle should be 1 to 1-1/2 degrees of downward angle relative to the driveshaft. If this isn't the case, you'll need some leaf-spring mounting shims to achieve the desired angle. Typical shim kits come with 1-, 2-, and 3-degree-angle shims.
Spring wrap-up is another component of wheel hop. Stiffer rear leaf springs will help control hop. A custom spring facility may be able to help you. The right shock absorbers such as adjustable ones can also help. Individually adjustable shocks will let you preload one side of the suspension.
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