I took the car to a specialty driveshaft shop, and everything was OK with the driveshaft and the universal joints. The upper ball joints, the lower control arms, the inner and outer tie-rod ends, the strut rod bushings, the centerlink, the endlinks, the idler arm, the control valve, the slave cylinder, the front wheel bearings, and the shock absorbers have all been replaced.
The car also had a frontend alignment and the wheels and tires were balanced twice, but the vibration still persists. Do you know what may be causing this problem?Luis J. LlopizSan Juan, Puerto Rico
You certainly have been thorough by replacing most items that could contribute to a vibration. The only items you have not tried are different wheels or tires. A bent or out-of-round wheel can be difficult to observe. A faulty tire is even more difficult to detect, especially if it's internally damaged, such as a slight ply separation-which is impossible to see. The only way to trace this problem is to substitute new good wheels and tires for those on your convertible. Make sure you substitute wheels in pairs, such as both fronts or both rears, to avoid vehicle operation with one odd wheel/tire combo.
Silicon And Oil SuckersI have two questions regarding my '66 GT hardtop and the use of silicon brake fluid and a valve cover clearance problem.
What are the pros/cons on using silicon-based brake fluid? I am tired of replacing brake system parts due to trapped moisture in the brake lines. I've been told that using a silicon-based fluid will eliminate this moisture, but I'm uncertain of the drawbacks. Do you recommend using it?
Secondly, I have rebuilt my 289 4V to stock specifications with the exception of adding roller rockers. Since the rebuild, I have encountered two problems. First, stock valve covers do not provide enough clearance for the roller rockers. I switched to bigger valve covers, but they barely provide enough clearance. What do you think of using valve cover spacers? Are they still available? If so, where?
My second problem is related to the first. Since I am using valve covers with marginal clearance, it appears that the PCV valve is too close to the roller rockers and is sucking oil within the roller assembly and burning it during combustion. Because of the new valve cover, I do not have a breather hose on the left valve cover. Is this making the side with the PCV valve act similar to a straw? Any suggestions on how to cure this problem?Richard HudesSpringboro, OH
Silicon brake fluid seems to create controversy-some folks use it and some don't.
Basically, silicon fluid is incompatible with conventional brake fluid. They don't mix and remain separated when installed in a vehicle. If silicon fluid is added to an existing system filled with conventional fluid, it is impossible to flush out all of the conventional fluid by simply bleeding the brakes. Small traces of the original fluid will remain, where it sits like water spots, and will rot out steel lines or cause a spongy brake pedal, because it compresses differently from the silicon-based fluid.
The advantage to silicon fluid is that it does not absorb water and will eliminate damaged parts from moisture. The key is to completely disassemble or rebuild the hydraulic system to remove any conventional fluid before the silicon fluid is added. I've used silicon fluid in my collectible vehicles that sit for long periods, and the fluid eliminated any moisture-related problems.
The drawback of silicon fluid is that it cannot stand up to adverse brake situations that create lots of heat, such as racing or towing. Conventional brake fluid must be used, and frequent brake bleeding and flushing must be performed in order to remove boiled and moisture-laden fluid.