Defective seals often cause leak in steering rack

Hey there, time traveller!
This article was published 13/06/2003 (8309 days ago), so information in it may no longer be current.

QUESTION — What could be causing our steering rack to leak and have to be replaced twice in 48,280 kilometres?

We have a 98 Grand Caravan that was modified new for wheelchair access, by lowering the floor. The modified vehicle is a few hundred pounds heavier than the vehicle before modification. The Chrysler dealer suggests that the steering rack wears out because the van is raised at the rear to improve clearance under the lowered floor. The van was involved in a minor collision in 2001 that resulted in a cracked front bumper. Thanks in advance for your consideration.

ANSWER — Two problems typically occur with steering racks. First, there is an internal seal leak on the piston that allows fluid to leak from one side of the piston to the other. This causes harder steering because the power assist is being bypassed. The second problem is an external seal on the steering rack that falls and allows oil to leak to the outside. Problems can also occur in the hydraulic control valve area of the steering rack, but these are rare. Regardless of the problem, the typical repair is to replace the steering rack with a rebuilt or remanufactured unit. Few shops actually disassemble steering racks for repair.

To help determine why the rack needed replacement a second time, we should look at why it failed the first time. The extra weight of the vehicle may place a slightly higher load on the rack, but this would occur only when the wheels are being turned with the vehicle stationary. Even this should not cause a real problem, as the van was designed for maximum passenger load and I doubt if you operate it this way most of the time. The raised rear end also should not cause a problem with the rack, although it would change steering angles slightly. I suspect the first failure may have been just bad luck, but the minor collision may have had something to do with it.

I often see vehicles that have been in collisions that had no obvious damage to the steering but were hit hard enough on a tire or wheel to damage something in the steering or suspension. Winter accident damage may not show problems until there are smoother roads and better traction in the spring.

The second failure could be related to the first. If the oil in the steering was contaminated with metal particles from the first failure, it should have been flushed before a new rack was installed. Check the power-steering oil and if it appears grey or has small metal flakes in it, then it needs changing. The second failure could also be caused by a steering-rack boot vent tube that was not securely in place, allowing dirt and moisture to get in. Unfortunately, this would be difficult to determine unless you saw it at the time the rack was replaced. Again, the second failure may have been just a case of bad luck.

QUESTION — My daughter owns a 1990 Z24 Cavalier with 3.1-litre engine and auto trans. The timing chain broke and the valves bent. We would like to know if there would be any problems with taking a 3.1-litre engine out of a 1992 Pontiac Sunbird with 3.1-litre engine and auto trans. Any information you could provide us would be greatly appreciated.

ANSWER — These two engines have a different option code number but appear to be mechanically basically the same. Unfortunately, shop manuals and interchange manuals don’t tell you all the exterior differences, so the best method is to visually look carefully at the two engines. There may be some minor differences in throttle cable brackets or accessory mounts, but these should be easy to swap.

The wiring harnesses for the two engines are slightly different. I would keep the original harness with the vehicle and swap any sensors that have different connectors. The location of the oil-pressure sender appears different too. There should be a plug in the block of the Sunbird engine that can be removed to install the Cavalier oil sender. You can remove and plug the Sunbird pressure sender if you wish, but it is not necessary.

Almost all engine swaps require small changes and sometimes major ones, such as swapping oil pans. Your swap appears to be relatively easy.

Jim Kerr is an experienced mechanic, instructor of automotive technology and freelance journalist. You can e-mail questions to Jim at the address below.

kerr.jim@sk.sympatico.ca