1989 Isuzu Trooper Clutch Hydraulic Problem

Hello All:

I have a 1989 Isuzu Trooper (don’t smirk, it’s been a good car). Two years ago I replaced the transmission and clutch. Since then, it has acted poorly in hot weather, failing to engage the clutch so that I grind the gears or worse not being able to shift. Willy, my mechanic at Trans-King has checked it all out and replaced the clutch (for free) and it still acts up in hot weather. When he replaced the clutch, he had to bypass the failed servos (none being available for replacement) that apparently helped to boost the pressure in the thin clutch lines.

The symptoms: It starts out fine on a hot day, but once you park and start up again, there it is, grinding and failing to shift gears. Bleeding the clutch seems to correct the problem, but Willy can’t find a leak anywhere in the system. He’s offered to bleed the clutch for free for the life of the Trooper and I know how to do it by myself using a cut-off broomstick to maintain pressure on the clutch pedal, but I primarily use this as my desert vehicle. So, I would appreciate you offering a solution to prevent me from having to bleed the clutch in the middle of the Mojave Desert at high noon. The last time I talked with Willy, he suggested trying to insulate the clutch from the heat of the desert road. Before doing that or going out and buying a big slurp water gun, I thought I’d contact you

Thanks for your consideration of this persisting problem.

Mick Bondello,

presently cool in Coastal California

You may have a clutch master cylinder that’s being effected by engine heat.

When this happens, the clutch master cylinder gets hot enough where the bore of the master cylinder expands. This prevents the cup seal in the master cylinder from completely sealing in the bore. This then allows the hydraulic fluid to by-pass the cup seal where no hydraulic pressure can be produced to operate the slave cylinder. This then is like trying to shift the transmission without stepping on the clutch pedal and the gears grind.

One way to check for this is, carry a bottle of water in the vehicle. The next time the clutch doesn’t function, pour that water over the clutch master cylinder. If hydraulic pressure is restored, it pretty much confirms that the master cylinder is being effected by the engine heat.


Thanks Tester, I’ll give this a try. I’ll also print your reply and show it to Willy.