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Jim Grant's Tech Tips
‘94 Isuzu Rodeo, Slipping Clutch
Q: So far I have installed the following in my '94 Isuzu Rodeo 3.2 with a
manual transmission. A new clutch, clutch master cylinder, clutch
slave cylinder, clutch and pressure plate. But, after all of this
work the clutch continues to slip after driving the vehicle for 15
minutes. This has been a persistent problem. I overheard a dealer
mechanic say that it was a problem of design, the fluid line was too
near an exhaust pipe. Not even the dealer has been able to address
this problem.
- Daniel
A:
For a clutch to start slipping after the vehicle has been driven a
short time and all of the components are known to be good then it is
likely that your problem is an adjustment issue. The hydraulic clutch
in your vehicle uses brake fluid. Brake fluid, as it is heated,
expands. Because brake fluid expands, a provision is designed into
the system to allow for the expanding fluid. If this provision were
not in place, as the fluid heats and expands, the clutch would start
to release. The expanding fluid would be applying pressure to the
hydraulic clutch as if you were starting to step on the clutch pedal.
On the back of the clutch master cylinder, there is a push rod that
connects to the clutch pedal. This push rod is adjustable. If the
push rod is incorrectly adjusted, it will cause the piston in the
clutch master cylinder to block the compensation port in the clutch
master. If this port is blocked the brake fluid cannot go back into
the reservoir as the fluid expands. The pressure in the hydraulic
clutch system will increase. This increase in pressure has to go
somewhere. That somewhere is the clutch slave cylinder. The build-up
of pressure is the same as if you were holding your foot on the clutch
just a bit. So, check that push rod's adjustment, you'll likely find
that there is no free movement and the push rod is in fact pushing a
bit on the clutch master cylinder piston. As a heads-up, I have seen
people adjust this push rod in an effort to improve the clutch pedal.
The reason for this incorrect adjustment was to compensate for a poor
clutch pedal. The reason the clutch pedal was poor is due to the
clutch not being bled correctly. There are two bleed points on most
Isuzu systems. One is at the clutch slave, but there is one
in-between at the damper for the system. If the damper is not bled
correctly, the clutch pedal quality will be poor. A few inspections
and a little adjusting should take the slip out of your clutch.
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