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Engine revs, no power, only when hot

I have a 1995 Honda del Sol manual transmission.
I only have this problem when it is hot outside and I’ve been driving at freeway speeds. I’ll press the accelerator and the engine revs but there is no power going to the wheels. The tachometer revs up but my mph keep dropping. If i push the accelerator very slowly, eventually the RPMs will drop down and power to the wheels will be regained. This ONLY happens when the weather is hot, above 80 and I’ve been driving the car for probably a half hour or more.
Anyone have any idea what it could be?

My first guess would be a slipping clutch.

It sounds to me like you need a new clutch. Next time you drive the car, try to shift from 1st to 2nd and then to 5th while accelerating hard. I’ll bet you can duplicate the problem.

That’s what it seems like when it’s hot but it never slips like that when it’s not hot outside. I’ll definitely try the shifting test.
I’ve had a car that needed a new clutch before it didn’t just slip occasionally, it was all the time. If that is it, why does it only happen when it’s hot?

My guess is an oil leak from the transmission. After a half hour of driving, you get enough oil on the clutch to cause it to slip, though it seems odd that it does not continue to slip when you start the car cool. If I am correct, eventually it will slip all the time, or the oil level in the transmission will get low enough that it won’t leak any more. If you drive that way, your bearings will fail in the transmission.

And it only happens when it’s hot out. I could drive it today, its only 70, and it wouldn’t happen. It has to be over 80 and even then, it doesn’t always happen.

I am going to go with water in the clutch fluid, boils, causes air bubbles, clutch slips. Flush the clutch hydraulic system with fresh fluid and see what happens. With that said the clutch itself is probably damaged at this point so it may not be long for this world.

Next time your’e cruising on the freeway in 5th gear and don’t have any traffic immediately behind you momentarily press the clutch pedal halfway down and quickly release it. If the clutch slips at this point, it’s toast.

Tried the 5th gear thing, clutch didn’t slip at all. Actually haven’t had the problem since it’s been winter (well in Los Angeles “winter”).
One other mention, there is a leak of clutch/brake fluid coming from the clutch pedal. Every so often I have to fill the reservoir because it’s empty. Could this have something to do with it?

You need a new clutch.

If the clutch master cylinder is leaking to the point where it’s empty, at some point not enough hydraulic pressure was developed to fully disengage the clutch. And this will burn a clutch up in short order.

Eventually the clutch will slip so bad that vehicle won’t move. So best to get the clutch assembly replaced before that happens. Along with a new clutch master/slave cylinder.

Tester

When the clutch is operating correctly, take note of where the engagement point is located i.e. how far the pedal has to come off the floor to where the clutch is really pulling. As the engine warms up see if that engagement point rises i.e. come closer to the pedal full up position. Also pay attention to the free travel of the pedal on the down stroke before it becomes stiffer and see if the free travel deminishes.

I am wondering if the master cylinder is trapping fluid and not allowing expanding fluid to escape back into the reservoir. It could be a problem with the pedal up stop; the master cylinder push rod length adjustment; or the master cylinder itself.

Hope this helps.

It could also be that the fluid in the clutch hydraulics has degraded enough to where heat is causing it to expand although not boil. That could lead to partial disengagement of the clutch and slippage on a tight clutch and while rare is a possibility anyway.

Given the age of the car and slippage problems it could be that a new clutch kit may be needed even if a potential fluid issue is resolved.

Veronykah, your clutch is slipping It’s that simple.

The engine is supposed to be directly connected to the rear wheels through gears and hardware. Anytime the power at the rear wheels fails to respond to increased RPPMs of the engine, the two MUST be becoming disconnected. The single thing in the entire power train that has the ability to allow the engine to become disconnected and reconnected to the rear wheels is the clutch.

If you don’t get your cluch assembly changed, this will gradually get worse until one day you’ll punch the gas on your Del Sol to merge in front of an 80,000 pound big rig and you’ll be unable to do so. Best case, it’ll scare the bejesus out of you. Worse case, your Del Sol and you will be a pancake. Yes, this IS a safety issue.

I mean no disrespect, but you need to get your clutch assembly changed. The good news is that it’s Honda Civic parts, so the cost should be affordable.

I’m going against the grain again. You may need a new clutch, but I think the root cause of your current problem is the slave cylinder, but it could also be the master cylinder but I think more likely the slave cylinder.

One of those is leaking and the cause of the leak is also the cause of your problem. If the master cylinder was leaking, you would have noticed that the floor on the drivers side of the car is damp from the brake fluid, since you didn’t mention this, I am going with the slave cylinder.

Under certain conditions, heat being one of them, fluid is seeping past the seal and getting trapped in such a manner that it keeps the piston from completely returning to its rest position. Eventually it seeps out of the area it is trapped in, but I think that once you fix the leak, you will fix the problem. Then a week or two later it will return, but this time it won’t be temperature dependent, because the rest of the clutch is toast from the premature wear that this is causing.

Hydraulic pressure can only be the cause if the master cylinder piston is being held beyond the reservoir port.

That is true if it is hydraulic pressure hold the clutch partially disconnected. This is another reason that I think it is the slave cylinder. What ever is causing the slave cylinder piston to not fully return is also the cause of the leak. It could be that the piston is getting slightly cocked in the bore due to a bad seal and is hanging up. It could be something else.

Whatever the reason, the odds are that the two problems are related and if you replace the leaking part, you will fix the slipping issue, for a little while anyway. The op may not realize that even when the clutch does not appear to be slipping, it might be slipping, just not enough to be noticed and all this slippage is causing excessive wear and tear on the whole assembly.