Momentary loss of drive

[iain.hamlton]

This has me baffled so all suggestions welcome.

The engine, gearbox and clutch operate well normally. Except on on three occasions now - so not every time - , when I accerate hard in third there is a momentary loss of drive, as if the clutch is dipped. My foot is clear of the clutch. This happens when the engine reaches about 4500 rpm, so it suddenly revs higher. Is this a the first sign of a worn clutch? In my experience worn clutches first show signs as you engage top even at low revs - but this seems different.

thanks and best regards, iain

[Hamish Coutts]

Ian,

To me the first sign of a worn clutch is slipping - where it sounds like you still have your foot partially on the clutch. The engine revs rise out of proportion to the gear selected. They don't rise suddenly, though.

That said, it does sound like a clutch problem as that is the only component in the drive train that can disconnect/connect the engine from the rest of the gubbins. Looks like you will need to have a look at the clutch .
That's what I would be thinking of doing if I was in your position.

Before you do that is there anything suspicious looking about the slave cylinder or its linkage to the clutch. I'm thinking about small stones or other debris jammed in somewhere? Or other damage such as impact with a hard object? It is pretty exposed down there.

Hamish.

[alaric]

Hi.

To clarify, it sounds like your drive goes and then comes back again from the way that you've written it in the post. If this is the case, then when the drive comes back, if there's not a loud clunk i.e. it's not violent, I would vote for the clutch as the point at which the drive train is broken. The fact that it's in third gear each time at the same revs is a bit weird though isn't it? Maybe something in the clutch actuation is rattling around and that it's more likely to cause a de-clutch at that speed due to a resonance.

I'd be tempted to get the whole assembly out and replace worn bits including the clutch - I'm with Hamish.

These cars certainly throw up some interesting problems...

Sean.

[1964 S1]

...third gear, maximum torque with near maximum wind resistance equals slipping clutch? Do you see any liquids dripping from between the bell housing and engine block?

[denicholls2]

Every car I've ever driven with a worn clutch (a surprising number, actually) had exactly these symptoms. You are driving in a band where the engine has the greatest potential to overrun the drivetrain -- resistance to the load is highest as is torque.

You probably have a long way to go, but you can confirm the problem by driving at a steady speed when you're near the torque peak of the engine and nailing the throttle. I'm confident you'll see (and feel) the engine surge while the car lags.

While given the weight of an Elan I'm confident you can, running for a long distance (thousands of miles) in this condition will take a toll on the flywheel.

[iain.hamlton]

I have tried all the usual things that indicate a worn clutch... Max torque in top (full throttle 4K -5k): no slip. then touch the clutch pedal. It doesnt slip until the pedal has moved quite a bit; rough gear changes - grabs immediately. The clutch itself seems fine, and symptom hasnt been back. I am baffled. I think I'll bleed the clutch hydraulics in case there is some water in there boiling where the pipe is close to the exhaust manifold.

I am doing the Anglesey track day next weekend, so if the car gets from Fleet to Anglesey plays all day then home without problem I shall not worry. If the problem is going to develop it will....

[1964 S1]

Can water boiling in the clutch line make a clutch slip? I'd think just bubbles in the resevoir. Pressure on the slave cylinder? Was the car fully warmed when it happened? It could be oil on the clutch plate surface.

[M100]

Can water boiling in the clutch line make a clutch slip? I'd think just bubbles in the resevoir. Pressure on the slave cylinder? Was the car fully warmed when it happened? It could be oil on the clutch plate surface.

Fluid boiling or the pipe expanding can make the clutch not release (same problem on the Elan and Elise 30 years apart!) I doubt it could make the clutch actuate.

I'd look and see if the *master cylinder* push rod is clear of the piston when fully released and check the slave cylinder pushrod clearance.

[rgh0]

In most Elans the clutch slave cylinder can move in the mounting a few millimetres backwards and forwards as the circlip location is not perfect. It is possible as you change up for the cylinder to jam in the backward position. This removes the clearance of the push rod and release bearing mechanism and could lead to an intermittent clutch slipping problem.

regards
Rohan