volvo 340 GL cvt high revving (HELP)

[lewy]

The connections A and B are different, connection B the kickdown vacuum is unrestricted this is because for kickdown you want a quick response of the gearbox to select a lower gear so you can overtake.
Connection A the “gear up” vacuum is different. In the factory the EMV’s got a restriction on the A side to allow around 400mBar through, this is to make sure the car doesn’t want to go from 1st to 5th gear instantly when taking off and allows a efficient and smooth gearchange (1st, 2nd, 3rd, 4th, 5th) when driving, as far as this automatic wonder is comparable to a manual car offcourse!

If you take a look at the EMV the 2 sides have different wire colors, at side where hose A is connected, there’s a grey and a green wire. Where hose B is connected, there is a brown and a yellow/green wire.

To check side A, run the engine in N, press your finger gently to the connection on the EMV; now raise the rpm’s to above 1800, this connection should now suck noticeably by your finger.
To check side B, run the engine in N and let it idle, switch on the low gear hold switch inside near the gear lever and you should hear it suck noticeably.

hi volvodspec,
i have noticed the little restrictor in the pipe to the rocker box cover, and when i put a vac gauge on the vac side of the EMV i get around 600mBAr, is this to much, both sides are sucking in their respective order, all the electrics are now working ok, the rubbers have been changed in the EMV, but stll revs to high.
i shall check the clutch gap this weekend coming, the belts and gap have been adjusted, perhaps i am to heavy footed!
lewy

[volvodspec]

600mBar, lucky basterd!!!
that "should" give you a very sweet driving as it will select a slightly higher gear (like the 5th where it would normally do 4th) when you drive steady at around 40mph

can you please PM me your emailadress, i will send you the translated diagnostics page with a few added bits of info for you to check out!
currently i suspect the fault to be the gearbox and NOT the clutch/airgap.

if you have problems with a too large airgap you only notice this on takeoff (car should takeoff slightly above idle!). as the centrifugal force increases when you rev it clutchslip at higher speeds is very rare unless there is oil/fluid on the clutchplate.

[lewy]

no the car does not rev like clutch slip, it just over revs whilst normal driving, on take of it starts to pull around 2000revs, i am stating to suspect a switch again!
lewy

[lewy]

600mBar, lucky basterd!!!
that "should" give you a very sweet driving as it will select a slightly higher gear (like the 5th where it would normally do 4th) when you drive steady at around 40mph

can you please PM me your emailadress, i will send you the translated diagnostics page with a few added bits of info for you to check out!
currently i suspect the fault to be the gearbox and NOT the clutch/airgap.

if you have problems with a too large airgap you only notice this on takeoff (car should takeoff slightly above idle!). as the centrifugal force increases when you rev it clutchslip at higher speeds is very rare unless there is oil/fluid on the clutchplate.

pm sent.
lewy

[lewy]

Have you checked the clutch plate gap? If this is to far away from the drive plate the revs will increase and also give poor top end power while driving. If gap is to wide you will have to remove a shim/s to get the correct gap.

would this give me clutch slip like in a normal clutch system?

[lewy]

600mBar, lucky basterd!!!
that "should" give you a very sweet driving as it will select a slightly higher gear (like the 5th where it would normally do 4th) when you drive steady at around 40mph

can you please PM me your emailadress, i will send you the translated diagnostics page with a few added bits of info for you to check out!
currently i suspect the fault to be the gearbox and NOT the clutch/airgap.

if you have problems with a too large airgap you only notice this on takeoff (car should takeoff slightly above idle!). as the centrifugal force increases when you rev it clutchslip at higher speeds is very rare unless there is oil/fluid on the clutchplate.

just done vacuum again, the overdrive side is 300mbar from the small pipe side of the eMV, and 600mbar on the big pipe side,
take the vacuum reading straight from the big pipe from carb and manifold and i get 600mbar, is there a problem with the EMV?
its had a new overhaul kit fitted, and all the electrics and pipes are now good!!!
so its got to be low vac reading giving me high revs!!!!!!

lewy

lewy.

[pettaw]

95% certain its the clutch adjustment mate. All the CVT's I've come across have had completely knackered clutches, because they weren't looked after by the previous owners or owners garages. Clutch adjustment needs to be checked once a year or every 10,000 miles and then adjusted if necessary. Trouble is that they wear very gradually and the owners don't notice the gradual 'higher revviness" of the car until someone who knows how these cars work drives them. Trouble is that most garages don't understand these cars or their transmission systems at all.

Its a particular problem when it comes to the MOT test, to clear the exhaust system and stabilize the oil temperature the tester normally holds the engine at approx 2500-3000 rpm for approx 20-30 seconds, although I've witnessed many ham fisted mechanics revving the nuts off the cars....quite why I don't know. And of course with most auto transmissions, its quite OK to do this in Park OR Neutral, but NOT in our CVTs! If you rev the car up hard in Park, the clutch will engage and burn up against the locked transmission. Therefore, never ever rev the car above approx 2,000 RPM in Park, in fact, that's only really a safety net and you shouldn't really be running the engine in Park at all. Much safer to only ever run the car in Neutral, and you're quite within your rights to 'remind' any MOT tester that the car should remain in Neutral for the tests and not Park.

Quick test requiring no dirty work at all to test where the clutch engages. Put the car in drive as though you're going to pull away with the car idling. Raise the revs very slowly and note the point at which the clutch first engages. If you can, get someone to look under the car at see when the propshaft first begins to turn. I'm talking about the first biting point, not where the car starts to move, just where it takes up the slack. If all is good it should be at approximately 1100 RPM. If you have no rev counter, its only very slightly above idling speed. If its any higher than that, say 1500 rpm, then your clutch needs adjusting. If its any higher than that, your clutch needs replacing completely. When we did one we found it was completely worn through to the bare metal carcass, luckily it was on the pressure plate side, because if it had been on the flywheel side, the flywheel would have needed resurfacing! This was on a car that had done 70,000 miles I think. The other one was on a car that had done less than 10,000 miles and the clutch was already worn down to the rivets.

Moral of the story, never rev the engine in park, and keep an eye on the clutch adjustment. It needs regular attention otherwise you will be replacing the clutch frequently!

Hope that helps.

[morgan105]

[quote="lewy"][quote="morgan105"]Have you checked the clutch plate gap? If this is to far away from the drive plate the revs will increase and also give poor top end power while driving. If gap is to wide you will have to remove a shim/s to get the correct gap.[/quote]

would this give me clutch slip like in a normal clutch system?[/quote]


Sorry for the late reply only just picked up on this again.

It may only be noticable from a standing start on a hill or a heavy foot from standstill. If you don't have a heavy foot the clutch will engage as normal as it will take up the drive slower. The clutch on the CVT works on rollers and is not engaged all the time like a ordinary clutch, it will only engage with revs being up and allowing the rollers to move out which then pushes the plate to the flywheel. The rollers can move out quite a bit, more then the clutch wears, so if the clutch is not adjusted correctly you will still get drive but at higher revs. Even if it's 0.5mm to wide with a new clutch the revs will increase, I know because I tried a test on the wife's car.
If it is set up for the correct gap and has the minimum shims on a worn clutch you will still get drive because the rollers will go out further. If the clutch is well worn with this setting the revs would increase while driving. You can get the clearance correct even with 1mm shims in place but then it is definately time to replace the clutch otherwise you will get the rivets eating in to the flywheel. I would say 1.5mm shims minimum as a safety measure and then get the clutch changed as soon as possible.

From new the wear limit on these clutches is small, only a couple of mm.

[volvodspec]

you can have high revs under driving OR under taking off, and copied from the startpost:

hi i have a 340 GL cvt 1990, but it seems to be revving realy high 30mph @ 3000revs

that's higher revs under driving so clutch isn't related to that. however; as pettaw and a few others here suggested; nobody knows a thing about the CVT and espescially if you don't have a service history adjusting/checking the clutch is one of the first things to do

[morgan105]

Another thing to check is to see if the declutching servo switch, the white box located on bottom left wall of engine bay, is working to help the vacuum assist in disengaging the clutch properly and not sticking. Easy to check but requires 2 people. Jack up rear of car and support on axle stands, remove the inspection cover on the clutch release arm then get someone to start the engine while you look at the release arm. This should move slowly and just enough to take up the play in the bearing. With the button pressed on the selector lever it should move a bit more allowing the clutch to disengage.This pushes the plates in the clutch to allow gear change. if it doesn't move then the white box may be bad. White box may also be broken internally and allowing to much vacuum through to the actual declutching servo itself which would keep the clutch open slightly creating higher revs while more vacuum is created while driving.

Are you getting the same vacuum reading on the pipe coming out of the white box servo as the one going in to it from the 4 way valve? The pipe coming out from it should be a lower reading when the button on the selector lever is not pressed.

How is the adjustment on the clutch release arm? If it's to much it may be pulling the clutch open slightly.

If all is working I would still suspect that clutch is either adjusted slightly to far out or worn, or your belts are still a bit slack.

Sorry guys! I know it was wrong, the original post was not supposed to go until I changed the mistakes before submiting but got called away on a emergency and hit submit by accident instead of preview and save and never got around to it till now, my bad!

[volvodspec]

declutching servo doesn't work that way, the clutch itself purely works with the 3 rolling weights that move the pressureplate to the flywheel and engage the clutch by centrifugal force.
all the declutching servo does is pull the pressureplate a bit back; enlargening the distance to the flywheel so more revs are required for the clutch to engage, this comes in handy if you have just started the engine and it's running above normal idle due to the choke

[macplaxton]

is working to help the vacuum assist in engaging the clutch.

DIS-engaging the clutch.

It works as Volvodspec says. If everything in the clutch disengagement servo set-up works, pressing and holding the button on top of the lever will counteract the effect of the mechanial weights and prevent the clutch engaging until the revs are knocking on 2k.

[lewy]

Thanks for the info on testing the clutch system, i shall give this a go at the weekend and let you all know how its going,

did a new post on stripping down the EMV restrictor valve from the Emv, that has made a difference with a new spring, and adjuster srew, the vacc is now 450mBar on the overdrive side.
just hope its the right thing to do?
lewy

[pettaw]

Just to echo the other comments on here, all the de-clutching servo does is push the release bearing into the clutch slightly more so that instead of engaging at 1100 RPM it engages at approx 2500. Honestly don't bother fiddling with the vacuum system any more, just get onto the clutch. I bet you it'll be beyond limits if you need to leave less than 1.5mm of shims then change the clutch. TBH I'd be tempted to say change the clutch anyway, then at least you know where you're starting from.

Like I say one car we did the clutch plate had actually worn down past the rivets and down to the metal skeleton underneath!! And the car still had drive, it just revved like hell!!!

[volvodspec]

they do last a bit longer than that, if you have a correct airgap without shims then you can still drive around 3k miles. no drive is even funnier, pressureplates broken in 3 pieces, rivets and metal all gone, blue colored flywheels etc.

lewy, do you have higher revs at driving off or does it take off normally and then the revs increase?