Volvo 66 Engine Braking switch

[Dunc]

Hello all, I am aware that our 66 Volvo variant does/should have an engine braking switch for the driver to operate in order to achieve a kick-down effect and hence gain some engine braking. I have however struggled to identify it on the dash! Where should it be, what does it look like and what sort of switch am I looking for; rocker, toggle, button...?

I should point out that there appears to be one or two things missing from the dash, and there’s a pull-out/push-in button dangling in space! Could this be it??

[swissdave]

Hi Dunc, it's this hill descent switch, it should light up green when switched on. It applies the vacuum to the "change down" side of the Variomatic to keep the gear ratio low and engine revs high. It is the same circuit that is activated by the brake lights switch, forcing the gearbox into a lower ratio under braking.

[andrew]

Yes, the switch reverses the vacuum to encourage the transmission to change down, thus assisting engine braking. Oddly, on Daf 66 cars the green light in the switch goes OUT (turns off) when the brakes are applied, as the same circuit controls both!

[Dunc]

Ok thanks for the help - at least I know what it should look like thanks to the photo. I’ll go looking for it tomorrow when I’m next in the garage! Can anyone tell me if there’s a way of checking that the pulleys aren’t seized onto the shafts and therefore unable to slide? I don’t want to put a lever in there and force them apart if that’s going to cause damage. At present the belts are sagging and the rear pulleys are touching. I know they should be 3mm apart but don’t want to start trying to wind the adjustment bolt if the pulleys are seized...

[andrew]

Be careful very careful when working on the pulleys; the forces involved will crush your fingers if you're not careful! With that warning ringing in your ears, in order to tighten the belts on a 66 you need to undo a large number of nuts before winding the adjuster, so do your research first.

As to checking if the pulleys are moving, would you be able to raise the rear of the car, to ensure both wheels are off the ground? If so, remove the transmission covers, start the car with the selector in the forwards position, rev the engine & use your mobile to video what the pulleys are doing! Even with slack belts you should still see the primary pulleys contracting and the secondaries similarly expanding.

[paull]

Hi Dunc
heres my V66 dash switch layout - left to right
left of wheel : hill switch , light switch
right of wheel on moulding: choke and brakes warning lights, blank switch
right of wheel below moulding: rear screen heater, hazard lights

my spot light switch and rear fog (extra) switch are on the centre console

all of the switches are rockers on mine

this Guy on eBay has some switches listed:
www.ebay.co.uk/str/wharmdavi

paul

[bobdisk]

These videos show what you should see, and, as Andrew says, be VERY careful about the forces of the springs inside both primaries and secondaries.



A review of the 66: Look at 9min 50secs.

[paull]

Another question about the hill decent engine braking system -
Is it’s operation method the same as the kick down switch when the accelerator is pressed fully?

I’m asking as I am not sure that mine is working well - the kick down definitely works but neither pressing the brakes or flicking the switch appears to have much effect in changing the gear ratio - is this just due to not being on the power and forcing the primary cones apart?

[swissdave]

Hi Paull, no it's not the same. All the full throttle position switch does is turn off the "change up" circuit. This change up side of the vario is switched on by the micro switch on the throttle when the accelerator is pressed and the throttle position moves a few mm off of idle. It stays on constantly trying to change the gear ratio higher unless full throttle is applied.
The other circuit is the braking/hill descent side. This when activated applies vacuum to the opposite side of the gearbox and assists changing to a lower ratio. As you realise this is operated by the brake light switch or the hill descent switch.
A couple of things to try;
With the ignition on press the brake pedal and listen for a faint click behind the dash, this is the EMVK valve working
Next switch on the hill descent switch on, it should illuminate but go out if you press the brake pedal.
To see if the braking/hill descent side is working drive the car at about 30 and switch on the hill descent switch. The revs should ride considerably.

[paull]

Thanks Swissdave, I get a slight click from the dash but nothing else when driving along - looks like I’ve got some investigating to do over the weekend.
Luckily the last club mag had a really good article on how the control system works, all I have to do is work out the vacuum connections on the control valve!

[bobdisk]

Look for rotten rubber pipes that are leaking. They are all concerned with the vacuum system. Start at the inlet manifold, control valve, front to rear pipes and also at the centres of the primary covers.