We have an old but otherwise good condition 240 that has developed strange behaviour intermittently when braking, and to some degree steering. To simulate the symptoms, when the vacuum hose is taken off the brake servo and then shut off by sticking my thumb on it, the engine revs drop and it splutters trying to stay alive.
So far we have replaced the brake servo and master cylinder (plus all pads, bled through new fluid etc.). This did help for a while but the problem persisted, so we installed a 2 litre vacuum tank with an electric pump running off the battery, so when the servo is calling for the vacuum it gets it from the tank if the manifold can't provide it. You can hear the pump kicking in and topping up the tank when the brakes are applied, this helped for a while but the problem still happens.
We took it to the local Volvo garage for their assessment and they tweaked the carburettor so that it was idling a bit higher, but we got the impression they didn't want to spend much time on such an old motor. This has helped a bit, but still the problem remains.
An example - drawing up to red lights, gently on the brakes, still in 'drive', now stationary for a few seconds the engine revs start to fall away and then it will stall. If I put it in nuetral, and catch it quick enough I can rev the engine back up, this is ok when stationary, but it also happens sometimes if braking while turning (asking for more vacuum?) on e.g. a roundabout, where it is a bit trickier to keep the revs up.
Finally, this behaviour only happens after the engine is up to temperature, and more frequent the longer it's been running. When it's cold and the choke is out the revs are up anyway so it doesn't happen.
Has anyone experienced something like this? Any suggestions would be great, as otherwise the car is in great shape for it's age.
Thanks for reading
So far we have replaced the brake servo and master cylinder (plus all pads, bled through new fluid etc.). This did help for a while but the problem persisted, so we installed a 2 litre vacuum tank with an electric pump running off the battery, so when the servo is calling for the vacuum it gets it from the tank if the manifold can't provide it. You can hear the pump kicking in and topping up the tank when the brakes are applied, this helped for a while but the problem still happens.
We took it to the local Volvo garage for their assessment and they tweaked the carburettor so that it was idling a bit higher, but we got the impression they didn't want to spend much time on such an old motor. This has helped a bit, but still the problem remains.
An example - drawing up to red lights, gently on the brakes, still in 'drive', now stationary for a few seconds the engine revs start to fall away and then it will stall. If I put it in nuetral, and catch it quick enough I can rev the engine back up, this is ok when stationary, but it also happens sometimes if braking while turning (asking for more vacuum?) on e.g. a roundabout, where it is a bit trickier to keep the revs up.
Finally, this behaviour only happens after the engine is up to temperature, and more frequent the longer it's been running. When it's cold and the choke is out the revs are up anyway so it doesn't happen.
Has anyone experienced something like this? Any suggestions would be great, as otherwise the car is in great shape for it's age.
Thanks for reading