So my wagon sat for near on a year due to various hold ups with my engine rebuild. In that time the brakes turned to crap and had become a little spongy so I bled the brakes with all new fluid. A quick run around the block and a short drive seemed to show that things were back to normal, however whilst out on a longer drive when I came to slow down for an intersection I found that I had apparently lost brake boost and had a very hard pedal. The pedal seemed to go back to normal when I pulled the gearbox out of gear. On the drive home the above situation happened on about 10% of the times I had to brake.
Any suggestions as to what might cause such an issue? I would have thought that loss of vacuum would either be 'gradual or gone' and not random.
Well there's really only three things it could be - the hose to the booster, the check valve on the booster, or the booster diaphragm. Check the hose for leaks but it seems more likely it'll be the check valve or diaphragm, in which case you'd want to just replace the whole unit.
If you find it annoying, in the meantime you can just disconnect the vac line and run with no booster. It seems hard at first but after an hour or so you'll be 100% accustomed to it and won't notice.
What cam are you running? Could you just be losing vacuum due to high rpm?
I've got twin webbers and a cam similar to the street performance cam.
Off the top of my head its been happening at cruising rpm mostly.
How "angry" is the cam? Do you have a vac/turbo gauge kicking around that you can hook up to see what vac is doing at the times it is loosing vac boost?
I was just thinking that myself. Assuming thats the case, what is the usual fix?
Awesome, thanks. My engine bay real estate is being eaten up quick!