How do you mean blowing? exhaust gases or just a lot of pressure blowing the cap off?
when you remove the oil filler cap and put your hand over the hole it is blowing up bits of oil . its pressure it pushed the dipstick out
pressure blowing the dip stick out
Hi..sorry for the delay..for some reason i didnt get email that you replied?
Ok..From what your saying the obvious place to start is checking for restriction in the PCV system or basically the breather on the engine/crank case breathers..if they get blocked/valve this can cause pressure to build up in the engine and blow the cap off or push the dipstick out the tube..You dont mention if the garage has ruled that out but id suggest they double check that out properly...the only other thing that would cause this too is serious internal fault ie:- pistons rings etc.but usually the breather system would be the best place to start..also ensure the oil level is actually correct and not over filled....I do hope this helps