2004 V70 D5 Popping Sound - Brake Servo?
 

Hi

I know this subject has been the matter of many threads, and with the help of SiRobb's videos I've done some diagnosis.

My engine mounts are in need of replacement, so I've blocked off the vacuum line with a bolt and cable tie for the time being. Even with my finger on the vacuum port of the pump the popping noise remains. It pulls 23inHG at the vacuum port on the pump which I think is plenty.

When I unplug the brake servo pipe from the vacuum pump (i.e. massive vacuum leak) the popping noise stops completely, if use my finger to block the port and its pulling so much vacuum it hurts my finger, but the popping noise continues.

This would seem to me to be the wrong way round, but the conclusion is with both ports on the vacuum pump blocked I get loud popping, if I leave the brake booster port to atmosphere it's as quiet as a mouse.

Edit to add - if I remove the vacuum pipe from the servo and block the end I get massive vacuum, so the pipe to the booster is definitely good.

Does this mean my vacuum pump is toast? Could it be a fault with my servo? The brakes feel fantastic and pedal is firm, and no hissing from the footwell etc.

Any advice welcome, thanks.

Just a cheeky bump.

It would be helpful if anyone could confirm their if their popping noise is present with both the vacuum port and brake servo port blocked off, just to see if mine is behaving normally? It does seem odd to me that its really noisy with both ports blocked, but quiet with the brake servo port open to atmosphere.

I can get a video if it helps clarifies things? :thumbs_up:

I knew it reminded me of a couple of threads but no clear conclusions unfortunately. Some of the tests may offer you something though.
Think long and hard about fixing something if nothing appears to be broken and your only symptom is the noise.
I would also check for the popping noise at different engine temperatures.

https://www.volvoforums.org.uk/showthread.php?t=269693

https://www.volvoforums.org.uk/showthread.php?t=264268

Thanks Simon.

Great advice on checking at different temperatures, when the engine is up to operating temp its quiet as a mouse with the servo connected as usual and the other vacuum port on the pump blocked off. The servo operates as expected and I have no other concerns, so I'm going to replace my engine mounts and forget about the popping on a cold engine :thumbs_up:

Thanks again.

Hey Tomoose,

I have got the exact same symptoms!
Have you found any solution / the flaw?

Best Regards, Konstantine

could it be the one way valve not working as it should,
Dave

Why should the popping stop when the brake-vac-hose gets detached?
Also, the popping comes back when the vac. port is closed. That would
exclude the one way valve from being the cause of the sound.
this does not make sense to me... Brake servo performance is very good.

Hi if popping stops with the brake vac line disconnected, if the pipe from the vacuum pump is not plugged to stop leaks, then you will not have any vacuum
take the brake booster pipe off the vacuum pump and plug/seal the that port on the vacuum pump, if you still have popping it is nouthing to do with the brake booster or one way valve,
and you have a leak some were, as the vacuum pump is always running with the engine you only need a very very small leak, WITH A BIG LEAK THERE IS NO VACUUM
so get a mityvac hand pump to test all pipes and engine mounts and solenoids and turbo actuator, with the hand held pump you can apply the vacuum an then stop pumping and see if the vacuum holds,
if you try and do this using the car vacuum pump it will be very hard to do as it is always trying to make vacuum,
you could do it with the cars pump and a gauge but you would have to block the pipe from the pump and disconnect it from the pump and make shore it is not leaking there,
so it is bet to use a mityvac hand held pump with gauge,
Dave

Hello Konstantine,
I have the same problem as you described it, the popping noise dissapears when I disconnect the brake vacuum hose and it's back when I reconnect it. Can you tell me what was the problem in your case?

The vacuum pump only pops when it gets a little air.
The brake booster port has much bigger diameter compared to engine pad valve and turbo solenoid port so both sides of the pump get close to atmospheric pressure and therefore the popping stops.