Xc70 suspension mounts
 

Hi have the familiar popping sound from the oil filler cap. With my old v70 it was easily diagnosed as engine mounts.

However, with my 2008 I'm not sure it's the same problem. It's a d5 as was the v70 but different generation.

Anyway to tell if its defo engine mounts and if it is, is it the same change process as my 2006 v70

My car doesn't have vacuum engine mounts (2007 S80 P3). As my car is basically identical underneath to the V70, I suspect this will be the same for your car. However, you could have a leak somewhere else in the system...

The P3 platform still has a vacuum pump though, but the turbo's aren't controlled by vacuum like the older P2 euro 3's (euro 4 turbo's are electronically controlled). Leaking engine mounts on the older euro 3's could cause turbo boost issues, which in turn affected performance. This isn't the case on the euro 4, but as there's still a vacuum pump, there still could be a vacuum issue if you're hearing a popping noise (brake booster seals, vacuum pump seals, pipework etc) are possible culprits.

Watch this video, which shows testing the vacuum pump in more detail. Its from an older euro 3, but the process is more or less the same.

https://www.youtube.com/watch?v=-lgYAS3GoiE

Ok, so basically find the vacuum pump and check it's not leaking like in the vid?

A slight popping noise & a bit of white smoke is normal for a D5. A loud popping noise isn't, as explained in this video;

https://www.youtube.com/watch?v=QHLyubTrIQ8

*Note, I don't think your car has vacuum engine mounts (my car doesn't & its identical to the V70 in terms of engine layout & suspension & the XC is similar too). I'm fairly certain you won't see a vacuum pipe going to the engine mounts from the turbo control valve (like shown in the video on a euro 3), as yours is a euro 4 & it doesn't have vacuum mounts as far as I know (double check this though). The turbo is electronically controlled on the euro 4 & not by vacuum like the earlier euro 3's (this is why vacuum issues don't affect performance as such on the euro 4's). However, if you hear quite a loud popping noise from the oil filler cap, there's some sort of vacuum leak somewhere else in the system (rule out the vacuum engine mounts though possibly because as far as I know, there isn't any (double check).

This video shows how to directly test the vacuum pump. If you do this test as shown & the needle on the gauge is flickering, then that indicates a leak with the vacuum pump itself. The seals in the pump can be replaced, or you can buy a new pump. If the needle remains steady, then the pump is fine.

https://www.youtube.com/watch?v=-lgYAS3GoiE

If there's no vacuum loss at the pump, then you need to test each part of the system by checking the pipes for any wear as you go along (which would cause vacuum loss) & hooking up your vacuum tester to each section of pipework to check the reading (check for a flickering needle, which indicates a leak in that particular section of pipe. If the needle remains steady, that section of pipe is okay). Then its a case of keeping going & testing each section of pipe as you go on, until you eventually find the culprit(s). You may come across split pipes, which have just worn out due to age & being in a hot engine bay. If you're lucky, you might see split pipework early on. Its not a five minute job testing the whole vacuum system, so allow time.

https://www.youtube.com/watch?v=0zsIa4Y2Tcs

Note, these videos are from a euro 3 car. The process is more or less the same in the euro 4, except you don't have vacuum engine mounts (as far as I know) & the turbo is electronically controlled (so there's no boost solenoid).

Thanks to cheshired5 for these helpful videos too.

So how does one accertain if the popping is the standard volume or excessively loud?

Watch this video. You'll be able tell the difference between what is "normal" & what isn't.

Note, this video shows a euro 3 engine. The differences in the vacuum system are explained in my other posts above.

https://www.youtube.com/watch?v=QHLyubTrIQ8