D5 - changing engine mount affects turbo response.....?

An interesting one, which I would appreciate feedback on........

Ive just changed the top engine mount on my 162k miles D5 163. It was wearing an 'original' round type one and it was absolutely GOOSED. The bloody thing fell apart in my hand when I had it off the car. Its now replaced with a shiney new 'square' type.

Apart from curing the bloody rough idle (yay!) its also cured the 'dump valve' sound and lazy turbo I have been experiencing.

The dump valve sound was incredibly noticeable, like you hear on ricer wagons etc and now its completely gone - the turbo is also much quicker to respond, especially when coming on/off the gas at speed in 5th gear etc.

Something has obviously changed, nothing else on the car was touched - the difference is like night/day and im just wondering what has done it.

Ta!

Bit of a weird one that. All I can think of is that without a good top bush, the engine leaned back a bit more than it should, causing a gap to open, somewhere between the airbox and the turbo. the new mount may have sat the engine foreword a bit, closing the gap.
To hear the recirc valve, there must be something letting the noise out, like a gap or high-flow air filter. Did you remove any of the air pipes to fit the mount? you may have re-sealed a hole that you didn't spot previously.

I noticed I had a 'pending' code in the OBD for an incorrect MAF value - one of those ones where it doesnt illuminate the engine light unless its recorded X amount of times over X amount of engine starts.....

I think you might have explained it :)

Well, without the top mount being in good order, the engine will thrash about badly while driving. All that movement could potentially affect fueling, maf readings, Lambda readings etc, not to mention the backlash on the driveshafts, diff, dmf etc.

The only way you'd be able to hear the turbo/recirc would be if there was a gap somewhere and since you say you had a performance increase after, I'd say the gap was between the maf and turbo, causing dodgy maf readings.

I managed to overwrite my previous reply with my last reply - doh!

Anyway, read the post above - I think you have explained it :)

My guess, from experience, is your turbo is hanging off the manifold. The new top mount is stopping the engine flapping. Look down the back from the top and make sure the two nuts are tight at the top. Next time it's up in the air look up at the turbo and check the bottom nut is secure.

Hi,

Which bolts do you mean exactly?

The only bolts I can see when looking down from the top are the stud bolts that pass through the heat-shield........

Thanks

Hope this helps.

http://i4.photobucket.com/albums/y13...SCF8309red.jpg

Ooh, good point Mr. Redbrick.

Thanks for the pic, very kind.

Is the heat shield a pain to remove? Looks like thats the only way to get at those bolts, correct?

Mine is a 163 Euro3 and AFAIK never came with a heat shield unless someone removed it and never put it back on... There is also another nut that you can only get at from underneath by reaching up, obvious when you look up there. Mine have worked loose twice now and I've bought new nuts to stick on when I have five mins, not surprisingly it is far less laggy with turbo attached! lol

Also my 'new' square top torque bush is now split!!!! More money :(

The 3 bolts are absolutely fine - toight as a toiger.

The heat shield came off easily, not sure it will go back on quite so well :)

I dropped a spanner down the back of the turbo, meaning I had to get the car up on stands and the undertray off to remove - doh! However this gave me a quick excuse to have a poke around down there - I hate being under cars, even on stands.....

Everything looks tickety-boo. Absolutely no oil residue or gunk at all, so I think everything must be working reasonably well. The condition of the engine bay in general belies the 162k miles completely. It hasnt used a drop of oil or coolant in the 9k miles I have had it either, so im guessing the PO must have changed the intercooler (at least) at some point.

Some pics from on top and from underneath the turbo........

Clean as a whistle!

http://img.photobucket.com/albums/v7...308Large-1.jpg

http://img.photobucket.com/albums/v7...51221Large.jpg

Im leaving the heat-shield off for now - i presume that will have no ill effects?#

Ta!

Quote:

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Originally Posted by M-R-P

Bit of a weird one that. All I can think of is that without a good top bush, the engine leaned back a bit more than it should, causing a gap to open, somewhere between the airbox and the turbo. the new mount may have sat the engine foreword a bit, closing the gap.
To hear the recirc valve, there must be something letting the noise out, like a gap or high-flow air filter. Did you remove any of the air pipes to fit the mount? you may have re-sealed a hole that you didn't spot previously.

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you can always here the recirc valve on the D5 engines - it is normal . i suspect feedback of noise throught the intake pipe/ air filter because it sounds the same as if you fit a pipercross induction kit on a petrol turbo.

Quote:

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Originally Posted by partsforvolvos.com

you can always here the recirc valve on the D5 engines - it is normal . i suspect feedback of noise throught the intake pipe/ air filter because it sounds the same as if you fit a pipercross induction kit on a petrol turbo.

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Yep that's kinda what I'm basing my replies on, although I've heard mine when the inlet pipe was half - off the turbo. That made some interesting noises lol.

What's really confusing me about this is that changing the mount has had an effect on sound an performance, which is why I suspected a gap/hole/crack in the inlet pipe from the airbox, made worse by the mount not holding the engine correctly, causing extra noise and unmetered air to enter the system.

Thanks for all the help with the trouble shooting chaps.....

The car spends 99% of its time with me outside the UK, but im back in late October and its booked in at VolTech in Hull for new rear discs and handbrake shoes and a general going over / diagnostics report. Ill get them to give the intake, turbo and vacuum system a once over at the same time.

Im going to keep a beady eye on it in the meantime to see if there are any discernible changes over the coming weeks.

Happy to help.
Not that this will be anything to do with your current question but have you had your mixer pipe cleaned recently? If you're doing a lot of miles, a clear mixer pipe will give you a smoother drive and better economy.

Quote:

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Originally Posted by M-R-P

Happy to help.
Not that this will be anything to do with your current question but have you had your mixer pipe cleaned recently? If you're doing a lot of miles, a clear mixer pipe will give you a smoother drive and better economy.

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Indeedy - I gave the EGR mixer a clean in July..... ooh it was a messy, clogged up §§§§§§. I gave the turbo control valve on the front of the block a good clean about 3 weeks ago as well.

I did my mate's 2002 D5 mixer a while back. It had NEVER been done...
http://i1100.photobucket.com/albums/...6022E-orig.jpg

http://i1100.photobucket.com/albums/...AFAB1-orig.jpg

http://i1100.photobucket.com/albums/...46CAB-orig.jpg

Hells bells, this thing was NASSSTY!

Here's a pic of what we scooped out...

http://i1100.photobucket.com/albums/...6F0CE-orig.jpg

Quote:

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Originally Posted by M-R-P

Yep that's kinda what I'm basing my replies on, although I've heard mine when the inlet pipe was half - off the turbo. That made some interesting noises lol.

What's really confusing me about this is that changing the mount has had an effect on sound an performance, which is why I suspected a gap/hole/crack in the inlet pipe from the airbox, made worse by the mount not holding the engine correctly, causing extra noise and unmetered air to enter the system.

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indeed, replacing the top mount ought not to be related . strange things, cars!