G60 Vacuum leak ?

[stevemac 0]

This should get you all checking your G60's out.. :onfire:

 

After following the proceedure below, I get a reading of approx 720 (cold) and approx 450 (hot). Suggesting that I have a vacuum leak.

 

Does anybody else have/had this problem ? Any likely areas for the leak location ?

 

 

 

1. Start Motor

 

2. Move the MFA selector to "2"

 

3. Press and hold the MFA end button (keep holding)

 

4. Stop motor

 

5. Start Motor

 

6. Release the MFA end button.

 

7. Press the MFA End button one time.

 

 

You should now see 84-104 readings fluctuating with idle. Anything higher than 104 is not right (vacuum leak). Much less than 84 is probably too much timing advance.

 

Info taken from http://www.snstuning.com

[olly elworthy 0]

mine is about the same,, cant find a leak anywhere though, anyone know where it is most likley to be?!!?

[MT 0]

Yeah mines about those values aswell, doesnt seem down on power and still makes decent pressure on full boost. Any idea if those figures (84-104) are correct??

[olly elworthy 0]

hey that sns site is a us one, maybe the us spec ones are different?!?!

[G60 0]

vac line to brake booster, vac line to gauges, carbon cannister, little hose from intake mani to ISV.. all good places to start

[olly elworthy 0]

G60,, is yours showing 84-100ish then?!?!

[G60 0]

no idea. never checked. but those are all likely candidates for a leak. a vac leak is a vac leak. either you've got it or ya don't. after 10-13 years the vac lines in our cars are turning to shite... time to replace.

[olly elworthy 0]

yeap had to replace the one to the ecu the other day, it was degraded to nearly nothing in one place,,,,

[G60 0]

ya i did that one too a few months ago... i messed around with some wiring back there and i must have bumped it too much... noticable power loss for sure. pulled the hose, it was mushy on the manifold end. replaced it (exactly 1 meter please) and the power came back. this hose is critical.

 

if you still have the carbon cannister, yank that shit off of there and toss it in the garbage. there's 1-2psi right there... and now you can use the carbon cannister hole for a cold air intake feed.

[stevemac 0]

G60 - would it be possible for you to check these readings from your car ? I'm assuming that the Canadian & US spec will be fairly similar. It may just help to confirm wether the readings really should be different to UK spec cars.

 

Don't think this particular problem is related to the ECU vac hose as mine is only 4 months old and I re-checked the condition, connections & routing last week.

 

What I'm trying to work out is wether I have a vac leak or not - if the readings that I'm getting are standard for UK spec cars then I have no need to waste time looking for a leak which isn't there.

 

I'm running a R1 charger & 68mm pulley if that makes a difference ?

[G60 0]

sorry, car's apart... no starting for meee! :?

 

do you have a cam? do you have a boost gauge? what is your timing like? you can get a rough idea if you have vac leaks or not by seeing what your vacuum is like at idle... but this can be affected by cam and timing. stock motor should be around 17-18... mine's 11 but a) i have a cam b) my timing needs to be reset c) fairly positive i have a vac leak. however, 11 is reasonable for a car with a cam so who knows. guess i'll find out as i keep pulling it apart.

[stevemac 0]

G60 - sorry to hear your car's not well, hope you get back on the road soon.

 

do you have a cam?

standard cam

 

do you have a boost gauge?

nothing other than MFA

 

what is your timing like?

shedloads of power so if it's not spot on, it must be very close

 

 

I suppose my original post was just to see if anybody else had experienced the same specific problem & how they solved it. Looks like I'm gonna have to do some testing this weekend.

 

I'm just trying to get the car running at it's "mechanical peak" before I go for another re-chip.

[J a m e s 0]

mine idles around 450 aswell, goes down to 230 when changing gears.

 

can only hit 1460-1510 top at the moment though :(

[stevemac 0]

Looks as though 450 is about standard for UK spec cars. Everybody that I've spoken to seems to have the same reading.

 

Gonna check my boost pressure tonight when the road's clear of traffic.. :wink:

[G-Lader 0]

G60 - if im reading the thread right, you say you gain 1-2psi by junking the carbon canister? Or is that just if its leaking?

I thought the only benefit from junking is if you want to mount the air filter in the wing for better 'breathing' ?

[G60 0]

stevemac: yeah, sounds like your car is good.. was just offering another way to test its health. my car... ya really is too bad. i spent spring/summer working out the bugs that i still hadnt gotten to, finally get it sorted so she's runnin NICE one saturday afternoon, go to pick up the girlfriend from the mall and on the way back the car just shuts off. smoke, etc... a wire from the ignition switch to distributor must have grounded or something cuz its burnt all to shit. need to pull that wiring all out and redo it. :? not to mention that i've been planning a full respray and engine/tranny rebuild so i figure now's as good a time as any. anyway.. sorry gettin off-topic.

 

harry1000: well, i didnt see any gains from the carbon cannister delete, but i wasnt really paying attention and i also deleted the isv at the same time. if you're wondering if its good for any psi increase, just plug the hoses like you would if you were taking it out, go for a run and see how she does. if there's no gain just hook at all back up... if there is, pull that old garbage outta there. :lol:

[funky 0]

does anybody know the best way to check for a boost leak ?

funky

[G-Lader 0]

G60 - thanks I think I'll do that.

Remember checking the full boost output on the MFA when there was a thread with a link to the conversion of MFA no's to actual boost in PSi,at the time my car came out well under (2-3psi under)what the guide suggested a new stage 4 with 68mm pulley should do......I put it down to accuracy of MFA and the diff. degrees of Jabba's work on individual charger porting.

 

Could it have meant I have a leak or does the MFA take the output direct from the Charger so no leaks can alter the charger output?

 

Cheers (hope im not confusing you too much)

[G60 0]

theres a procedure for making a boost leak tester out of pvc tube and a bicycle pump on the CCA website. bad spots are down in the joints with the IC. vac leaks.. well get a vac/boost gauge first of all.. know what cam you're running and what the vacuum should be at the timing you're set for. other then that.. i'd pull those old vac hoses out and replace them if you suspect a leak. i get hose from the stealer at trade cost but people say its too much $$$ there so source 3.5mm vac hose wherever you want.

 

the proper place to tap into the vac system is in the vac line *behind the gauges* pull out the gauges, or go at it from below and you'll see a little vac line, was white in my car. my boost gauge taps off the extra spot freed up by deleting carbon cannister... but the best spot is behind the gauges. you'll be able to check/replace that vac line while you're in there. if that vac line is toast the mfa goes weird.

 

my advice, everyone with a G60 go get an air fuel gauge ($27USD from summit racing) and a vac/boost gauge for your car if you haven't already. xmas present :lol:

[G60 0]

oh and harry... the mfa takes vacuum/pressure reading through a line from the intake manifold, the white one i mentioned above.. if you have a leak anywhere in the vacuum system or boost intake tubing/IC it will affect the pressure build-up, and the reading you get on the mfa.

[stevemac 0]

if you have a leak anywhere in the vacuum system or boost intake tubing/IC it will affect the pressure build-up, and the reading you get on the mfa.

 

So would I be correct in thinking that if the mpg readings are accurate that I am unlikely to have a boost leak ??

 

Alternatively, would the increased boost pressure provided by R1 charger, 68mm pulley affect the mpg readings in any way ??