Thread: Boost gauge problems

I installed my boost gauge into the back of the intake manifold.
On mine there was a brass bolt/plug at the firewall end, pulled it out and got an adaptor from Queensland diesel spares.
On idle it reads 0 psi, full boost 19 psi.
Where you tee'd it in should be OK.
Not sure the oil will have any effect

Originally Posted by mickashay

I fitted a electronic boost gauge to my 300 tdi engine but am having a few problems,I tee pieced the small black plastic pipe at back of turbo,I noticed this had a small bit of oil in it and doesn't have any air flow ? I'm think ing it's the wrong hose but looking around the forums it's right,gauge reads -14psi when car is of and about -11 when idling and not changing at all when turbo kicks in,any advice with this please

Sounds like you have tapped into the Vacuum line that is used to regulate the turbo vanes. your measured negative boost is vacuum.

You have to tap boost from the pressurised air intake path... between the turbo and intercooler OR intercooler and engine intake.

i dont think im tapped into a vac line,its reading -14 even when the car is not running and no vac would be running through the line,i have found the plug at the back of the manifold and if i can get a fitting i will change it to there,i took a pic of where i t pieces the line to show if im right or wrong and a pic of the plug to be sure its the right one,does anyone know what size thread it is so i know what to ask for
thanks mick
this pic where i teed into the line

and this one where the plug is

Originally Posted by mickashay

i dont think im tapped into a vac line,its reading -14 even when the car is not running and no vac would be running through the line......

this pic where i teed into the line

Yeah the hose is not for boost. It connects to the top of you fuel injector pump (pressure regulator ??) and the Tees off to the engine hence all the oil.

Yes use that brass plug on the firewall side of the intake manifold.
I have not removed mine but it looks like it has a bit of plumbers Teflon tape around the thread to help seal it. You could just unscrew it and take the bung to a hydronic store like Pertek and they will have a suitable reducer and barb fitting to tap boost from. Pertek is we're I have got my last 2 brass fitting for tapping boost on my other VW tdi's.

Looks just like a 300tdi to me and that's the hose going to the ip should be fine. While you are in there check the other hose comeing off the brass fitting to the wast gate these can split and Leak

as above. you have teed into the boost sense for the ip anaeroid. that line should be reading boost made at the turbo

by measuring boost at the manfold you are measuring what the engine sees ie after inter cooler and hose work

your readings seem whackyif gauge is good check all lines . ensure no leaks. perhaps check the aneroid diaphragm. oil in that line is in your induction supply. could be from turbo but more likely from blow by. id be pulling the induction hoses and ic down for a clean.

ps. the only vacuum on a 300tdi is from the vac pump for the brake booster

steve

Thread size is M12
There is a copper washer under the head of the existing bolt, I reused it.
Get a standard M12 to 1/8 adaptor for the air line.
They had them on the shelf at QDS. They are just standard airline fittings as used in trucks/buses.
I'm thinking your gauge is suspect. Is there a reset on it ?


PS-your heatshield is missing, Just like MINE