MK4 Golf PD150 Strange Cabin Smell

[Iam Keyser Soze]

Hi everyone. My names Ben and this is my first post.
I have 2002 MK4 Anniversary TDI Golf(67k miles) Over the past 12 months it has developed a strange smell in the cabin.
It only seems to appear when the cars hot and I'm pretty certain its affecting the performance too. I can best describe it as sweet sickly oil smell. Could even be exhaust fumes? What's the difference in smell from exhaust to boost leaks?
Dropping the windows usually makes it more noticeable . Driving with the air on on recirc does help a little but I'm looking for a permanent fix.

The car is remapped with standard exhaust and has the Allard EGR Delete and full SFS hose kit.

So far we've changed all the intercooler and boost pipe seals. Fitted a new intercooler and pancake pipe as both were split. Checked all the exhaust for leaks and fitted a new turbo manifold gasket. New genuine MAF. We even fixed a gear oil leak just to be sure.

It's really starting to annoy me now and wondered if anyone has any ideas?

[geoff eeles]

Hi Ben. Have you checked the aircon gas? Have any of your passengers not been washing properly!!!!

[Iam Keyser Soze]

Hi Ben. Have you checked the aircon gas? Have any of your passengers not been washing properly!!!!

The air con was regassed when the new intercooler was fitted.
It's definitely a mechanical/ fume smell and not a person.

[Crasher]

If recirc makes it better that suggest engine bay fumes are being drawn into the heater but opening the window making it worse reminds me of one I had like this which turned out to be the tailpipe design on the aftermarket back box, it took a long time to track that down. You have a standard box so it is not that. Is the crankcase vent pipe connected in the normal way?

[Iam Keyser Soze]

If recirc makes it better that suggest engine bay fumes are being drawn into the heater but opening the window making it worse reminds me of one I had like this which turned out to be the tailpipe design on the aftermarket back box, it took a long time to track that down. You have a standard box so it is not that. Is the crankcase vent pipe connected in the normal way?

Thanks for your reply. When you say crankcase vent you mean the flexible pipe that goes into the top of the rocker cover? If so then it's still fitted.

Would a slight leak from the tandem pump cause this issue? Would it affect the cars performance?

I also keep hearing about some vents that are behind the back bumper area not venting.

[Crasher]

Any fumes in the engine bay should not get into the car through the heater so the engine bay to plenum sealing needs checking which is various different seals. The rear vent trims (3T0 819 465 £10.26) cab fail and the one on the left will allow exhaust fumes in.

[Iam Keyser Soze]

Any fumes in the engine bay should not get into the car through the heater so the engine bay to plenum sealing needs checking which is various different seals. The rear vent trims (3T0 819 465 £10.26) cab fail and the one on the left will allow exhaust fumes in.

I've since replaced the two sponges that sit on the wing edges next to the scuttle seal (1J0 823 729) and both the rear vents behind the rear bumper and I'm still getting this smell.
Where could I view a diagram of the plenum to engine bay sealing?
I'm starting to think the smell is possibly boost fumes as performance is affected and it does feel down on power. Feels like boost has moved right up the rev range and requires quite a lot of pedal in order for it to perform. I have the full SFS intercooler and turbo hoses so there shouldn't be an issue like the standard Vw pipes. I have a new intercooler and pancake pipe as both were split. New green seals have even used throughout too. MAF was replaced with a gen vw item last year.
Tandem pump is leaking slightly so the seals are being replaced next week but I can't see this making a difference?
Any more suggestions would be greatly appreciated.

[zollaf]

sounds like you have a boost leak.

[Davew64]

Hello. I'm new here and this is my first post. I had this Issue and the fumes were coming from the flexi. I had the downpipe changed and all fumes now gone. Hope this helps even if it's many years too late.