OK... I took the manifold off and discovered that the black hose that leads from the firewall to the preheater was leaking at the connection to the preheater. I cut off ~12mm and reconnected. I no longer have a hooka effect (i.e. there is no bubble steam in the clear tubing between the preheater and the prefilter.) However, once I turn the car off, there is a bubble that forms at the prefilter and moves back along the clear tubing towards the preheater. Is this due to a leaky seal at the prefilter? I'm guessing this is the case but as my parts haven't arrive from Spokane yet, I will be quivering with anticipation...

Thanks for the tip on this!

-l-

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'84 300d turbodiesel (83K miles)
'96 300d (226K miles)
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other fine diesels...
'99 Polaris diesel (Fuji Heavy Industries single)
'01 Diesel Trail gator (Yanmar triple)
'95 John Deere 970 (Yanmar quad)
'11 BMW 335d
'12 VW Jetta TDI

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'00 BMW K1200LT
'02 BMW R1150RS

'15 BMW R1200GSA