The factory o-rings in your fuel system are made of Buna-N elastomer. Buna-N was fine and dandy for most all fuels before ULSD, ethanol and methanol. With today's fuels and additives the Buna-N gets fuel permeated (saturated) and begins to break down the elastomer at a molecular level. In this new state, Buna-N will expand and contract much more than when they were new. When the engine gets cold, they contract and fuel will leak between the valve and the fuel bowl or just seep around the o-ring and find its way out down the drain tube.

You can go to Ford and buy a new valve for what? $50 to $65 and get the same ol' crummy Buna-N o-rings and do it all over again in 2 or 3 years.

The automotive world has many other elastomers available to their purchasing departments that are far superior to Buna-N. I need someone to explain to me why they continue to use Buna-N as their fuel and lubrication seals. Viton has proven itself to be much more reliable and able to outperform and outlive the inferior Buna-N material.

Hissing? Probably your Exhaust Backpressure system closing off the turbo outlet in an attempt to warm the engine. You may want to check out the article in my sig line about cleaning the EBPV sensor line just to make sure that you don't have a plugged or cracked sensor tube.

 

Thanks, great explanation. I guess my tiny mind just needs to understand why things happen rather than just changing parts to see what happens

 

Well, i did it yesterday. Fixed my leak. ordered the fancy $6 orings from dieselorings.com, followed the directions and worked like a charm. Very satisfying knowing i fixed it my self and saved 194$ is an added bonus. The local diesel mechanic here wanted $200 to fix the leak.

Added advice on the directions...unhook and move some of the wires from the relays and such (i dont know what they are) so you can have better access to the valve. Makes it much easier.

 

Just a questtion but Just how would this be Brand Bashing?? He simply tells you 2 ways of a fix. We all know how much 2 O-rings would cost and he is telling you how much about it is from Ford.