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Help please ... 6.5td fuel leak after oil change

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seza

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Hi
I am distraught tonight
After changing the oil on my 1994 Chevy sub with 6.5TD V8 from ordinary mineral to 5W-30 full synthetic I have just noticed diesel fuel leaking from the middle of the engine area, am not sure where it is coming from.
I hope to god that I have not damaged the seals on the IP (the old mechanical type)???

please advise as to what to do? if I change back to mineral will that help?
what is worse is that I am the UK where parts and experts are hard to come by.

thank you
 
Sounds like the IP or hoses are leaking, but is unrelated to the oil change. Could be the feed to the IP or the drain line.
Take an inspection mirror and a "torch light" flashlight and see if you find anything leaking. Also the FFM (fuel filter manager) is known to leak commonly at the base. There is an oring there.

Oh yea, Welcome!!
 
Welcome aboard, Seza!

I very much doubt your issue is related to the new oil; follow Leroy's instructions, and look for a line that got moved, or cracked in the process. It's pretty easy for those old fuel lines to get brittle from the heat, wear and tear, etc.

Fill out your signature, give us a little help figuring out what you have there.. obviously, if your 1994 has a mechanical IP, it isn't stock.
 
Did you change the fuel filter with the oil change and now have a leak at the fuel filter? Otherwise it is not related to the oil change.
 
thanks for the coments

Very odd because before the oil change there was no leak whatsoever anywhere,
I did not touch the fuel filter or the lines.
I read elsewhere on the Web that if you switch from mineral to Synthetic this could happen as the synthetic oil can get into cracks and holes that were too small for mineral oil?
I am no mechanic but my understanding is the engine oil cools the IP too?

Anymore comments and/or suggestions are welcome.

I will report back
 
I had a quick look today:
I was none the wiser as to where the leak is coming from, but:

1. the leak (drips) only happen after the engine/oil has warmed - after 15mins driving
2. it seem to be coming more from the passenger side - more drips from starter motor
3. it definitely smells like diesel - there is no doubt about it
4. the car starts and drives fine

any thoughts?
 
Welcome
Any fuel leaks up in the valley of the engine seem to end up on the starter area. There is a drain hole in the valley that dumps into the bellhousing area. The oil or fuel hits the flexplate and or torque converter and sprays the starter. As mentioned the fuel hoses and o-ring seals in the fuel filter housing are suspect. Another possibility is a cracked high pressure injector line or a leaking return line.
 
Sounds like a cracked return line... check all of your passenger-side injectors. There is rubber hose between each one, goes back to a common line that meets up with the return line from the IP.

The problem isn't the synthetic oil... diesel cools the IP
 
I have the same exact problem, but on driver side. It is as Jim said one of the return lines or the cap on the rear cylinder. Noticed it yesterday. Yours leak would be on pass side and might be hard to identify right away because of the turbo and heat sheild.

Edit: Engine oil does not cool the IP. It depends on the fuel for any cooling and luberication. Do you guys have the Ultra Low Sulfur Diesel there also? Its a good idea to use a diesel fuel additive or I like to run 2stroke motor oil.
 
Last edited:
thanks guys, I am already using 2stroke with every fill up,

that is a relief to know that the IP has not been affected by the oil change but I still have to find out where it is coming from esp with fuel prices as it is now!
 
You need to start top down to find the leak. It can only come from the injectors, IP, filter in the engine valley, or supply and return lines. Start by checking the injectors and return lines for wetness. Then check the supply and return lines behind the fuel filter. Then check the fuel filter assembly. While checking that you can see where the engine valley is wet at -if.

The IP can leak fuel from the front seal while cold. Engine running you may see a drip from the front of the IP.

The exhaust manifolds can vaporize the diesel and make a leaking return line hard to find.

Just check everything and keep in mind you may have more than one leak.
 
Thanks WarWagon, not the easiest of engines to work on as all the suspect parts you listed are either hidden or inaccessible without disassembly,
any tips and hints as to how to go about it will be appreciated.
 
Well, it seems like the leak is coming from the valley of the engine because it all look damp there incl the pipe that comes to the shut off valve
near the alt, so I am not sure if it is the pipe or the IP?
 
Had the same deal earlier in my "What's a diesel" education. I'd done some unrelated work to the fuel system but had disturbed the lines which were old and had weakened at the clamps and started leaking.

Is the line to the drain/T valve wet at the valve and leaking which is running back down the line to drip into the valley? Could be the Valve has failed but that's a real long shot. More likely it is the line has weakened at the valve or at Fuel Filter Manager (FFM). Same with the other rubber fuel lines at the FFM and IP.

While you're at the front of the motor, Check the short rubber injector return line at the front of the motor to IP for the same issues.

Power up the lift pump by jumping it at the fuse/relay box's A or B AUX terminals or key on till the LP stops ticking. Then check the lines for drips while the system is pressurized.

Repair by removing the clamp and the line and inspecting for wear and tear and if the line is leaking at the clamp, trimming back a quarter inch of old damaged line at the connections and replacing the clamp with hose clamps and not the spring loaded factory ones that are prone to fail.
Same with the other lines at the FFM. If it is that short injector return line to the IP, you'll be better served replacing the line altogether as it is only a few short inches and not a lot of room for trimming and refitting.

For the FFM, Remove the 6.5 cover or "Dog House" as it is often lovingly referred to, that sits over the intake manifold if it is still there. 4 10mm bolts IIRC.
Remove the two bolts holding the Fuel Filter Manager on the lower intake manifold, 15mm IIRC. There should be enough play in the fuel lines to lift it up and inspect the three lines from the fuel tank/LP, the line leading out to the IP and the line leading out to the fuel drain valve at the alt. Pressurize the system and check for leaks, trim lines and replace clamps as needed.
If you want/need to replace the lines under the lower intake it’s as easy as using the old lines to pull new ones through to the IP and the T-Valve.

While you’re back there looking at the FFM lines, check the return line to the tank as there is a rubber hose that makes the bridge from the hard line in the valley to the hard line that starts over the bell housing. Clamps or hoses there could have failed as well but with the way you described the issue, it may only be a point worth inspecting.

Pictures might be of help too.

IP - FFM fuel lines.jpg

IP Return Line.jpg
 
Can someone please advise - if I take the top of the air intake (just the flat bit and leave the eight 'legs' in place) will that give me enough access to the valley to investigate further?
also, as my turbo was getting bit oily I checked it and it seems to have some play ie the fan inside can me wiggled side to side, is that bad?

thanks
 
You don't need to remove anything. Have you looked with an mechanics inspection mirror and a flashlight yet? Your making it way harder than it needs to be. Please do that first and report back.
Turbo shaft play is a bad thing. I would start looking for a rebuild kit or replacement. Alot of pepole are going ATT and selling the stock turbo. You may find a good deal out there.
 
Thank you all - guys esp Paveltolz for the write up, my plan tomorrow is to remove the oil filter base and see what is going on there,
what type and size of fuel pipes do I need for replacing the all rubber fuel pipes around the engine?

thanks
 
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