discover td5 air in fuel problem

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cummins90

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discovery 2 td5 air in fuel problem
hi all, problem with a td5 discovery. pump started squealing with air bubbles in the system, i immediately changed injector copper washers to no avail, i have now changed them 3 times in an attempt to stop this......
ran clear pipe on the return and when engine is cold there is no bubbles and the pump runs quietly until it reaches running temperature and the bubbles start rushing through and pump cavitates when restarted.....changed the pump aswell. in a desperate bid to fix it i fitted another engine,since i thought there was a crack somewhere in between rail gallery and cylinder. the problem still exists! no problem at all until engine temperature reaches half way on the gauge!
any help will be highly appreciated!
thanks
(all genuine parts fitted)
 
the only other things you have that can cause problems are the fuel filter and it's housing, mine had a tiny crack that drew air into the pump hp suction. The fuel pressure regulator that normally leaks onto the gear box and the fuel cooler.

My guess would be it's the pump drawing air somehow. Check the fuel filter only has one of ring in it. In fact for the price change it and inspect the housing for cracks or damage. the fuel cooler is done by the water cooling system so maybe it also heats the fuel once it gets to temp and causes something (ie a crack to open up)
have you tried fitting a clear hose before the fpr to see if the bubbles are before the engine or removing the fuel hose to the fpr and running it into a clear container or bottle to see if it still has bubbles in it?
 
I didnt think the filter and its housing and the pipes can draw in air while pump is running as all of it is positive pressure, the only place it could draw is from the base of the pump, but tank is full to the top and its had a new pump which hasnt made a difference, surely if a crack was somwhere on the pipes and filter unit there would be a damp patch there somewhere... But i might be wrong, tried everything else. Only other thing it could be is that the donor engine from the scrappy has got a copper washer problem which would be a coincidence, but when i got it the the rocker cover gasket looked as if its been pulled off and back on a dozen times all squeezed a shredded..... I dont know.... heres the thing it only releases bubbles when engine hot and revved or driven if left to idle it comes back to normal, it has the symptoms of copper washer written all over it...
 
cummins90 said:
I didnt think the filter and its housing and the pipes can draw in air while pump is running as all of it is positive pressure, the only place it could draw is from the base of the pump, but tank is full to the top and its had a new pump which hasnt made a difference, surely if a crack was somwhere on the pipes and filter unit there would be a damp patch there somewhere... But i might be wrong, tried everything else. Only other thing it could be is that the donor engine from the scrappy has got a copper washer problem which would be a coincidence, but when i got it the the rocker cover gasket looked as if its been pulled off and back on a dozen times all squeezed a shredded..... I dont know.... heres the thing it only releases bubbles when engine hot and revved or driven if left to idle it comes back to normal, it has the symptoms of copper washer written all over it...
Click to expand...

That sounds very much like the washers leaking when the pressure gets high, could be they don't seat as they should, I clean my injectors carefully with a wire brush and then wash the tips with brake cleaner, cleaning the seats is difficult but I have often wondered about using a pice of dowel same size as the washer and pushing it down the opening then rotating it on the washer seat, then clean with cloth.
This year I took out my filter housing and cleaned it thoroughly then put new copper washers on the hose tails which screw into it, then fit a new filter, didn't take long.
Also the pressure regulator on the head is a suspect you can get a kit to overhaul quite cheap, but watch the little mesh filter which sits behind it, it falls out and vanishes.
 
i had a chat with the guy that welds these heads when they crack and he said if this happens even with new copper washers installed, the injector clamp bolts can stretch with heat causing blowby passing the copper washers, the clamp down bolts should be changed as "they turn to toffee". has anybody had experience of this where the problem is solved by changing the bolts. personally i cant understand this as the bolts are of 10.9 hardness and not the stretch type.........
 
It's pretty standard to apply a torque of approx 70% of the bolt yield strength which should allow the bolts to return to normal but remember the washers should be soft and compress it's been mentioned on this forum to go back and re torque them after a few hundred miles.
 
What do you mean by 70% yield strength, the norm is around 32nm dont think they will take much more as they are known to shear same goes for the rocker bolts... Do you suggest they should be given a bit more?
 
Last edited:
cummins90 said:
What do you mean by 70% yield strength, the norm is around 32nm dont think they will take much more as they are known to shear same goes for the rocker bolts... Do you suggest they should be given a bit more?
Click to expand...

No don't tighten them more, what I'm saying is by using the correct torque the bolts should not be pulled beyond their elastic limit and should be OK to re use. When I say re torque what I mean is after they have been on for a while just re check them by setting the wrench to 32 nm make sure they are all still correct and that the washers have not compressed.
 
cummins90 said:
Whate do you mean by make sure washers arent compressed? They are compressed to make a seal.
Cheers
Click to expand...
Of course the washes compress initially, they are annealed copper and designed to compress slightly to seal, then when you run the engine its possible they bed down more then the bolt will loose a little tension, and the pressure on the washers would be slightly less.
That's why its a good idea just to check that they still at the correct torque.
 
I have done dozens of these injector Seals over the years with absolutely no problems afterwards until this one, it is no way rocket science, just make sure everything is spotless, i have machined a rod to the size of the bore and all i do is glue a piece of fine scotch pad on the end and trim to shape, works a treat like lapping a valve to take carbon off without damaging the seat...
 
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