j_rov · Dec 12, 2009

Hi All

My 300TDi disco has developed a power problem. (lack of it). The engine revs all the way thru the range but power on the road is definitely down on what it was - not pulling in any gear up hills.

Also, I used to get black smoke when gunning it, but dont get any now.

So, tried the following

Air, oil & diesel filter change
Removed, checked, cleaned and refitted all air hoses
Removed inlet manifold & cleaned with parrafin
Removed intercooler & cleaned as above
Refitted both when totally dry (SWMBO hair dryer!)
Refitted manifold with new gasket as I thought i had a small exhaust leak
Cut off air-con belt today as the compressor bearings sounded dead - noise stopped but no more power still.

I've not touched the sedimenter as the plastic plug feels like it will snap off

I've not modified anything else since it felt "normal".

Cant tell if fuel consumption is affected as it doesnt do enough consistant road miles.

Only thing i did do was some fairly deep wading that wet my air filter & caused a bit of white smoke, but it seemed OK straight afterwards.

Any ideas guys... i guess i have to take the plunge with the sedimenter at some point (what happens if i do snap the drain plug?)

Your expertise and experienced advice much appreciated.

rollin danny · Dec 12, 2009

You need to take the sedimentor off and clean it out. The plastic plugs are a waste of time and they do snap off ! Dont touch it .The bolt to remove the sedimentor is on top of it.Put a bag over it first to avoid being covered in fuel when it comes apart.

j_rov · Dec 12, 2009

rollin danny said:
You need to take the sedimentor off and clean it out. The plastic plugs are a waste of time and they do snap off ! Dont touch it .The bolt to remove the sedimentor is on top of it.Put a bag over it first to avoid being covered in fuel when it comes apart.

Will it be full of crap or water? If it is full of crap, should i get excited that i found the problem!!!!!!!

When removing, am I likely to need any parts for refitting? I prefer to get it all ready first...

Also, does the fuel flow under pressure or gravity thru the sedimenter - dont want to end up draining 80L diesel over the drive!

nicedayforit · Dec 12, 2009

11mm ring spanner for the nut on the top to remove the bowl.
It may be full of water and crud and possibly some diesel. Just clean out what you find.
Removing the bowl will not let any fuel drain from the tank.
You should get a new set of rubber seals for it before you start, although I've had mine off twice to date and not replaced the seals - no leaks yet.
When the bowl is off It's worth replacing the plastic drain with a stainless steel bolt, from memory it's M8 (but I could be wrong) at least then in the future you have a means of draining the thing without breaking it.

rollin danny · Dec 12, 2009

Sometimes they are full of bacterial jelly a bit like man cheese

j_rov · Dec 13, 2009

Thanks chaps, will have a go tomorrow.

j_rov · Dec 14, 2009

I've now cleaned out the sedimenter (and got covered in doozil!). It wasnt very dirty, few specs of grid and a layer of slimey stuff. Was a bit of goop in the bottom, maybe 5mm or less...

While off, i blasted the lines with the air hose (and got soaked again!). Changed fuel filter again.

Seems marginally more responsive but still lacking in pulling power up hills.....

Maybe I'll do the fuel pump tweak, although I'd like to find the problem rather than just add more diesel.....

Maybe try a redex shot also...

any more ideas?

Dewin · Dec 14, 2009

j_rov said:
Only thing i did do was some fairly deep wading

Have you checked the brakes after wading, and is the turbo kicking in ok?

300's are gutless if the turbo or hose's are knackered, even a small tear in the turbo hose's will make a big difference to power.

nicedayforit · Dec 14, 2009

Could be pulling air into the fuel line.
Usual suspect are the two elbows on the top of the sender unit on the fuel tank.
The elbows corrode and perforate allowing air to be sucked in.
Access via round panel in boot floor.

j_rov · Dec 14, 2009

Dewin said:
Have you checked the brakes after wading, and is the turbo kicking in ok?

300's are gutless if the turbo or hose's are knackered, even a small tear in the turbo hose's will make a big difference to power.

brakes seem to be ok... wheels spin freely.

i can hear the turbo whistle, but it's not that loud... should it be? Hoses are deffo OK...

j_rov · Dec 14, 2009

nicedayforit said:
Could be pulling air into the fuel line.
Usual suspect are the two elbows on the top of the sender unit on the fuel tank.
The elbows corrode and perforate allowing air to be sucked in.
Access via round panel in boot floor.

Thanks, I'll have a look at that at the weekend. Gonna do a load of road miles this week to see if it's just requiring a good run...

Dewin · Dec 14, 2009

j_rov said:
brakes seem to be ok... wheels spin freely.

i can hear the turbo whistle, but it's not that loud... should it be? Hoses are deffo OK...

I think that's down to each individual Disco, our 1st was just a quiet whistle, current Disco sounds more like a banshee! ... make's pedestrian's look around when you boot it

(but I am a bit heavy footed when accelerating)

Did you check the hose's internally? as they tend to fall apart so that when the turbo kicks in the hose's inner layer closes on itself restricting air flow.

j_rov · Dec 14, 2009

Dewin said:
I think that's down to each individual Disco, our 1st was just a quiet whistle, current Disco sounds more like a banshee! ... make's pedestrian's look around when you boot it (but I am a bit heavy footed when accelerating)

Did you check the hose's internally? as they tend to fall apart so that when the turbo kicks in the hose's inner layer closes on itself restricting air flow.

I'm gonna check the hoses again just to make sure - is it more likely the "ribbed" one from the airbox or the one from the intercooler?

Dewin · Dec 14, 2009

j_rov said:
I'm gonna check the hoses again just to make sure - is it more likely the "ribbed" one from the airbox or the one from the intercooler?

The hose's connected to the intercooler are probably the more likely to have rotted, 3 hose's in all to check ... intake, intercooler bottom & intercooler top.

The "ribbed" air box hose is pretty sturdy but might well be damaged, have a search for some turbo thread's as they will explain much better than I ever could for thing's to check over. Have a double check on your exhaust manifold gasket, as the new gasket could well have a leak (our's lost power when the new gasket did not seal correctly).

rollin danny · Dec 14, 2009

Have you checked the boost pipe that runs from turbo to the fuel pump.They can split or even melt if they touch the hot manifold.If its faulty you will not get any boost fueling, resulting in lack of power.

j_rov · Dec 15, 2009

rollin danny said:
Have you checked the boost pipe that runs from turbo to the fuel pump.They can split or even melt if they touch the hot manifold.If its faulty you will not get any boost fueling, resulting in lack of power.

This sounds likely, is it the thin plastic/rubber pipe about 3mm diameter?

rollin danny · Dec 15, 2009

Thats the one. Round the back of the engine to the fuel pump. Sometimes they get full of oil that restricts the air pressure to the pump.

tapper · Jan 30, 2010

Have you fixed this problem as it sounds just like mine 300 tdi

pete5570 · Jan 30, 2010

Might be worth taking the intercooler off and flushing it with paraffin or something. It made a real difference to mine.

tapper · Jan 30, 2010

Thanks Pete have done this already
Also run engine with suction hoses removed incase they collasped ,no change,
Also disconnected the plenum chamber inlet hose and rev'd extra air flow achieved
Boost pipe to injector also checked and OK

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