Freelander 1 Td4's High-Press pump with escaping air noise?

When I switch on my FL1’s ignition the low pressure fuel pump (located in the rear R/H wheel arch) operates. It’s a new pump, as is the filter and it all sounds good.

However, as it pumps, there is the sound of escaping air in the region of the High-Pressure Pump under the bonnet. The air sound stops when the low-press pump stops – eventually.

Can anyone comment on this? Is it normal?

And, might someone try the same to see if they too have the sound of escaping air?

Other than that the car runs fine. It’s just weird to hear it.
There's no sign of fuel leakage or anything unusual.

If you mean an hissing sound it is quite normal I have yet to hear of a FL or in fact a R40 with the same engine M47 not make that sound, someone else may differ ?

Thanks, Arctic. I tend to sleep on problems, such as this, so your answer helps. Zzzzzz
I woke this morning and went straight into my garage, having taken on board what you suggest. I wrote a report, which follows as a reply.

Yes the high pitch sloshing is quite normal. I think it is pump churning fuel around.

andyfreelandy said:

Yes the high pitch sloshing is quite normal. I think it is pump churning fuel around.

Click to expand...

Hi Andy, and thanks for that reply. There isn't actually a sloshing noise, or any kind of noise associated with liquid in motion. It's the sound of air pressure being released. Now, I've just finished investigating the noise and its source. Having removed both air-inlet covers for access, I determined the air sound is within the frontal fuel pipe on the high pressure pump (rubber hose clamped to steel pipe), where by wrapping fingers around it reduced the noise. I'm now guessing the fuel is pushing air through that pipe as it's pumped. I'm open to the thoughys of others on this.

I think you should be checking the fuel lines not just those around the pump to see where air could be getting drawn in to the system, and possibly look at bleeding the air out, if there is any in. I would suspect that maybe it is an artifact of when your low pressure pump and the filter was changed, though. Although, as it runs fine, I wouldn't spend too much time on it.

Thanks, Paul. I'm considering everything & anything that might cause this strange occurence. And although it doesn't affect the running & performance, I've just bought a 2nd hand High-Press pump (from Latvia) and a seal kit to suit. I will refurbish this pump and replace the existing one. My belief is, what might seem strange can turn round and bite. I need my car to be 100% and try to keep it as such. Regardless of cost and hours. I enjoy a challenge. And by god, my Freelander 1 has kept me busy.

A hissing sound from the HP pump is quite normal. It's the sound of the fuel being pumped through the HP pump body, before it's returned to the tank. The fuel is moving very fast at good pressure, so it makes a noise as it surges through the pump.

Thanks Nodge. That's exactly what I'm getting. Problem, or what I thought was, solved. I'll still refurbish the pump and keep it in reserve, along with a host of other parts. When I travel I carry a full tool kit and spares pack-up. Thanks again.

Further to my question about air noise, I inspected the water/sediment trap this morning, paying particular attention to the possibility it might be allowing air to enter the system.
It was.

Both connections rotated easily with lots of play. I removed the unit from the car and dismantled it. Both connector seals (x3 each, yellow/red/black) were badly worn. The grey-coloured connector holders were brittle too.

The design of the trap had both pipe ends just inside the cap, where any ingress of air would be easily drawn into the fuel supply line, as was mine.
And the Td4 system automatically bleeds any air from the fuel pipeline, hence the continuous noise I have heard.

I had no rubber washers of the size required so have hot-plumbed (a new but relevant expression perhaps?) the tank supply line to the fuel pipe immediately before the low pressure pump.

It worked. Following a lengthy run the car has no hissing as before.

I will now get the parts I need to either recover the water/sediment trap or replace it. It’ll be a new one if I do.

I’m aware there is a danger of introducing debris and moisture into the fuel system, but on inspection of the trap, once removed, it was spotless. Fingers crossed.

I hope this may be of interest to others.

Interesting information. The pre 2003 TD4 didn't have such a trap but used 2 LP pumps, one in tank and one in engine bay. Whether a trap is necessary and why it was added is a good question.

andyfreelandy said:

Interesting information. The pre 2003 TD4 didn't have such a trap but used 2 LP pumps, one in tank and one in engine bay. Whether a trap is necessary and why it was added is a good question.

Click to expand...

I both understand and agree with what you say. However, it's always good to have a filter... of sorts.
And, I have just ordered the following,
Universal Diesel Inline Fuel Filter LARGE Car Part Fit 8 mm Pipes On Angle
https://www.ebay.co.uk/itm/Universal-Diesel-Inline-Fuel-Filter-LARGE-Car-Part-Fit-8-mm-Pipes-On-Angle/264629492246?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

It will prevent any debris getting through, moisture too perhaps. And it has to be better than the rubbish piece of plastic kit that Land Rover produced and fitted!
What I saw, once dismantled, was a piece of crap. Totally OTT.
I'll be fitting the filter when it arrives, using the appropriate tubing & clips. Very simple and cheap. And there's not much chance of air being drawn in either.

Will you leave the standard in line filter in circuit? Will the new item act as a separator for moisture?

andyfreelandy said:

Will you leave the standard in line filter in circuit? Will the new item act as a separator for moisture?

Click to expand...

No. I've written it off as a useless piece of junk, which is exactly what it is.
I have confidence in most bits of kit, but the lump of air-leaking plastic I have just discarded has no meaning or use whatsoever to me or my car.