Dear all

I have two noises and another separate quirk that I am trying to identify in my Discovery 2 TD5 (1999) with an auto box;

1 - When moving off from the stationary, there is a distinct "hiss" which is related to the throttle and throttle use. If moving off from stationary, it will last about 1-2 seconds and then disappear. It won't come back unless I idle and lose speed, and then use the throttle again - when it will briefly (less than a second) re-appear, or if I go back to a full stop and start off again. Should it do this? My 300 Tdi never made this turbo hiss type noise!

2 - When moving at low speed and higher torque, i.e. moving up a hill slowly, there is a rattle coming from underneath the car. It only happens between 1750 & 2500 revs, and only at low speeds. It does happen in the same rev range on the flat, but is less noisy. It dissipates largely when the car is very warm, and has been running for 30 minutes or longer. Any ideas?

3 - Just a ****le - she can sometimes be slow to change up properly to 4th gear. She should move upto 4th at about 55mph, and will should drop down to about 2,000 revs. However, whilst she is cold, she will change up, but the revs only drop down to just below 3,000 revs. It can take anything between 10 - 25 minutes before she is warm enough to fully drop down in revs at 55-60mph. Any ideas?

Thanks so much in advance to anyone kind enough to reply.

Richard

 

My first impression is that items 1 & 3 might be related to vacuum leak. There should be some vacuum lines that go from the intake manifold down to the modulator on the auto box. Maybe a leak with those somewhere?

Item 2 may be a loose heat shield on the exhaust somewhere? Hard to say without expriencing it?

 

What year is your truck? I am assuming you are talking about a gas engine, if so, the rattle may be coming from your cats. Might want to crawl under the truck and hit them with a soft hammer or your hand, when the engine is cold, nd see if they rattle. If they are noisy, they will need to be replaced as well as the engine needs to be inspected to determine what caused the cats to fail.
If you are driving a D2, your tranny is regulated by electronic controls and will not sit into 4th gear or lock up till the engine has warmed up, so what you are describing could be very normal. By the way, how long since the tranny fluid was changed?

 

Sounds like you need to change your oil and make sure it is the right weight. If I understand right, your diesel is clacking hard under load (going up hills)? Check your tranny fluid too. If it isn't shifting right, look there first.

Tha hissing might be from a loose connection on you intake. The tube from your turbo to your intake might have a small leak.

 

Thank you kindly for your reply - I will start to investigate what you have suggested immediately!

Thanks for your time - much appreciated.

 

So, it is still not clear to me, do you have a diesel or gas engine?

 

My fault - I should have stated that she is a TD5 Diesel auto. Without knowing as much as I should, I think I am right in saying that diesels don't have the cats in the exhaust? Does that mean that your suggestion above was for a petrol?

About the lock-up, you are spot on, but I was driving her today, and she took ages (30+ mins) before she would lock-up properly, and drop down into 4th properly. The other thing that I have noticed, is that if I were to start a journey, and get onto motorway fairly quickly (under 5 mins), she will not lock-up into 4th properly, as she is still cold. However, even after sitting on the motorway for 20+ mins, and will be pretty warm, I would have to come off the motorway, drop down to normal speed (approx 30mph), and then go back up over 55 to get the lock-up to work. It won't just happen when she is already cruising at 60 mph or over, without going under the normal "change up" speed, which is 55mph on mine. Does this sound wrong?

I don't know when the tranny fluid was last changed. I've only had her a short time, but from what people are suggesting, a transmission filter and fluid change could well resolve this issue (i hope)!

 

Thanks for the reply. When you say change your oil, are you talking about changing the engine oil to resolve the rattling noise? Whilst I am limited in my mechanic knowledge, I am certain that it is not the engine itself that is rattling, but more likely something attached to it, hence it the rattling noise being driven by the speed of the engine when you hear it.

I do appreciate that this is a difficult ask on the fourms, as no-one can hear what I am hearing!!

Thanks for the suggestion on the hissing - intake, I will be under the bonnet to check this, as soon as the wife comes back with it!

 

Take a rubber mallet to your exhaust and see if anything is rattling. My suggestion was for your engine....if you have a bad injector, you can lean out the oil and cause a lot of clacking. It will kill your turbo too. Check your oil just to make sure. If you haven't changed it since you got it, I would change it just to be safe. Just so you know when it was changed last.

 

For those that read this thread - all three problems have been identified and resolved (well sort of!)

1 - Hiss was caused by a leak / crack in the flexi-joint on the old exhaust downpipe. Hiss has gone completely with the new pipe that has just been fitted.

2 - Rattle has been identified as also being the downpipe as I suspected. However, I got a replacement from a salvage specialist, and whislt it cured No. 1 - it still rattles (which you couldn't tell until fitted), therefore still have the torque rattle. At least I know what it is now though.

3 - Completely cured by fitting a new transmission filter kit and new gearbox fluid. It will happily change up to final lock-out at 55mph, when still only a quarter of the way on the temp guage on the dashboard clocks - which is excellent news.

Anyone got a good downpipe for a non-cat TD5?[/align]