Hello everybody

I've always visited this site as a lurker, but never posted till now. I have a 2000 RR P38 4.0 HSE which was converted to LPG by a professional installer when I got the vehicle in 2004. It has a Prins Autogas VSI LPG system which has always functioned well. I get 220 miles from a 80l tank of LPG and this has never varied. It's now done 90000 miles, but has always been maintained regardless of cost and fully serviced by Land rover and subsequently LR specialist independents.

The vehicle has developed a really irritating fault which so far has defied diagnosis by my local landrover specialist and also the people who fitted the LPG. I'm looking for any advice on a good rover v8 specialist, preferably in northern England and who isn't afraid of LPG.

About 9 months ago, the vehicle began to make a metallic chirping noise under load with the throttle depressed and with the tachymeter above 2500 rpm. At first this only occurred under hard acceleration on LPG, but since then, it has got worse and now happens at light throttle opening on LPG (although never at idle or when revving in neutral) and to a slightly lesser extent on petrol although it still occurs readily. Economy (if you can use that word for this engine) hasn't changed at all.

About the same time, I noticed a slow coolant leak, but was used to keeping a close eye on the coolant because I often noticed dried antifreeze around many of the hoses, and assumed it might just be that. Otherwise the engine seemed to be pulling well with no misfires.

I have done the following things:

1) Replacement coil pack. 18 months ago
2) Replacement Megnecor HT Leads 3 months ago
3)Replacement Valley gasket for minor oil leak, 12 months ago
4) Replacement blend motors and Heater O rings, 1 year ago
5) Full service of LPG system including filters 2 months ago
6) Replacement plugs and all other service items as per normal schedule. 90000 mile service 3 months ago
7) Replacement Lambda sensors 2 years ago.
8) Replacement cylinder head gasket 2 months ago.
9) Replacement (L) manifold gasket 2 months ago.
9) New full stainless steel exhaust 2 years ago.

Despite all that, the chirping/tinkling noise, which I assume to be pinking, is worse than ever. The head gasket replacement has stopped the coolant loss and there is no steam from the exhaust or oil in the coolant, which I understand can be caused by a cracked block which is my ultimate fear.The oil is clean and levels are quite stable.

The engine is now pulling much less well, both on petrol and LPG and misfires for a couple of minutes when cold. The LPG guy told me to put up with it or seek advice from a specialist so I'd be grateful if anyone can recommend someone who can diagnose this problem (without ripping me off) and tell me if the engine block is porous or cracked.

As you can see, I'm no auto engineer but love the vehicle and want to keep it in full running order. I always thought 90000 wasn't much for one of these engines!

Thanks for any advice.

Rob

if it is doing it on both petrol and LPG then its not a fueling problem - have you had the engine pressure tested? LPG will eventually cause valve damage on the rover V8
which causes misfires, power loss, compression loss

Have the vehicle crypton tuned, cost you £40 and could save a lot of money.
I wouldn't spend anymore without knowing the problem.

If there's a problem with valves or seats this should show up in the tests, as will any emission problems.
Should also be able to tell you if the dizzy is working correctly.

Crypton tune will show nothing
I would be inclined to start with the basic but suspect a worn cam or follower or a sticking valve due to leaking valve stem seals or a worn rocker arm
But really would need to see and look at it to get a good idea

so a valve problem could be an issue? TBH the cold performance does have a misfire, but that's not noticeable when the engine is warmed up. power is reduced on both fuels, but interestingly under hard acceleration, petrol is worse performance than LPG, but the pinking noise is worse on LPG. I can't work it out...

...do a compression test, just to check.......it was the last thing i did and from now on it will be the first....draper, £24 don't overtighten the rubber seal.....it will tell you if a valvecylinder isn't sealing properly for combustion etc what ever the reason is

A leak-down test is better than a compression test, if yu can do it.

...can you do that at home and how does it work please ta.....

Yu can, but it isn't so easy. Lots of articles on it. Basically yu pressurise a cylinder (from an air line) and see how much leaks out past rings, valves etc over a period of time. The good thing about it is that it doesnt depend on cranking speed or the state of your battery, so yu getca much more repeatable result. It has to be done at TDC tho.

I have had similar noises on another car, but they were related to the alternator.

Chirping is a loose alternator / auxillary belt.

Tinkling (metallic ringing) could be the alternator mount / metal tensioning bar that has sheared/partially broken, that is acting like a tuning fork.

Yes, this has happened to me, not on a Landrover, but took a little while trying to locate the sound.

Water pumps can get noisy. On other cars I get them done every cambelt change, or every 60,000 miles or so. For their cost, leaving them any longer isn't worth the risk and damage if they fail.

Impellers break up and could be the chirping/tinkling sound.

Leaving a failing water pump can lead to other problems where the heat builds up from the water-cooling being compromised.

If you get a failing water pump, if there is a cylinder overheating then pre-ignition/knock might happen and if the knock sensor is working, then the ignition timing will be retarded and power/performance is reduced.

If you don't change the coolant often enough, like every 3 or 4 years, then corrosion of cooling components can give problems.

And if you have had poor cooling, head gasket failure is much more likely to happen.