Rapping, tapping noice under load

[Jonny Boaterboy]

I have a strange noice coming from my 3.9 V8 when you put some load on the engine i.e. accelerate or tow a trailer, there is a noise that sounds like a tapping noise which is increased with the load and not there at all on tick over. My first guess would be that it was the tappets, but I belive they self adjust so should not tap

Does any ony know what it could be and if I need to worry about it! The engine has done 150000 but it is good order

Thanks jonny 

[Guardian.]

mine was the liner moving up and down a cracked block! a recon one from v8 developments! and now have a tapping one from them, they couldnt build a frigin lego wall i dont think let alone rebuild engines.

[hairyasswelder]

Mine was doing that and it was an exhaust manifold gasket that had gone  :?
Took bloody weeks to find it  :twisted:

[Jonny Boaterboy]

Well I hope it is't the liners! I thought liners were only on the 4.2? Hey, Guardian was there no black exhaust marks where it was leaking on the manifold? Now you mention it it does sound like that could be it..... ummmm maybe I just want it to be that! will have a look tommorow. I'm changing the timeing chain this week so just wanted to make sure that nothing major was about to give up  :pale:

[ben_haynes]

i am with hairyasswelder mine had been blowing from the day i fitted the manifolds and it had no black soot marks round the manifoldfitted and tightened the bolts and it has now gone

[Guardian.]

THEYVE ALL GOt liners mate, and when they decideto move about it aint good.
hopefully its your exhaust manifold, as mine did that when it had a new system fitted , apparently they are hard to get gas tight on the v8's, but after another go they shut it up.

[Jonny Boaterboy]

Arrr you see gardian sometime you are best keeping you mouth shut to aviod looking like a spanner :oops: I knew they all had liners really! will have a look at the manifold tommorow!

Thanks all

[hairyasswelder]

was there no black exhaust marks where it was leaking on the manifold?

Not with LPG  ;)

THEYVE ALL GOt liners mate, and when they decideto move about it aint good.

Thats why I argue that the 3.5 is the better engine  ;) rare the liners slip on the 3.5 but it is 10 horses or so behind the 3.9.

[Range Rover Blues]

You can get a few of those horses back by fitting a 3.9 cam to a 3.5 anyway.

One fo the reasons (people think) the 4.2 is more likely to suffer a cracked block is that it runs lean, to try and make it economical

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=320219232557&_trksid=p2759.l1259

15-18mpg, hmmmm that's a bit optimistic :?

Anyhoo, I'd go with the exhaust manifold leaking, they are a PITA TBH, I fitted a sports syetm because I got sick of putting a new downpippe gasket on my LSE every month.

The back bolts are very hard to get to on the cylinder head/gasket joint and often work themsleves loose.  Earlier cars had lock-washers on these joints but they rarely get replaced becasue the tabs are impossible to reach once the engine is in the car. 

Later cars have spring washers, well I ask you :roll: spring washers, in an environment hot enough to re-temper steel? they are really going to last aren't they

So they come loose, especially when you drive hard.  My LSE was blowing a gasket every time I towed with it.  I binned the cats too as I think they were blocked, it use less fuel now anyway :D

You might also find that the gasket surface omn the manifold has rusted away making the gasket weaker, this seems to happen worst on the back of the head too :doh:  That's one reason a good pair of manifolds fetch decent money.

[Jonny Boaterboy]

ok so it sounds like I need to reseal the manifolds..... I assume you will need to get a new gasket set using genuine Landrover as they will seal properly...... or am I just hoping! Can you not put a smear of gum gum exhaust sealing paste to make a perfect seal? I will also replace all the nuts with stainless items.

The whole exhaust is getting tired now should I be thinking about replacing it all in one? I would like to get a stainless sports system (because its cheaper than a genuine) complete with manifolds cats and the holes for the lambard sensors has anyone got a second hand one for sale?  [-o<

[Range Rover Blues]

Keep watching E-Bay, both mine came from there, besides you'll find all the double S dealers are the same price, not by coincidence

Otherwise hunt out your local powerflow dealer, ours is pretty useless but I think it was 'lord of the strings' had a really nice system built by the one in Lincs.

Otherwise, well I end up taking the manifold right off, cleaning it up (get the faces flat) and often applying either exhaust assembly paste or similar along with a new downpipe gasket to that joint face (nothing too thick), plus a new gasket set to the head/manifold face.

I've tried the standard sort, composite aluminium and asbestos substitute, I've tried the ones form Rimmer's that look like linoleum too, they would be good except they lined up so badly that they burned through (my heads and manifolds had been ported so less sealing surface) so now I stick with the later OEM style ones, sometimes called twin port gaskets as you need 2 per head.  They are laminated alumium or something, 3 layers of metal and I have found them 100% the best, so much so I havn't touched them in about a year on either car :D

You'll almost certainly have grief with the 3 bolts in the downpipe flange too, I pull them out and fit an M8 bolt in their place.  NB, the bolts for the head are NOT metric, though an M8 will fit and if the thread is trashed an M8 will find a bit of purchase.

I also find it good practice to use studs on the head rather than bolts, the aluminium thread is far less likely to fail is the stud is not spinning in the head when you torque it up ;)

That said I fitted the sports sytem to the LSE with new bolts and lock washers rather than spring washers, if you buy one you'll find it a total PITA to get to some of the bolts, you only want to do that once.