Valve Clearances?

[BrianH]

Hi everyone,

Please excuse double post - I posted this question in response to a valve clearances article but I'm thinking maybe I shouldn't post questions there, so I'm going to post here instead.

I've started this job today but I left it a little late in the afternoon and it's getting dark (and the bulb went on my floodlamp) so all I've managed to do is get as far as removing the rocker cover and taking a look inside.

The reason I'm checking the valve clearances is because my Discovery has suddenly begun to make a noticeable tapping sound. I say "suddenly", I've actually thought a couple of times that she sounds more "tappy" than she used to, but it was marginal. Now it's quite clear that she's tapping, and the noise is more noticeable at low revs. Is this the kind of thing you would associate with valve clearances? If so, are there any other symptoms I should be able to notice?

The fact that the valve clearances could be out makes sense to me because the head was replaced about a 12 month ago so I suppose the valves could have bedded in a little more and hence the clearances would now need doing again. Does that sound plausible or am I talking giberish?

Also, please see attachment. I have drawn a white arrow on Pete's drawing to point to a component that caused me some confusion when I took the Rocker cover off. I'm not sure what this part is for (tension springs?) but one of them was swivelled around to the side. I moved it back easily enough, but should this part be able to move about like that? And could it cause any problems?

Advice is appreciated, and I'll check the clearances tomorrow in any case.

Thanks, and Merry Christmas!

Brian

[TEMPL4R]

You see how the rockers have a slight bias to one side? Those spring clips are to keep the rockers against the rocker shaft supports and on top of the valves. As long as they aren't broken, twist them to the top.

Tapping could either be the tappets or the brake exhauster ( vacuum pump) on the drivers side of the engine. Pump the brakes while the engine is stopped, then start up, if the noise is heavy then reduces, it's the vacuum pump.

Chris

[BrianH]

Thanks for that Chris. I've got the Rocker cover off now so I'm going to check the clearances tomorrow and adjust if necessary. If she still taps after that I'll try your idea.

Thanks again for the info.

Brian

[bilge rat]

another thing to check when you do the tappets, iff you look on top of the valve, there is like a little cap. these are prone to wearing and eventualy the valve will punch a hole through them this gives the same sympyom as a loose tappet so have a close look. there only pennies from l/r. good luck .alan.....

[BrianH]

She's done over 200,000 miles so yeah that's definitely a good idea thanks for that, I'll have a look tomorrow.

Brian

[CCKW353A1]

The Bosch injectors can also make tapping noises.

[BrianH]

Ok I've taken a look and there is a definite problem with the clearances. Number 2 valve is loose (very loose) and the cap has taken visible damage. Can anyone advise regarding this? My immediate thought is to go out and buy a new cap, fit it, and then adjust the clearance again. Is this what I should do, or could there be other problems I should consider?

Regarding the other valves, I checked them all and apart from number 2 which was very loose, all the others seemed to be too tight because I couldn't get my feeler gauge in there. It would go in part way, but then become stuck. I followed the list given in the manual (7 compressed check 2 etc) but with the exception of no.2 they all seemed to be tight.
What are the consequences of a valve clearance being set too tight? Should I go around and adjust all of these as well?

Advice appreciated. I won't be able to do anything now until Bearmach opens after Christmas but any advice the more experienced members can pass on would be very welcome. I'm not going to run the Land Rover anymore now until I can get the clearances sorted out. Out of interest though, what would have happened if I'd ignored the tapping noise until the cap had completely disintegrated?

CCKW353A1: Thanks for your reply I've heard of that. Mine are brand new injectors, and infact that's how I got into this mess in the first place. One of the old injectors refused to come out and disintegrated inside the head. That's why I had to replace my head, and I guess I should have checked the clearances before now to be honest.

Brian

[bilge rat]

get a complete set, there only cheap then adjust the hole lot, theres nothing else to do or be worried about, it is a known fault. id get gen ones from land rover for what its worth think there 80 pence each or something. mine did 1 was no1 cyl .trouble is its difficult to tell how worn the others are. alan.....

[TEMPL4R]

If they are too tight, they might not be closing fully and burn the back of the valve and the seat, you must reset them.

If the cap comes out, the rocker can bounce and the pushrod come out. The caps generally sit in the head if they fall out. I've never had one jam in a spring or fall down a push rod tube, but I have found the problem quickly, when the customer gets it to us or the driver notices the tapping noise.

If the pushrod comes out you get a misfire, if it's on an exhaust valve, a chuffing back up the intake. It draws air in, fires, but can't exhaust, so chuffs back when the inlet valve opens.

Chris

[BrianH]

Ok thanks. The one thing that concerns me is that all the others seem tight. I don't think I'm doing anything wrong but because I haven't had any experience with this it niggles at me (am I checking it right etc).

I'll buy myself 8 valve caps (is that what they're called?) and adjust the whole lot as soon as I can. I'll see what she sounds like after that!!!

One thing that did occur to me while I was doing this; imagine doing a 24 Valve!!! Nightmare!!!

Brian

[TEMPL4R]

The vast majority on modern engines have hydraulic tappets.

I did the Volvo Penta engines on the Bosses boat, 24 valves, 4 per cylinder, but 2 push rods per cylinder ( work that one out ;))

You are using the Rule of 9 ( Rule of 13 on a six cylinder in line engine), just make sure the valve is fully down, then set the corresponding valve. You're better being a bit wide than tight. Turn the screw until it just nips the feeler guage, turn back a fraction until the feeler slides nicely, keep hold of the screwdriver whilst you tighten the nut, then check it hasn't tightened up on the feeler.

Chris

[CCKW353A1]

24 valves, 4 per cylinder, but 2 push rods per cylinder ( work that one out ;))
Nothing new with that, where i used to work they built bigish diesels that had a main rocker that contacted the middle of another rocker that bore on each valve of the valve pairs. Oh the cylinder liners were about 7' long and 24" bore. V12 configuration, twin turbo chargers & i think intercooled running at 500rpm, a ladder and walkway each side of the engine to get to the cylinder heads.

[TEMPL4R]

Sounds like a similar set up CC, set the cross arm up, then the tappet. The Foden 2 stroke just used a Y shaped rocker, dead simple.

What make were your engines?

The largest I have done any work on were Sultzer Loco engines.

Chris

[BrianH]

So... I managed to get myself 8 new "caps". I got home from work a little earlier, got myself dressed for the occsaion, setup a flood lamp to illuminate the engine bay, got some steps to make it easier to get in there, got all my tools out and ready, and JUST as I start the job...

Rain.

It's been dry all bloody day, and now it decides it wants to rain. A little shower? No way - it's here to stay by the look of it. Fantastic that is.

So anyway I managed to do the problem valve before the rain got heavy. The damaged cap has been replaced and I've set the clearance right, but the old cap didn't have a top to it anymore!!! It'd been "cut out" completely. That leads to the obvious question... where has the debris gone???

And that's my final question really. Should I be concerned with that? Not a lot I can do about it in any case I guess.

I'll be doing the rest as soon as the rain clears. Thanks for the help all.

Brian

[TEMPL4R]

This is where a magnetic drain plug comes into it's own.

If it has broken into small bits, it can work its way into the sump or into the valve springs or cam follwers, where it will lay.

I wouldn't worry too much to be honest. It's been gone for a while and would have done the damage by now. If it's small enough to get through the strainer in the pickup, it's small enough to get through the pump and into the filter.

Chris

[bilge rat]

never found mine think it wor to nothing, as chris said about the magnet on the drain bung . iff your bothered do an oil and filter change .although i didnt. alan.....

[d1scv]

Not yet seen any mention of if engine should be hot or cold.

[BrianH]

I've got some very potent magnets kicking around in my drawer. Perhaps I could attach one to my drain plug (thereby magnetising the plug)and see if it picks up anything. I somehow doubt it, but I think I'll try it just out of interest!

I'm due for an oil change in about 1000 miles anyway. I do it every 6000 so she stays pretty clean in fairness.

Brian

[TEMPL4R]

Not yet seen any mention of if engine should be hot or cold.
Cold .20mm or 8 thou

Chris

[BrianH]

How would you do it hot anyway? You'd never keep it at a constant temperature.

I managed to finish mine tonight during a break in the rain. She's sounding MUCH better :)

Brian

[d1scv]

How would you do it hot anyway? You'd never keep it at a constant temperature.

I managed to finish mine tonight during a break in the rain. She's sounding MUCH better :)

Brian
Going back a few years, was done with engine running. Yes, a fair few years, and yes you got covered in oil. It was very accurate but top quality feelers were needed.