millwallfc

hi everyone, just bought an old 98 LS400, and after conducting a diy service and fixing a few problems i'm left with two issues that I hope someone can help me with.....


1) Intermittent screechy noise when a/c is off, quietens down to almost nothing when aircon is switched on.

I replaced serpentine belt last week as part of a full service, but its definately noisier now!

I've checked the belt is routed correctly, and to my untrained eye (and after a little jiggle/spin) each pulleys/tensioner seems ok ....

The noise is definitely manifesting from near the A/C pulley, and ive noticed the clutch cover on it sort of "jogs/jerks" round intermittently in synch with the noise with the aircon off. When I turn A/C on the clutch cover spins with the pulley and noise is vastly reduced.

My intuition says my problem is with the belt tension (which may or may not be caused by a pulley issue) rather than the A/C clutch/bearing/pulley ... Can anyone point me in the right direction of what to test/try in order to pinpoint cause ?...

2) Ticking from rear of engine - now i read a LOT of info on ticking UFC engines, and to be honest its fried my head! - valve clearences/injectors/egr pipe etc etc etc!

Mine ticks loud enough so you can hear it with hood shut. The ticking seems to eminate from the rear of engine cover, and seems to be constant in tone and volume regardless of whether idling, high revs, cold or hot...

I put some injector cleaner through but made no difference - I mentioned it to my local mechanic, and he told me not to worry about the ticking injectors, reckons they always get loud with age and the cleaner they are the louder they'll be.

Anything for me to check before I try and ignore the ticking?!!


sorry for asking questions that have probably been asked many times before - ive searched the archives and read lots of different opinions/advice etc and being only moderately competent mechanically i'm nervous of trying to fix without being confident of the cause!

all the best,

marty

j2b4o

Sounds like the a/c clutch/pulley are on the way out IMO.
If the ticking is relitively quiet ( almost non existent inside cabin with windows up) than it is likely valves or injectors and it is common and not a real issue for concern.

millwallfc

thanks j2, I guess you figure that the extra load on clutch pulley with a/c on is taking up the slack in worn clutch bearing and hence noise disappears ?

the ticking is relatively quiet, I can JUST hear it inside car with windows shut, but its a lot louder than other similar mileage (150k) 400's that ive listened to. I have a feeling it might be the EGR pipe, as the noise only comes from rear of the engine block. Is there a way to check without a lift ?

LScowboyLS

basically, yes

and as far as tension goes, if you have a new tensioner and the correct new belt, then you can eliminate belt tension, which at that point makes it about 100% chance of being clutch related

likely - exhaust leaks can mimic a valvetrain type of tick

mikes7ke

iTrader: (1)

You could try putting the car on jack stands, and putting soapy water on the egr pipe. Turn the car on. If you see bubbles, it's leaking.

But it's a hard to reach, and see pipe. You might be able to get a mirror and light.

If you want to be sure, you can try taking it off. It's three bolts and two nuts. Two bolts on the flange connecting it to the intake manifold, they can be reached easily with a 1/4" drive ratchet and a 12mm socket. Then there's a bracket about half way through the pipe, holding it to the back of the engine block. This one is hard to reach. But same thing, a 1/4" ratchet and 12mm socket will do the trick if you can snake your arm in there. Some people have lowered the transmission just a little to reach this, and removing the right catalytic converter will also make it less of a chore. And then the two nuts hold the other flange to the exhaust manifold. I used some liquid wrench and I might have even got a 3/8" drive ratchet barely in there, but I have high flow cats, which have more clearance without removing. If it has holes, you can send it out for welding. Other members have said they had theirs repaired for low costs.

millwallfc

thanks for the pointers, i'll brave the snow tomorrow and get it up on stands to check.

will report back!

Lavrishevo

iTrader: (1)

98 - 2000 models do not have EGR's. Correct me if I am wrong but PD and I have already been through this. I don't have one on my 99.

Still worth looking for exhaust leaks.

millwallfc

that would tie up with me not being able to find any reference to EGR in the workshop manual !

so only pre-98 400's had EGR then?

back to square one!

maybe its just the very rear set of injectors then? the ticking does not change tone or volume with revs though, and sounds like its eminating from dead centre of rear of block - just in front of firewall somewhere and top end rather than bottom...

PureDrifter

iTrader: (10)

'98-00 do not have EGR systems.

It's probably just valvelash tick, use a mech's stethoscope and see if it is coming from anywhere BUT the two valvecovers.

millwallfc

will do, thanks for your patience and help.

i'll let you know !