1983 XJ6 walkaround idling/revving - YouTube

See if you can hear anything over my cud chewing.

 

If you skip to about 1:12, you can hear what it's doing, but it's not that loud (that's just the sound of the exhaust blowing over the mic).

 

Found this:

If a catalytic converter is clogged severely, it can cause abnormal vehicle exhaust noise, most notably sputtering and popping, due to the erratic flow of the vehicle exhaust flowing around the constricted parts of the catalytic converter.

 

That exhaust does sound very strange, almost like a tapping noise. So your prognosis could be correct; after all the cat box is now over 25 years old, and could be clogged up with engine oil burning products.

 

Sorry, forgot to mention - is the exhaust the original ?

 

It doesn't appear to be--some of the flanges don't seem factory. But it all appears to be very old, nonetheless.

 

amcdonal,

I've just had a listen to your video, and I'd put money on that being a tappet clearance problem. If memory serves me correctly, the Series 3 still used the 'shims' system for adjusting the tappet clearances, and the tolerances were fine. One used a feeler gauge to check the clearance, and a micrometer to measure the thickness of the shim. I can remember hand polishing a slightly over thick shim (they were supplied in various thicknesses and were about 20mm or 3/4 inch in diameter) using emery paper to get the perfect clearance, and to remove a slight hollow or indentation in the shim which would result in just such a noise. It's a job that requires patience & time (and I recommend that if you have the skills that you do it yourself unless you have money to burn). I'm not a betting man, but I'd damned near bet London to a Brick that when you lift the camshaft and the buckets over the tappet shims you will find 'hollows' where the valve stems have worn the shims.

I think that you have two separate 'bugs' to fix here. The exhaust noises are probably not part of the tapping sounds problem, although if the wear on the shims is bad enough it will affect the valve opening times and thus the flow.

Before doing anything else, I'd also suggest a compression test to find out if you do have any leaky valves. Do the 'oil down the hole' trick: variations in compression's caused by worn rings will come up, leaky valves they will stay the same. There is not much point in resetting tappets if you have a valve that needs re-seating. And one is leaking and needs to be re-lapped, there will be others close, so just do the lot. It's a time consuming job, but well worth it in the finish. The change in the performance once done is amazing.

Cheers,

Languid

 

p.s. one 'slick trick' I remember was to turn the shim over so the hollow was under the bucket undersurface and a flat surface was therefore presented to the valve stem. But not if the shim had too much wear, as there is a chance that it will crack under load from the valve stem's pressure if the hollow is too worn.

Languid

 

Thanks for the tip. I think I really need to stop being lazy and get a compression tester and figure out what's going on.

But in the meantime, how hard is it to remove the catalytic converter? Is there only one on the car (under the hood near the exhaust manifold)?

 

I don't know about the catalytic converter, the only one I've ever tried to remove was on a Jeep: I ended up removing the pipe because the clamps had been pulled so tight that the only other option was a gas axe.

Something I did remember re the valve lapping though, was turning the head upside down on the bench, tapping the lapped valves down with my finger, and filling the chambers with turps. You then leave it overnight, and any that are not properly seated will have leaked down by morning. Pernickety, yes, job perfect, you bet!

Ye Gods, I've just recalled something else: leaky valves will give you popping & chuffing noises out the exhaust. The problem may well be one & the same. Sorry 'bout that, its just been so long since I've done or come across anyone doing a valve grind.

cheers,

Languid

 

The catalyst located in the downtube from the manifold is a pre-catalyst to handle excessive emissions when the engine is still warming up. It's placed close to the engine so it heats up quickly.

There is a second, main catalytic converter under the vehicle in the connector pipe, which can be replaced with the pipe or separately by cutting out the old one and welding a new one into place. You can purchase a universal catalyst for less than $100US.

 

Hmmmm, thanks. I did another seafoam treatment. I'm not sure if it's much quieter than after the first seafoam treatment, but I no longer hear the ticking from inside the car unless I have the windows open and I'm next to a retaining wall or something else that reflects sounds. I think it is a normal amount of noise for an engine this age. Hopefully it will get better with driving it since I really don't feel like doing much with the engine!

I think I can live with whatever burbling is coming out of the exhaust for now--the car runs great. Except for the fan clutch which squeals occasionally.