Alfa Romeo Forum banner

41 - 52 of 52 Posts

·
Registered
Joined
·
2,602 Posts
As a very rough test you could pull the spark plug from that cylinder and turn engine over to see if compression escapes, block hole with some tissue or something and see if it pops out. As said it’s a very rough guide to see if it is making any compression or if it’s all being lost through the valve.
I wouldn’t turn it over with the cam though,best to do it either with the crank or jack one front wheel off the ground and put in gear then turn the wheel to rotate engine
 

·
Registered
Joined
·
465 Posts
" I'm just hoping it's the hydraulic that needs to be changed, cause when I turned the engine over I watched each hydraulic coming up properly as the cam passes and goes back down as the cam point presses on its just the 1 hydraulic that isn't coming back up, and as the cam point passed it I managed to fit in my fingers and lift it back up and after a few seconds it goes back down on its own so I think that 1 specific hydraulic is shot, however when I do turn the engine over from the cam everything turns fine and at a certain point you hear the engine makes a sound of releasing compressed air when it hits the correct timing marks so that means there is compression right? "


It is very unlikely that the tappet is the problem. The tappet doesn't move itself, it is pushed down by the cam lobe, and upward by the valve spring. The tappet doesn't resist the cam, that is the valve spring. The valve spring is hidden beneath the tappet, the tappet is interposed between the cam lobe and the tip of the valve stem, the valve stem is firmly attached to the valve spring. The tappet is pushed back upward by the valve spring, not by itself, and not by the internal oil pressure that exists when the engine is running (this pressure is only to eliminate very small running clearances between the cam lobe and the tappet face, not to accomodate what would otherwise be an enourmous gap resulting from the valve sticking partially open).

Keeping in mind that the valve stem is attached to the valve spring;
If the valve stem is bent then as the valve attempts to close, the bent stem jams in the valve guide. This prevents the valve stem from sliding all the way home in the guide, i.e. the valve stops moving before it closes. The valve 'jams' in a partially open position, and is then forced 'unjammed' by the cam lobe as it rotates around again, i.e. the valve can fully open, but cannot fully close. This means that the jammed valve is not pushing the tappet all the way up, so the tappet stops moving before it should. Consequently a gap opens up between the tappet face and the cam lobe face. This gap can be closed manually if the tappet is lifted by hand. To re-iterate, the tappet is most probably fine, the problem (as described) is to do with the valve.

The "sound of releasing compressed air" you've heard may be compressed gas escaping through partially open valve(s), but far more likely it is compressed gas escaping past the piston rings. When manually rotating a crankshaft (which means a very slow rotation, with very slow piston movemenmt) it is not normal to be able to hear gas escaping through a correctly functioning valve, but if the valve is leaking then you may (a big leak, such as might be caused by a bent valve, is unlikely to be audible as the gas will move through too easily, but a smaller leak may concievably 'hiss'). When manually rotating a crankshaft (slowly) it is quite normal to hear compressed gas escaping past the piston rings, i.e. it's not a problem because at much faster operating rpm the gas hasn't enough time to escape significantly (unless there is actually a piston ring problem).

Without a compression tester;
Rotating the crankshaft by hand you should be able to feel compression in each cylinder. This is a very rough measure, but you should be able to tell if one or more cylinders has considerably less compression than the others. If the tappet is freely moving as much as you describe, I would expect you to have zero compression in that cylinder. For every rotation of the crankshaft you should have two compression 'events', for every two rotations you should have four 'events'. If you are rotaing the engine from a cam (not the best idea...), then be aware that the camshafts rotate at only half the crankshaft speed (so two turns on the camshaft equals only one on the crank).

Or,

Remove the four large spark plugs, place the end of a finger over one of the plug orifices, have an assistant briefly crank the engine over (this assumes that you can get the end of your finger onto the plug orifice, I don't know how hard that is on a this particular engine, never tried). You will feel the compression, and you will feel a considerable to significant difference between cylinders.

Regards,
John.
 

·
Registered
Joined
·
2,556 Posts
To check for compression by sound, in one given camshaft rotation (2 crankshaft rotations) there should be 4 separate areas of resistance and sound of escaping gas.
If there is only 3 areas of such then one cylinder has no compression.
If you marked a camshaft pulley, it would aid identifying how many cylinders are still good.
 

·
Registered
Joined
·
2,556 Posts
I just realised John had posted similar which is rather lengthy.
Another reason may be a broken valve spring. Hopefully the valve moves high enough to be kept out of harm's way.
The major issue to that is that the TS has double valve springs.
 

·
Registered
Joined
·
32 Posts
Discussion Starter #45
I just realised John had posted similar which is rather lengthy.
Another reason may be a broken valve spring. Hopefully the valve moves high enough to be kept out of harm's way.
The major issue to that is that the TS has double valve springs.
So let's say it is the valve spring that is broken, what's the easiest way having that changed?

Will I have to remove the cylinder head to change the spring?

Or even if I need to change the valve will that require me removing the head or could I do it with the head still on? I've never done this much of work (changing valves and stem seals and all of that...) before so the most detailed advice would be great guys....
 

·
Registered
Joined
·
2,602 Posts
Yes head off job to change the valve, spring typically yes head off also but there are kits you can get for certain engines that allow stem seals to be changed in situ which requires removing the spring,not sure if it’s possible on these engines though.
 

·
Registered
Joined
·
465 Posts
That you had an issue with the belt tensioner and, "like a metal kind of noise when I crank the car", and how your cranking engine sounds in your video, all strongly suggest that the most likely issue is a bent valve. This is most likely caused by the valve timing slipping off spec because the belt had jumped one or more teeth (or when the tensioner was changed but the belt wasn't correctly re-installed). You need to stop wondering and do a compression check as your next move.

It is very unlikely that a valve spring is broken and causing your problem, this is quite a rare failure (I've never personally seen a broken valve spring in over forty years of messing with cars).

It is possible to change a valve spring without taking the head off (involves threading a quantity of rope through the plug hole, rotating the crank until the rope is compressed and jammed between the piston crown and the valves, then compressing the spring etc...). This can also be done using compressed air to force the valve shut while the collets and springs are removed (etc). However, from what you have asked and said I suspect this is beyond your skill level. I think you need to have the engine looked at by a competent mechanic, as you seem quite out of your depth...

Regards,
John.
 

·
Registered
Joined
·
107 Posts
Aah sorry! Didn’t actually see that bit.😳

Personally, I’d start by checking if the head gasket is OK by pulling the oil pin and checking for signs of coolant fluid in the oil, and then checking for signs of oil in the coolant. Also check the spark plugs for water. As I’m, sure you know, are signs of e.g. water in the oil a good indicator of a broken head gasket. Water in the cylinders might stop the engine from turning on.

As others have already stated: Be sure that the cambelt is not broken, and that there is no slack. Check that the water pump and idlers/ tensioners are all fine, as well. However, a broken cambelt usually causes a lot of damage to the engine. You probably need to remove the cambelt cover for a proper inspection - see e.g. picture 3:
How To.. replace a cam belt on an Alfa Romeo 2l engine

If not, replace the broken part and refit the cambelt and set the TDC etc. If a cambelt is due for replacement (every 3 years or every 36.000 miles/ approx. 60.000 km - and in case the water pump is not metal replace that as well) you might want to consider replacing it – at least if you want to keep the car. Replacing also makes it necessary to refit or even replace the balancer shaft belt:

Changing the balancer shaft belt on a TS or JTS engine

On this film at least the basics can actually be seen:

In case this has already checked out as OK, I’d also suggest checking the compression. I have to agree, that one or more broken valves might be a possibility, but also a broken piston or piston rings is also possible. Also a camshaft might be broken, but personally, I don’t think that a valve spring is the most likely to be causing this problem, though.

If you are not a mechanic or have not changed an engine valve or a camshaft (or in case of the head gasket) before, I’d strongly recommend that you either buy a workshop manual:

Alfa Romeo 156 Workshop Manuals

…– or find a mechanic who have experience with Alfa Romeo.
 

·
Registered
Joined
·
465 Posts
EngholmP,
The salient detail here is that there is a tappet which is not coming all the way back up as the cam lobe rotates onto the 'base circle'. This is causing a large gap to open between the tappet face and the cam lobe (from description, well beyond the slight clearance one would expect when the tappet is unpressurised). The tappet isn't seized because it can still be moved manually (lifted with fingers to close the gap). The only thing which can cause this is a failure for the valve to push the tappet against the cam lobe.

By far the most likely thing to cause this is a bent valve stem (preventing the valve from fully closing). A severe accumulation of carbon deposits on the valve stem could conceivably prevent the valve from closing all the way (and thus the tappet wouldn't follow the cam lobe onto the base circle), but I'd be surprised. A broken valve spring is also theoretically possible, but IMO far les likely than a bent valve stem (and remember that there are two springs per valve...). Remember that it is reported there has been a problem with the timing belt tensioner....

Whatever the problem actually is, I am as sure as I can be from the description that the head will have to come off...

Regards,
John.
 

·
Registered
Joined
·
1 Posts
Vote for tappets (which isn't to say it couldn't possibly be something else).

FWIW, I think 5w-30 is too thin for these engines, especially at operating temperature. The thinnest oil I've used in my TS engine is 10W-40, with which I found the engine to be rather noisy (somewhat 'clattery' in general, I suspect tappets and maybe some piston slapping, and, variator noise very noticable at start up). Since then I've tried 10W-50 (better, i.e. general clattering and variator noise lessened), 10W-60 (better again), 15W-60 (better still), and 20W-60 (no noticable difference to 15W-60). These are all Penrite oils, though some are "full synthetic" (whatever that actually means) and others not. I can't recall which was which, but my current fill is 20W-60 "high performance mineral".

Also, the thinner the oil is or becomes over time, the more of it my TS engine consumes, but even using 60 weight oils it goes through a significant amount (especially compared to my previous Honda and spouses' Saab, both of which consume near enough to zero oil). As the oil ages it seems to become thinner, judging by the increasing engine noise, the variator becoming more noticable at start up, and the rate of oil consumption accelerating. New oil and it all quietens down, and picks up a bit of power...

Regards,
John.
Hi John
Your are spot on. Same symptoms as my 147 TS 2.0. The engine is quietest with 15W-60 or 20W-60 but still consumes more oil than my 3.0L Busso.
 

·
Registered
Joined
·
589 Posts
Ok, everyone STOP!

As John and others have suggested its bent the valves.

As I initially suspected back at post #27 there was something wrong with the cambelts, as it turns out it was the cambelt tensioner that has failed. This has obviously allowed the belt to slip/jump, thus throwing the valve timing out, bending valves, thus engine losing all compression and power.

Pretty obvious by the lifter stuck down and all the other indicators.

There is nothing left to do but have the head removed and see how much damage there is, doing anything else in my opinion is a waste of time, it's just my opinion. Unfortunately, from what I hear in the second video, its NOT going to be just one valve, and it ain't going to be pretty. :eek:

Like I said, just my opinion, but i have seen this happen just too many times.
 
41 - 52 of 52 Posts
Top