Engine Noise

[Smithy007]

All - top end of my engine is a bit noisy (tappety) on start up and for the first 1/2 a mile, then quietens down completely and is fine thereafter - should I be concerned / do I need to do something about it - any thoughts ? - cheers - Smithy

[Rob.]

The noise you hear is as a result of debris and crud build up in the oilways of the lifters. It is not a big deal, as long as the noise goes away. Most cars do this, but some only for a very short period of time. The longer the noise lasts, the more blockage you have.

So to understand the problem, lets first look up the definition of a hydraulic lifter (from wiki):

'A hydraulic lifter, also known as a hydraulic tappet or a hydraulic lash adjuster, is a device for maintaining zero valve clearance in an internal combustion engine. The conventional means of adjusting valve actuation always requires a small clearance to be left between the valve and its rocker or cam follower to allow for thermal expansion and wear. The hydraulic lifter was designed to ensure that the valve train always operates with zero clearance, leading to quieter operation and eliminating the need for periodic adjustment of valve clearance.

The hydraulic lifter consists of a hollow expanding piston situated between the camshaft and valve. It is operated either by a rocker mechanism, or in the case of one or more overhead camshafts , directly by the camshaft. The lifter is filled with engine oil intermittently from an oil gallery via a small drilling. When the engine valve is closed, the lifter is free to fill with oil. When the valve is opening and the lifter is being operated by the camshaft, the oil feed is blocked and the lifter acts just as a solid one would, oil being incompressible.'

So we can see that the lifter needs to fill with oil, and herein lies the source of the noise.

Taken from another web site:

'The tappets use engine oil under moderate pressure to 'pump up'. The idea is that the valve clearance is always zero, irrespective of engine temp, because the tappet adjusts itself by squirting out oil it doesn't need. This leads to more accurate timing (compared to solid lifters) and zero maintenance (no need to adjust the valves)

'Sticky' tappets don't only make the car sound like a diesel, but also allow increased wear on the valvetrain and fudge the valve timing as well.

The main reason the tappets 'stick' is that carbon and crud are obstructing the tiny oil passages. This means that the oil cannot move in or out through the holes - strange how 'thicker oil' is passed on as a remedy. In severe cases, all the flushes in the world won't clear up the holes, the tappets have to come out, be dismantled and cleaned properly.'

The reason the noise goes away, is because as the engine heats up, the oil thins and the oil is able to flow more easily into the tappets through the blocked oil ways.

From another site:

'The solution therefore is to care for the engine a little more. The small oil ways in the tappets are prone to clogging up with oil debris, which can come about by using poor oil or skimping on the oil changes.'

And from wiki again:

'There are a number of potential problems with hydraulic lifters. Frequently, the valvetrain will rattle loudly on startup due to oil draining from the lifters when the vehicle is parked. This is not considered significant provided the noise disappears within a couple of minutes, typically it usually only lasts a second or two. A rattle that does not go away can indicate a blocked oil feed or that one or more of the lifters has collapsed due to wear and is no longer opening its valve fully. The affected lifter should be replaced in the latter situation.'

In conclusion:
If you have noise in the tappets from start up, it is either oil starvation due to blocked oil channels or a worn / damaged tappet. The way to tell the difference is if the noise goes away within a few minutes, it is the former. If the noise persists, it is the latter. The solution to the blocked oil channel is to do more oil changes and perhaps use an engine flush, and do more regular engine oil changes. If the blockage is bad, clean the tappets.  The solution to the latter is to replace the tappets. Replacing the tappets (which people on other sites recommend) is a waste of money if you only have a blocked oil channel.

[Oil-C]

Brilliant responce. Sounds like an easyish job, would the whole cylinder head need removing or just the rocker cover? I guess just the latter? If it is the latter then I might give mine a little clean!

[Smithy007]

Rob - thanks - the car's just had fresh oil and new filter, so perhaps a flush is in order (??) - what's the answer to Oli-C's question, please - is this a straightforward job that I can tackle myself ? (I'm reasonably hands on, albeit clearly no expert!) - is there a technical guide for doing this that I can gain access to ? - cheers again - Smithy

[Rob.]

Taken from the haynes manual, this will give you some idea on the process involved.

Note: Suitible sealent will be required to use between the camshaft bearing housings and the cylinder head on refitting, and a new valve cover gasket will be required.

Removal
1. Remove the timing belt
2. Disconnect the accelerator cable and position it to one side
3. Remove the spark plugs and distributor
4. Unbolt the spark plug tube housing from the top ov the valve cover
5. Disconnect the grankcase ventilation hoses, then unbolt the valve cover from the cylinder head and remove the double gasket (this may be in two sections or joined)
6. Remove both camhaft sprockets
7. Using a dial guage, measure the endfloat of the camshafts. This will give an indication of the amount of wear present on the trust surfaces
8. Progressively slacken the camshaft bearing housing bolts on both housings until the valve spring pressure is released
9. Note the position of the cam lobes; the lobes for No1 cylinder (flywheel end) will be pointing upwards. Remove the camshafs from the clylinder head, together with the oil seals. It is not necessary to identify them, as the exhaust camshaft has a slot in the end to drive the distributor. Recover the inlet camshaft plug from the cylinder head
10. Remove the hydraulic tappets, noting which way round they are fitted, and place them in a compartmented box, or a sheet of card marked into 16 sections, so they may be refitted into their original locations.  Ideally they should be fitted into a compartmented box filled with engine oil, to prevent the oil draining from them

Inspection
11. Examine the camshaft bearing surfaces and cam lobes for wear ridges, pitting or scoring. Renew the camshafts if evident
12. Renew the camshaft oil seals as a matter of course. Lubricate the lips of the new seals before fitting them, and stores the camshafts so the weight is not resting on the seals
13. Examine the camshaft bearing surfaces in the cylinder head and bearing housings. Deep scoringor other damagemeans that the cylinder head and bearing housing must be replaced
14. Examine the hydraulic tappets for scoring, pitting and wear ridges. The tappets should be renewed if they are obviously worn, or if they are excessively noisey in operation
15. If new hydraulic tappets are being fitted, or if the old ones have been allowed to drain, prime them with fresh oil before fitting them, as follows. Immerse each tappetin oil with the holeuppermost, and use flat-nosed pliers and move them up and down until all the air is forced out