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Hi guys.Question on behalf of my daughter please.She has an MG ZR,one year old just had 12k service.Not immmediately after the service,but recently the engine on start up has begun to really rattle for some 12-15 seconds whilst cold then is as good as gold and purrs away nicely.Is this normal or or is it that the weather has suddenly got a lot cooler of late? To me ,it reminded me of a typical Vauxhall camshaft on the blink or maybe its just cold-tappet hammer.Any advice appreciated.Mose

What model is it Mose?

I assume it's not a Diesel ZR (these sound like tractors anyway, surprisingly fun to drive, but sound like a diesel).

Which leaves one of the K series engines.

the 1.8 K and in particular the VVC version is known for making a tappety sound when cold (and sometimes when not, but usually this noise goes when the engine satrts to warm up).

The K engine has hydraulic followers in the head, these are cylindrical metal billets that sit in a pocket and rely on oil to suspend them and keep them lubricated. The cam lobes activate directly on the followers and the followers activate the valves.

After switch off the oil tends to drain somewhat into the sump, then as the temperature of the engine cools the oil becomes more viscous. This means that when you start the engine and it is on the warm up cycle the oil needs to be pumped up to the head and fill the follower pockets, this becomes more effective as the oil temperature rises and the oil becomes thinner. During this time the engine may be a little noisy, but providing the correct oil is used and the car isn't reved hard from cold all the time it should cause no damage. In my MGF there is an oil temperature guage and i don't work the engine hard until it has reached at least 90 degrees, the ZR i believe doesn't have an oil temperature guage, so as an assumption it takes roughly the same time again to get the oil up to temperature as the water.

It is also important therefore, to prevent excess drain back into the sump that low viscosity fully synthetic oils (such as Mobil 1 for instance) are not used as this can promote wear on the cam followers. I beelieve MGR specify GTX Magnatec for this very reason.


Scarlet Fever

The whole thing about hydraulic tappets is that they require to be 'pumped up' to reduce valve clearance. The longer they take to pump up the more noticeable the noise from excessive valve clearance. In reality hydraulic tappets shouldn't loose all the oil at shut down and therefore should pump back up very quickly at start. Therefore, I would have thought that low viscosity, i.e. 0W40 would have been better at getting the oil pumped up to the top of the engine quicker and start its lubricating better. Magnatech may be very good at adhering to surfaces but it is not as good as a fully synthetic package like Mobil 1 at preventing oxidation. An oil must offer all round protection and the tackiness agents in most top API SL rated oils have a similar performance to Magnatech. I have heard internal engineers at Castrol state that Magnatech, like the 'Liquid Tungsten' logo a few years back is 90% marketing and 10% reality.

With many short trips experienced in low annual mileage 200/25/ZR's the oil is prone to more rapid oxidation from condensation in the engine in a 12 month (MG R specified) interval and thus this oxidation can lead to some clogging of the hydraulic tappets causing the same symptoms listed above on the K series. In addition, the depositing that occurs in cheaper oils will also lead to sluggish behaviour of the tappets and therefore a fully synthetic oil will be far superior at maintaining internal cleanliness and minimising depositing altogether. If the engine oil has been allowed to form varnish and lacquer etc then chances are the oil ways are reduced (taking longer for oil to pass through to tappets) and/or the relief valve in the hydraulic tappet body is gummed up and not allowing the tappets to come up to pressure. This can often be rectified by using a PolyAlphaOlefin based synthetic oil. In this respect, modern synthetic oils are definitely far superior than 10 years ago at preventing the depositing (rather like cholesterol).

In Winter cold starts, a 0W40 will be better than a 10W40 or 15W40. They will all offer SAE 40 viscosity protection when warm, but the 0W will flow more readily than the 10W or 15W. Also, a 40 at operating temperature is still thinner than a 0W or 10W at cold. However, a cheaper 10W40 can shear more readily than an expensive 0W40, and the end result is that a cheap 10W40 can have a warm viscosity equivalent to a SAE 30, whilst a good quality 0W40 will maintain its warm operating viscosity of SAE 40. The warm viscosity of 40 is achieved by additives which expand when warmed in the engine oil causing it to thicken and act like an SAE 40, hence these are susceptible to shear in boundary contact zones such as the cam and gears etc. In fact, a fully synthetic oil is usually also far superior at providing film strength between hydrodynamically loaded components like the bearings. Although viscosity has an impact, the thicker the oil, the greater the drag on the bearing, and the risk of overheating and oil film strength breakdown. A top quality oil such as some motorsport people use like Royal Purple is even better at providing a far greater film strength without increasing viscosity necessarily, and a combination of this oil type with a quality petrol will offer >5bhp more, along with better fuel economy and long term reduced wear with a better chance of maintaining the economy and performance at optimum levels over the engine's life.

At the end of the day the major brands are producing an oil down to a price that is accepted by the motorist. I.E., as cheap as possible. Many of the sponsored motorsport vehicles are not running on the actual sponsor's oils, but a better quality oil. These are simply commercial deals. Of course, if one were prepared to pay much more for their oil, then the additive formulation and refining/blending would be better than it is. Aftermarket additives exist because the oil companies don't put them in in order to keep the oil 'affordable' to the general public. However, my preference is to pay extra for a quality oil that is blended with the additives at source thus minimising risks of adding additive to a standard oil. These risks can include the additive causing the oil to do one function extremely well and at the same time causing the other five functions of the oil to perform badly.

Selecting oils and petrols is a matter of personal choice based on planned length of ownership. Anyone planning to keep their car over a 5 year or 150k mile period would do well to consider either more frequent oil/filter changes every 6k miles (the dealer specified is a commercial compromise to make cost of ownership look attractive). Or spending more on a quality oil and fuel.

For the average motorist, this is a perceived waste of money since the car is often kept for no more than 60k miles, and the considered view is that the 2nd owner will have to worry about the wear and tear. However, as several case studies have proven for fleet/taxi operators, good quality oils and more frequent oil changes prove more cost effective reducing vehicle downtime and allowing the vehicle to comfortably exceed 500k miles on the same engine without need for attention.
As the owner of the famous 2 million mile Volvo advised, stick with a brand of oil and fuel to minimise cross contamination of the different additive packages, change the oil and filters (air/oil/fuel) regularly, allow the engine to warm up properly, avoid unnecessary start up and shut down, and do not load it in too high a gear at low speed.

Apologies if this has run on somewhat but being involved independently in the oils business (I don't sell oils or filters, merely train and consult) I hope this has straightened a few issues.

never heard of Royal Purple until now. Is it expensive and where do you get it.........?

Noticed the Purple Ice too, which is radiator coolant and says it will reduce engine temperature. Anyone tried?

Martin, one of the most useful and informative posts seen in a long time - thank you. I will stick to my policy of using only French 5/50 Mobil 1 in wife's MGF and my Montego turbo, and changing every 6k miles or 12 months whichever comes first.

I noticed the same problem

after the first service, n some mouths later, the engine started to make a fecking diesel noise...

like u said tractor pawwwaaaaa

I bring it back to my dealer n he said it was the hydraulic tappets....
n with the very hot weather the oil can be much more fluid

now temp is around 20/25C n it still makes this diesel sound, but less loud (I hope it's not my imagination to reassure me ;o) )

maybe with another oil than the 10w40 one?? but I don't believe it....

Royal Purple is available from the web site link, they don't sell through distributors. Very good results in racing etc, and the cost long term is outweighed by the savings in reduced oil changes and engine rebuilds if you are into serious track day work. For normal daily use, probably difficult to justify unless you are absolutely devoted to your car!
As to the coolant, I haven't tried it so can't comment.

Hope that helps

I think I'll give the coolant a go, it beckons to my curious mind. If it cost under 20 quid after VAT and delivery, then it's worth a small risk. Keeping things cool seems to be a theme on here with mods and improvements. Perhaps I'll keep the bottle until the next service at 2 years when the coolant is replaced. The last maintance sheet states - replace every two years AFC and every four years XLC (OAT) .....

Dealers have been replacing piston and liners like they are going outta fashion in an effort (usually successfully) to cure this tap tap tap noise on the K Series engine.

Hi guys,thanks for all that.Her car is a 1.4 ZR(and ,ironically ,she works for Shell Lubricants!).

The car was standing for some 7 hours today after a 35 mile run and it was a very warm day.When the car started it was noticeably quieter.I think you are probably all pretty accurate-we'll live with it and monitor it(oh,MGs)Thanks again.

PS I have an F VVC and have never experienced any untoward engine noises,but then again it lives in a nice warm garage and doesnt go out in winter so maybe that makes a difference.

PPS Sorry for so long in acknowledging your advice,we've been away on hols.Thanks again.

Another useless posting from Eric, how can replacing pistons and liners cure a tapping noise from the tappets?


Don't be a c**t all your life - I was referring to piston slap - w*nkshaft.

This thread was discussed between 02/09/2003 and 19/09/2003

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