Hi every one

 

I have a  June 2013 Fabia 1.6TDI 105 bhp Elegance Estate and I have done 18,500 miles.

 

Starting it this morning, not having used for two days, I heard a rattling noise from the engine which sounded similar to the old rattling tappets.

 

I can only assume it is one of the hydraulic tappets sticking due to lack of oil?

 

I am going soon for a 20k service but wondered has any member had a similar experience.  The noise disappeared after few miles.

 

Thanks

Brian 

 

My car does this as well. I assume it is simply the oil making it`s way around the engine after having settled in the sump for a few days. I normally leave the engine run for a couple of minutes before pulling away.

 

My car has done 41000 miles and has given me no problems.

Worth asking as you're going in for service, it's under warranty after all. May pay to drop it off the evening before so you can ask them to get a technician to start it from cold and give expert opinion.

Most dealers will oblige. Let us know how you get on

Diesel Estate, your engine shouldn't be making a rattling sound that goes away after a few miles. It does, as you mention, sound like hydraulic tappet noise. If it takes a few miles to go away it probably means you have a faulty tappet or tappets. It would be normal if the vehicle had stood for many weeks, but not just for a day or two. It's usually impossible to find out which one/s are actually faulty and it's normal to replace the whole set. It's an easy job. Mention it to the garage and they will decide what to do. They may suggest having the service to see if that cures the problem (new oil etc), but usually it won't. Let us know what happens. 

Edited 22 April, 201412 yr by Estate Man

Hmm. Mine does this too. Had assumed it was normal. Checked oil level and it's as it should be. Will be following with interest!

My car does this as well. I assume it is simply the oil making it`s way around the engine after having settled in the sump for a few days. I normally leave the engine run for a couple of minutes before pulling away.

 

My car has done 41000 miles and has given me no problems.

It's recommended in the manual that you drive away after starting, as it warms up quicker when driving, and leave running for 2 mins after a run to cool gently.

Tony

I probably dont leave it a couple of minutes, more like whilst I put seatbelt on etc

Thanks every one for your replies.

 

I let the car idle for at least a minute after a long run to let the turbo run down gradually and the oil flow to cool the turbo bearing.

 

Thanks

 

Brian

Not sure if you need to do that on a crtdi engine they don't like sitting in idle for no reason

I dont think the cr engine runs an aux pump to cool down the turbo if its too warm when shut off.

Some cars do, but i dont think the cr does.

Id let it cool down if it was me. Just a few minutes on idle before shutting off

Just a thought. Diesel engines rely on the compression stroke to raise the air temperature and start the iginition process as the fuel is injected.

 

Starting a cold engine requires an air heater in cold weather. The point is that the compresson is barely enough to heat the air to get reliable fuel combusion when the engine is cold.

 

Now once the cold engine starts it is taking in cold air and combustion will be a bit rough. Hence the rattling sound. Once warm, the engine will sound much smoother.

 

Turbo-charged engines have a compression ratio around 18:1. Normally aspirated diesel engines have a compression ratio of around 25:1. This meant that starting requires a more powerful starter motor but the compressed air is significantly hotter with a cold engine. So there is a smaller tendency for them to rattle badly when cold.

 

If your problem were a sticking tappet, it would probably be worse with a warm engine (hence warm thinner oil) than when the engine is cold.

Just a thought. Diesel engines rely on the compression stroke to raise the air temperature and start the iginition process as the fuel is injected.

Starting a cold engine requires an air heater in cold weather. The point is that the compresson is barely enough to heat the air to get reliable fuel combusion when the engine is cold.

Now once the cold engine starts it is taking in cold air and combustion will be a bit rough. Hence the rattling sound. Once warm, the engine will sound much smoother.

Turbo-charged engines have a compression ratio around 18:1. Normally aspirated diesel engines have a compression ratio of around 25:1. This meant that starting requires a more powerful starter motor but the compressed air is significantly hotter with a cold engine. So there is a smaller tendency for them to rattle badly when cold.

If your problem were a sticking tappet, it would probably be worse with a warm engine (hence warm thinner oil) than when the engine is cold.

Ahh. So thats why the old transits dont need glow plugs? If they had a turbo, they would?

If the tappets were loose though, it would start off loud and get abit quieter as it warms up?

Theyre hydraulically self adjusted arent they?

Yes they use engine oil to hold the tappet with the correct clearance for the valves. It's a clever trick but can act as a rev limiter because at high revs the valves slowly stop opening as the revs increase.

 

The tappets can stop working if the oil supply is restricted (dirt) or the seal is worn in the tappet. I had this with my last car. A good engine cleaner will fix the problem. I use a product called Forte. It isn't officially sold to the public but you can get is on the Internet. It is very good and effective with an older engine (100,000+ miles).

 

As regards noisy tappets getting quieter, it is my experience that anything mechanical that rattles when cold rattles more when warm. There could be exceptions though. My experience is based on cold oil being more viscous and therefore better at deadening sounds in the engine than hot thin oil. I know modern synthetic oils are very good at reducing this change of viscocity as the temperature rises but they can't compensate completely for temperature.

 

Regarding old diesel engines, the stresses from a high compression ratio and the associated high combustion temperatures make big demands on the strength of the engine. As I reported earlier, with an 18:1 mechanical compression ratio plus a turbo-charger doubling that, the effect is like having a 36:1 compression ratio when the turbo is working. That's about as high a compression ratio as engines get currently.

 

Interestingly, modern gas turbines in jet aircraft run at about 40:1 and acheive very high fuel efficiencies partly as a result. The engine designers are trying to raise this to 70:1 at present but it is a daunting prospect. The gas leaving the combusion chamber is already hotter than the melting point of the metal in the combustion chamber and turbine blades with a 40:1 compression ratio. This is made possible by blowing cooler air from the compressor through the inside of the blades and around the combustion chamber.

 

While valves and pistons in a diesel engine don't face quite the same conditions since combustion is intermittent rather than continuous but cooling them is a limiting factor. When Rolls Royce faced this problem with the Spitfire engine they invented hollow valves filled with sodium. This melts inside the hot valve and carries heat from the valve head to the stem where is is cooled by the cylinder head. This makes the valves expensive but it shows you what can be done. The pistons are cooled by spraying oil onto the inderside of them from below.

 

Sorry if I am rambling but you might find this of interest.

I do find that interesting

Cheers .

Thanks everyone

 

Well as you might expect the dealer found no fault and would not replace the valves with the usual excuse, Skoda will not pay for work unless fault is detected!

 

Not heard the metallic tapping noise since, so only can assume as stated in SlowBloke's e-mail it may have been a bit of dirt in the oil channel?

 

Diesel Estate