Rover 25 16v - Engine knocking sound

I have a Rover 25 16v and when I start it up from cold (or after 8 hours rest) a sharp knocking sound occurs from the engine. It starts about 5 seconds after the engine fires and continues for 12 seconds. Then the noise disapears.

I done a 70 mile round trip on the motorway each day. The engine has done 20,000 miles.

The main dealer has changed all 4 pistons, liners and con-rods and said it was due to a faulty batch of pistons/liners. 5,000 miles later the engine is making the same sound.

I have recorded the noise and worked out that it is happening at half the engine speed. Go to

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tohear the engine for yourself. Can someone tell me what this could be and if it may be cuasing damage.

Best regards

Martin

Reply to
colenum
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My Rover 200 (1999) makes exactly the same noise as this when started for the first time everyday. My local garage had a quick look at it while it was in for a new exhaust and said that it could be the tappets. Whether they are right or not I don't know as we haven't investigated it further due to a shrotage of funds.

Reply to
Melanie McDonald

Hydraulic tappet especially since it's half engine speed. Mine sounded just like that when one started leaking as well - never caused a problem for 30k until I finally had the cambelt changed and swapped the bucket as well. It goes quiet as it pressurises itself - you want to try a K series that's been stood two months and all 16 do it at once. I sincerely hope you didn't pay for the liners and pistons yourself as any smart mechanic would have been able to tell you the answer in 30 seconds.

Reply to
Chris Street

Yep. Sounds like the hydraulic tappets. Provided it goes away after the car has been running for a few seconds, I wouldn't worry.

Reply to
Moray Cuthill

I've just dug my manual out for the old 214 which has the same K-engine. Ten minutes! for empty tappets is acceptable and a "few seconds" is OK if it's been stood overnight. If it's under warranty though get it sorted as it'll make it more awkward to sell.

Reply to
Chris Street

I get this sometime as well. Seems to go away quicker if I rev the engine a bit - gets the oil flowing quicker. Also - check the oil level regularly. last summer I noticed my engine was quite loud at idle and I checked the oil and there was none on the dipstick! It took about 1/2 a big container of oil to get it back to full! Seems the K-series uses a bit of oil in use, a lot of engines do apparently.

Reply to
neutron

Your clue is that it happens at half engine (crank) speed. The camshafts rotate at half crank speed so the noise is related to the camshafts, followers or valves. I can tell you that many Rover engines (and I think the 25 uses the K-series) have hydraulic cam followers (tappets) which use oil pressure from the main oil pump to expand themselves and take up any slack between the camshafts and the valves - this is confirmed by the noise disappearing after a few seconds running.

So it's probably going to be (in no particular order):

1) Knackered hydraulic follower (unlikely if the noise does disappear reasonably soon after start-up) 2) Low oil pressure or partial blockage (unlikely on an engine that's only done 20K unless there are other symptoms too) 3) Wrong grade of oil (too thick) - the effect of which will be worsened in cold weather as oil is thicker when cold than when hot.

Of the three choices I think that the last is the most likely in your case, given the time of year, etc. You might want to try a 'thinner' oil (certainly not 20W/50 you can get for £1.99/5ltr from Wilko!). Another possibility is an oil filter with a non-return valve fitted which will prevent the oilways in the engine from draining back through the filter when the engine is not running - this won't cure your problem but might shorten the time it takes to quieten down.

Darren

Reply to
Darren Jarvis

Listening to the sound it does NOT sound like its at half engine speed, and certainly not a single hydraulic lifter noise- this would be once every 4 rotations of the crank.

It sounds like a bottom end problem of some sort to me.

Tim..

Reply to
Tim (Remove NOSPAM.

I have processed the mp3 file on a PC. This shows the noise peaks at

10 or 11 times a second, giving 600-660 times per minute. Given that the engine goes at about 1200rpm after turning the key, it must be half engine speed.

New theories are piston slap or bore washing. Has anyone experienced this on the K series engine? If so, how was it cured?

Thanks

Martin

Reply to
colenum

Eh? The camshaft goes round at half engine speed and therefore hits each follower once per rev. So each follower gets depressed once every two crank revs.

Also it's certainly at half engine speed.

Reply to
Chris Street

Which makes it a camshaft problem. Forget the bottom end.

Which go ping once per rev. It's not these.

It's a follower. Put up with it or get the garage to sort it under warranty.

Reply to
Chris Street

sounds hydraulic tapet to me

Reply to
George Spigot

Your clue is that it happens at half engine (crank) speed. The camshafts rotate at half crank speed so the noise is related to the camshafts, followers or valves. I can tell you that many Rover engines (and I think the 25 uses the K-series) have hydraulic cam followers (tappets) which use oil pressure from the main oil pump to expand themselves and take up any slack between the camshafts and the valves - this is confirmed by the noise disappearing after a few seconds running.

So it's probably going to be (in no particular order):

1) Knackered hydraulic follower (unlikely if the noise does disappear reasonably soon after start-up) 2) Low oil pressure or partial blockage (unlikely on an engine that's only done 20K unless there are other symptoms too) 3) Wrong grade of oil (too thick) - the effect of which will be worsened in cold weather as oil is thicker when cold than when hot.

Of the three choices I think that the last is the most likely in your case, given the time of year, etc. You might want to try a 'thinner' oil (certainly not 20W/50 you can get for £1.99/5ltr from Wilko!). Another possibility is an oil filter with a non-return valve fitted which will prevent the oilways in the engine from draining back through the filter when the engine is not running - this won't cure your problem but might shorten the time it takes to quieten down.

As for damage, well that depends on how you define it. What will happen is that it'll wear the cam lobe(s) quicker than usual as instead of a gradual push down it will hit the follower like a hammer (damped a little by the valve spring) - hence the need for as small a clearance as possible without risking the valves not closing fully due to heat expansion.

Darren

Reply to
Darren Jarvis

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