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post #1 of 12 (permalink) Old 29-06-2010, 20:51 Thread Starter
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tappets knocking sound.

Hi guys do you know why my 53 plate rover 25 engine always knocks when cold not really sure what part of the engine its coming from. I thought it was piston slap but it goes away after the engine has warmed up but it can be sluggish when cold. Since i've had it (1 year) its had a proper service. Any solutions ?
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post #2 of 12 (permalink) Old 29-06-2010, 21:09
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low oil is all I can sya I only noticed today I have been running round sweet two thirds of F all when it comes to oil ! I was like CRAPPPPPP!! express factors here I walk! lol cost me like £18 for decent oil. if it has a decent amount of oil in the engine your bottom end shells might have gone. =[

Edit: But I doubt it because it goes away when it is warm , maybe your tappets just aren't receiving the oil, system flush ?
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post #3 of 12 (permalink) Old 29-06-2010, 21:13 Thread Starter
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what is a tappet ? How would i cure the problem ?
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post #4 of 12 (permalink) Old 29-06-2010, 21:15
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I'd go for piston slap, this will go off when warm. This was common when under warranty, we did used to do about 3 or 4 a week. The cure was new piston/liner assemblys which had teflon pads on the piston so rather than being noisy after as little as 5000 miles they lasted until out of warranty! Megabucks job, as long as it goes off then just ignore it.
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post #5 of 12 (permalink) Old 29-06-2010, 21:17
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wikipedia is my friend =D
http://en.wikipedia.org/wiki/Hydraulic_tappet
If I remember correctly k series have hydrualic tappets(lifter) and when your oil runs low you get the tapping noise, untill ti has warmed up and the oil has reached the tappets =] hope this helps =D basically just check your oil, if it is on the low side top it up go for a 20 minute drive come back turn off the car wait till the morning and start it up again and it shouldn't make that sound =] My car is perfect atm =D no need ofr oil changed anymore it looses almost all of it's oil in ...10 K so about every 9K I just fill it up =D PERFECT=D I know it is wrong but shh you all I am lazy =P
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post #6 of 12 (permalink) Old 29-06-2010, 21:21
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A tappet is a cam follower - it is what connects the valves to the camshaft cam lobes. Its job is to take up the slack between the 2 parts. The slack varies when the engine is hot as parts expand with heat. It fills with oil under pressure from the oil pump and its little piston is pushed outwards against the valve stem and takes up the slack. If the pistons in the tappets stick or get seized, they wont work properly and will not take up the slack, or not allow enough slack, causing compression loss around the valve seats due to the valves not quite being able to close properly.

The best bet is for you to change the oil and then add some Wynns hydraulic valve lifter treatment from the motor factors. Leave this several weeks to allow it to try to clean the tappets and valve gear.
If this doesnt work, then you will have to strip the head and either overhaul the tappets, or replace them - not forgetting there are 16 of them, and they are not cheap!
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post #7 of 12 (permalink) Old 29-06-2010, 21:22
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What grade of oil was used when it was changed should be 10/40
try an oil and filter change with a flush first.
Tappets is an old expression hydrolic valve lifters would be a better term basically these fill with oil and maintain the correct clearence between the camshaft and the valves in the cylinder head of the engine. If these are not filled correctly with oil (which can happen when cold if the oil is old/sludgy/wrong grade) then the gap is too wide and the tapping noise you hear is the camshaft hitting the valve lifter as it is not maintaining the correct gap.
Just a quick thought what colour is your oil (if its creamy you may have head gasket trouble with water in the oil)
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post #8 of 12 (permalink) Old 29-06-2010, 21:31 Thread Starter
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Thanks for your help guys i now understand what a tappet is and what it does . I will try wynns stuff and see how that goes i just added 10/40w as when i checked the oil it was about half on the dip stick. My oil colour is black thankfully! Touch wood! I check my coolant everyweek although recently its gone down a smidgen but its still over the min, i will keep my eye on this though. Thanks guys
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post #9 of 12 (permalink) Old 29-06-2010, 21:53
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The fact that the oil is black is actually a bad sign - it means the oil is knackered!
Oil should be a clear light brown - it goes black when its contaminated with carbon and engine deposits.
Drain all the oil, replace the filter, then add a 4.5 litres of 10W40 semi. Then add the wyns - this will stay in the oil to the next change.
Its really best to change the oil twice a year, or every 6000 miles, whichever comes sooner. If you do this religiously, the oil should not turn black again, and the tappets will then look after themselves.
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post #10 of 12 (permalink) Old 01-07-2010, 21:16
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If the rattle occurs at roughly half engine speed then it's a lifter, if it occurs at engine speed then it will be piston slap.
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post #11 of 12 (permalink) Old 01-07-2010, 21:30 Thread Starter
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half engine speed ? Do you mean idle ?
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post #12 of 12 (permalink) Old 02-07-2010, 21:52
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No, It's a bit hard to describe but basically the camshafts rotate at half the speed of the crankshaft so a cam/lifter noise will sound a bit slower than a crank or piston noise. As I say, a bit hard to explain so may be an idea to track down someone who has a bit more experiance for a second opinion.
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