12 replies to this topic

[spiguy]

Hi all,

 

I have posted in another thread about a cold start tappet noise I have which goes away after a minute or two. I thought it might be rocker shaft wear, and replaced that, but it still does it.

 

I am starting to think it is just down to a lack of oil flow at cold start, as if I pour some oil in it goes quiet straight away. I have run the engine with the rocker cover off, and there is oil getting to the rockers but I don't really know how to be sure its enough (I am wondering if there is reduced flow which is worse when cold as oil is thicker). I am using Halfords 20/50 oil, and have good oil pressure (60psi). As an indication of the oil supply to the rocker area, if running with the rocker cover off after about 2 minutes running small oil pools will form which would start to run off the side of the head if I kept it running.

 

One thing I do wonder is whether it is actually lack of oil at the rockers, or the camshaft area as when I slosh some oil on then obviously this will also flow down the pushrod holes to the cam lobes. Of course, maybe it isn't even a lack of oil but rather it is wear elsewhere such as followers, but it's just the way that it instantly shuts up if you slosh some oil on...

 

A couple of questions then :

 

1) can someone give an impression of how much oil flow they have around the rockers? Is it just a small amount or should it 'overflow' very quickly if the rocker cover is left off?

 

2)Any thoughts on whether it is likely to be cam lubrication ?

 

3) I had the 1st pedestal off when changing the rocker shaft, and checked that the hole in the pedestal was clear (it was) and I poked something (wd40 tube) in the hole in the head, which seemed clear but then it only went in a couple of mm so I presumed that the hole was a drilling into a horizontal oilway. Does that sound right?

 

4) Any sort of workaround to this  - ie any way to get some additional oil going up there?  I know that's not the right approach as it is masking the 'problem' but humour me

 

Thanks

Edited by spiguy, 10 June 2015 - 09:53 AM.

[Ethel]

There's a diagram somewhere.

 

If I recall there's a drilling to the front cam bearing and one from there to the front crank main: plenty of scope for bleeding off pressure. Wouldn't have thought the followers would be an issue (unless they're the drilled type), little buckets that will throw out their contents on the first up stroke.

 

Push a rocker along its shaft to see how quickly an oil film develops.

[spiguy]

There's a diagram somewhere.

 

If I recall there's a drilling to the front cam bearing and one from there to the front crank main: plenty of scope for bleeding off pressure. Wouldn't have thought the followers would be an issue (unless they're the drilled type), little buckets that will throw out their contents on the first up stroke.

 

Push a rocker along its shaft to see how quickly an oil film develops.

 

Sorry if this is me being stupid, but I'm not sure what you mean about pushing the rocker to the side. With the engine running?  Do you mean to expose the oil hole in the shaft under where the rocker runs?

[mini13]

the oil feed to the rockers is restricted by the cam, there is a groove on the cam journel that alows a pulse of pil to the rocker once a revolution. so they dont actually get that much oil.

[spiguy]

the oil feed to the rockers is restricted by the cam, there is a groove on the cam journel that alows a pulse of pil to the rocker once a revolution. so they dont actually get that much oil.

Thanks, that is interesting to know.

[jaydee]

Only when cold, no noise once warm?

Sounds like a first sing of worn pads/shaft, anyhow a 20w50 grade wont help oil flow at start up, although slightly better oils like millers or valvoline will work better when cold.

[Ethel]

You won't manage it running! I mean run it for short while until just before you expect it to stop knocking. Turn it off and push an unloaded rocker along the shaft, against the locating spring. Though I doubt it's an oil feed issue if you can stop it by slopping some oil in. You could use an old style squirty oil can to aim some at the rocker pads etc. to see the effect.

[spiguy]

Only when cold, no noise once warm?

Sounds like a first sing of worn pads/shaft, anyhow a 20w50 grade wont help oil flow at start up, although slightly better oils like millers or valvoline will work better when cold.

I've had all the rockers off and renewed the shaft. All the rocker pads look good, mostly just polished looking, no wear edges to speak of. 

 

Think the next step is to narrow down exactly which rocker it is!

[Blatherskite]

Have you tried the screwdriver stethoscope approach? Start the car cold, and locate the area you think is where the noise is, and test each part with a screwdriver pressed against it and the blunt end in your ear. Listen for loud tappity noises... The louder it gets, the warmer you are.

[spiguy]

Have you tried the screwdriver stethoscope approach? Start the car cold, and locate the area you think is where the noise is, and test each part with a screwdriver pressed against it and the blunt end in your ear. Listen for loud tappity noises... The louder it gets, the warmer you are.

 

Yeah, tried that and it didn't help me very much unfortunately! It doesn't seem to get transmitted into the metal work of the rocker cover for some reason. The best way I think to try to track it down will be just starting the car with the rocker cover off, and dribbling oil on different bits until I find it. The annoying thing is that you only have a short space of time to mess about before it goes away and it only ever does it on a proper cold start, so I only really get 2 chances a day to do it, and one of them is before setting off for work which is unfortunate as I tend to run late...

 

I'm going to start the process today though properly, and I plan to start off by dribbling some oil down the pushrod holes initially, with none going on the rockers, to see if it is follower / cam related. If not, then I'll move on to the rockers.

 

Thanks for the suggestion 

[Spider]

Not sure what your experience is with Minis but they do have a solid tappet and when cold are a little noisier than most other modern cars.

[nicklouse]

Have you changed the rockers? Have you checked that the oil feed is on the correct post etc.

[spiguy]

Thanks guys. Yes, I know they can be a bit tappety but I have never had this and have owned several minis over the years. It is definitely one specific rocker / follower / whatever. Not really worried about it or anything, it just has me confused and of course I would rather sort it if possible.

 

Nick, changed the shaft but not the rockers. I had bought a set of forged rockers off minispares, but unfortunately they weren't quite right so are going back, however the rockers I took off seemed in very good condition indeed so I was happy enough to refit them.