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MG MGF Technical - Valve rattle when hot - VVC F

After a moderate thrash (enough to move the oil temp up a notch more than normal), tappet/valve noise is plain to hear. It's behind the driver's head area and taps at - I guess - a quarter of engine rpm. Can anyone give me a clue what this might be please?

An engine oil flush and oil change with new filters all round, plugs and HT leads made a big difference to performance and "standard" tappet noise - the kind you get on cold startup with thick/old engine oil. It's now markedly less noisy on startup through to normal operating temperature - clean oil in clean oilways no doubt being the cure.

Over the winter break, I've had some work done to the "VVC F". headlights have resilvered, gear change cables renewed and a mechanic has fitted a new main timing belt, adjuster and water pump (it was leaking). Sadly he's overlooked changing the smaller timing belt (doh!). The motor has done just over 103 thousand miles and the timing belts and head gasket were changed under previous ownership at 65,000. It's great to be able to see at night and to have no more worries about HGF due to water loss from the pump. The old pump had a nasty water stain from the hole in the dry side of the casting. After a few hundred careful miles to let the new pump/cambelt/adjuster bed in it was a joy to let go a tad, although I've not gone past 6000rmp. The motor sounds and performs very well indeed and really opens out past 4000rpm - bestowing me with the MGF smile once again, until I return to idle and can hear the valve/tappet clatter.

Is the smaller timing belt something I can change relatively easily, compared with the awkwardness of changing the other belt? Might the fact of running an old with a new cam belt, contribute to the valve noise I get when hot?
J Lennon

IIRC VVC units can become noisy with age, which may have little import upon longevity but certainly annoying. That said, there are other noises that should be investigated - I'd suggest that you take your car to an expert in things VVC and get them to listen...

... and I'd certainly get that secondary belt changed, and ensure that the cam belt tensioner (manual, on your VVC) was changed - these can fail unpredictably and disastrously if not changed with the cam belt at its service point (frequently overlooked!!!)

Looks as though your tensioner was changed - which is a relief! :o)

Hope that you find the problem - do let me know how you get on.
Rob Bell

When having important parts fitted, I insist on having the used items left in the boot for my inspection. This goes some way to satisfying my technical interest and serves as a check the work has been done. Thus I'm fairly sure the cambelt tensioner has been changed. The old item seemed solid and I've every reason to suspect it had done over 100k miles. The cambelt and water pump had definitely seen better days though! She's back in the garage again Thursday for a professional valet to get rid of paint that's mysteriously appeared in the headlining of the hard top! The mechanic stashed the top somewhere safe - evidently too close to whoever was redecorating their offices! At your suggestion Rob, I'll ask for a second opinion/trained ear to report on the engine rattle and will publish the findings here. I hope it's not the VVC mechs, which I fear may be expensive and to replace and even trickier to overhaul. I'm reckoning the small belt is causing an out of sync condition to the mech run by the main belt - given the assumed difference in stretched length and flexibility of the old belt vs new. Maybe this is cause of rattle on idle, when hot. As this motor doesn't use or lose oil, I'm hoping money spent will be worthwhile for this second car that only sees half a year's leisure motoring.

J Lennon

Fingers crossed Jeff :o)
Rob Bell

Looks like I'm gardening again this weekend - mechanic hasn't returned the car yet (with report on rattle from a VVC 'expert').

J Lennon

Any news yet Jeff?
Rob Bell

I've got the car back, sans hard top, which still has paint on the head lining. Nice weather though, so top's down anyway!!

VVC rattle is most noticeable when oil temp is at over 90degrees, but remarkably quiet below that. Expert opinion on the rattle is "don't worry - they all do that sir, but it might be a lazy valve spring". My principle vehicle - a bmw 320d touring - has just thrown a crankshaft pully - so that's in for a 400 repair. It's a belt pulley with a doughnut centre which has come adrift from the metal centre that bolts to the crankshaft. When it's back I'll get the smaller cambelt in the F changed and see what difference, if any, to the clacking noise. If no improvement, I'll consider doing a head overhaul come the later autumn, given I've been told not to worry.

This week has been a lot of fun, being 'forced' into using the F for business on hot days, with the top down and buzzing through the gears. What a hardlife, but I can put up with it!

'Cos the garage made an accidental paint mess inside the hard top, they've done a jolly good valet of the entire car for free as a token gesture and I'm thrilled to bits with the shine inside and out. I'd bought a set of leathers for gear shift and handbrake on Ebay and the mechanics fitted these for me as well. What a decent crowd they are - Queens Park Garage in Bournemouth. I've done my share of the cosmetic overhaul over a couple of evenings - cleaned the soft top and reconditioned it with a twin pack Turtle Wax kit. Looks like new and should be more waterproof than before.

So.... there's still a bit to do.
1) Drain and replace hydraulic fluid in brakes and clutch.
2) Find and fit replacement heat shield over the silencer and go on to "mesh" the rear vents between the exhaust pipes. My heat shield has a gaping hold in the centre.
3) Get the suspension drained and repumped. Ride height is correct both sides, but a I think the up/down movement is insufficient. The ride is a bit harsh over bumps.
4) Get Toyo Proxes on all four, and toe in the fronts an extra 5 mins as per Rob Bell's excellent article and recommendation. See my recent post on handling issues.
5) Kill the intermittent boot leak - it's probably the rear light cluster seals.
6) Paint the soft top hood frame - black Hammerite would look good. Methinks removing the soft-top material will be a problem!
7) Attend to a few stone chips and have a couple of car park dings punched out.
8) Replace the non working pea bulbs in the clock and behind the water temp in the instrument panel.
9) Discover and remedy the rattle in the windows when they are "down".
10) Buy a set of his and hers MG caps and anoraks!
11) Drop some pics onto this site.
J Lennon

I've got that window rattle too Jeff - thoroughly annoying. It's one of those jobs I've been putting off for years! That, and finally sorting out the door glass leaks. And then there are the list of projects I have lined up for the car, including the heated seats (I still haven't figured out a satisfactory switch location/installation solution - and I want all this figured out in my head before progressing it any further!)

May be one day I'll have the time. Probably in about 26 years...
Rob Bell

I've got the window rattle fix kit now - a pair of window stops Mk3 I'm told. The rubbers are square. I hope the replacements will fix the rattle and the window alignment. My drivers door glass has dropped 3mm at corner over the mirror, where it meets the soft-top. I get a small leak here. Boot leak partly resolved (see separate post) - I have a new thick rear cluster seal to fit to the o/s.

Like youself Rob, I have the parts but need the time to fit them. At this time of year, by better half has me on gardening duty.

J Lennon

The old small cam belt was worn/slack; would that have put the inlet cams out of sync, or would the VVC mechs iron that defect out? With new belts and 250 miles of progressively harder treatment (mini running-in period) I believe the engine revs more readily than before. However, valve rattle is still present when hot - i.e. when oil temp gauge is one mark up from rest.


J Lennon

I've had "Dr Dave" (of the other forum fame) have a listen to top end rattle when hot. He says it's OK. He's heard a lot worse than mine and commented if it revs to 7k+ without effort, doesn't burn loads of oil, then there's not a lot wrong.

That's reassuring and confirms what others have told me.

Now all the standard engine service items have been done plus the essential replacements of timing belts, adjuster, w/pump and lately the alternator belt, I am pleased with the results. Nice quiet purr up to 4,000 rpm and snarls after that to 7k without any problems.

J Lennon

That's great Jeff - and its better to get an opinion like this rather than rely on a forum where people say "they all do that sir" or predict doom and gloom...
Rob Bell

I met Dr Dave at the Balrog's (Tim Guy) technical meet in Dorset last weekend. There was a good show of cars and it was a thoroughly enjoyable day. See and see pics at It's my wishbone with the hold in it!

J Lennon

This thread was discussed between 14/04/2009 and 19/06/2009

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