16 replies to this topic

[haggisfrog]

Hi, I have an MPi with shot valve stem seals. I'm almost using as much oil as petrol .o) The car didn't run for almost 5 years so the seals must have stuck to the stems and dried out.
I have the seals and a gasket set. But if I can avoid taking the head off, i'd love to. I have heard that in some cars, you take the piston down a couple of cms below tdc then feed the end of a ball of string in through the spark plug hole and fill up the gap between the piston and head. After bringing the piston up as much as possible, you can compress the valve spring - the valve being held in place by compressed string.... Obviously a conventional spring compressor is out, you'd need something which could use the fixings of the rocker gear.

Has anyone tried this technique on an A series? I'd be interested to know if it would work. If not, I'll have a crack and let you know!

[Mini-Mad-Craig]

Why would you want to avoid taking the head off?

[haggisfrog]

ermm- a couple of reasons. Time saving, don't have a torque wrench, don't have to drain the coolant, also, saves a head gasket (i can live with the cost but its just an added benefit)
Also, I'm a bit scared of MPi when I look at all the potential problems if any of the multiple MPi related hoses split when removing giving rise to air leaks and really awkward to find issues. The less I dismantle the better. I'm in France and no one but no one knows how to diag and repair an MPI so if I break it, I'm on my own....
That just about sums it up.

[mattbeddow]

You dont have to drain the coolant to take the head off, least i didnt with my a+
And i would seriously consider doing the job properly by taking the head off and using the correct tools, it just takes 1 valve going wrong by your method and you have to revert to removing the head.

As for not having a torque wrench, id strongly suggest getting one. theyre not massivley expensive and almost every job on a mini requires one

Also just remebered that to take the valves appart by your method, you will need to remove the rockers, so will need a torque wrench to put them back on anyway and the rocker pedistals share some of the studs with the head

Edited by mattbeddow, 21 March 2013 - 03:14 PM.

[haggisfrog]

Forgot about the rocker sharing the cyl head blots.... You're quite right, could create gasket issues anyway. Ok, advice taken, I'll do the job right )
I'll make the most of the job and regrind the valves.

Thanks for the help

[mini-luke]

You'll probably need the valve guides replacing too

[Ethel]

There is a trick of stuffing the cylinder with cord (rope) through the spark plug hole to keep the valve from dropping, but I'd agree that if you need new seals it's probably worth doing some other head maintenance too.

[Cooperman]

IIIIf it is burning that much oil then it's possible it could be piston rings and bore wear that is causing the high consumption. Before taking the head off, run the engine at about 1000 rpm, take off the oil filler cap and see if it is 'chuffing' smoke out the filler hole. If it is, then it's a bore wear issue.

[M30]

I've done this job in the past on a Sierra with the 1.8 cvh engine. I did it by drilling out an old spark plug and welding an airline fitting to it. I then pressurised each cylinder in turn which holds the valves closed while I removed the collets, spring and seal. Tricky but can be done

Stu

[KernowCooper]

There is a special tool which screws in the plug hole and has a offset leg on it to hold the valve up, I used to work with a mechanic Rob Andrew (RIP Mate) who could change springs on a mini and new stem seals in his dinner hour using that method.

[lrostoke]

Just a thought if you backed the tappet adjusting screw right off wonder if you could get the valve cap and spring out with out removing the rocker assy ??

If you really didn't want to remove the head !!!

[skoughi]

Take out a spark plug and gently poke in a ballon and blow it up then tie it off! Heard this story but have never believed it!!

[midridge2]

how will you compress the spring to take the collets and cap off, a standard spring compressor will not work but i believe you can get a special tool to compress the springs with the head on.

[tiger99]

The "special tool" is just a long forked lever, possibly made by butchering a tyre lever. The end engages under a nut fitted to a rocker stud, and the slot passes over the valve stem when you push the free end downwards. It isn't going to be of much use on a Mini, because you can't create a fulcrum for it without removing the rocker gear, which involves undoing some of the head studs, but it does work on some cars, with either the compressed air in cylinder or rope trick.

You could attach a strip of metal or piece of chain to a manifold stud, to provide a fulcrum, but if you are taking the manifold off you may as well have the head off.

I don't know much about MPi's, but despite the extra plumbing etc I would still do it the normal way by taking the head off. I like to devise shortcuts for doing things, but in this case it just isn't feasible.

[Carlos W]

lap the valves in and a bit of a decoke whilst youre on