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MG Midget and Sprite Technical - Sticking Valve?


Well, I got the midget out for the first decent run since the rebuild this weekend, and there are plusses and minuses...

on the plus side, it was fantastic to be out and about with the top down again!

On the minus side...the engine has been off the road for nearly 3 years now, started up about once a fortnight, and moving the car out of the garage onto the driveway, left to tick over a bit and then switched off. So it's not done any significant work in a long time, but has been in once piece all that time. It starts and runs just fine, but starts to develop an intermittent missfire. Pulls great when running well and reasonably well even when misfiring. This gets progressively worse until I'm running on three cylinders. Also starts to get hot, with the overflow tank dropping about a cupful of water through it's overflow when I stop. Strangely though the (new) temperature gauge still reads normal. It sounds to me like a sticking valve, but which is the cause and which the effect? I wonder if the cooling system could be airlocked and hence overheating and causing the valve to stick? Or is a sticking valve causing the overheating?

On the plus side, the rebuilt suspension feels fantastic, the whole car feels tight and handles brilliantly.

On the minus side, the brakes don't feel all that great, they seem to lack bite and feel nowhere near as good as I remember them. Bearing in mind the parts have also been sat for three years, can I simply clean them up with some brake cleaner or would new pads and/or rotors be required?

On the plus side, the bullet mirrors look awesome but on the minus side are useless for actually seeing behind me!!


As ever, all pearls of wisdom will be put to good use.
Thanks in advance.

Mark
MarkH1

'overflow tank' - the header tank should never be filled more than halfway, preferably a bit lower. Fill the cooling system via the bung on the rad. If the nasty black plastic bung is iffy I'll send you a proper brass one ! If you jack up the front offside by a couple of inches that filler hole becomes the highest point so should avoid airlocks.
What do the plugs look like after a run when you've had this misfire?
Brakes - can you lock them up if you stamp on them at 30mph? Are the discs clean and smooth? Is the pedal spongy? Are the rears adjusted up 'just dragging'? I do mine until the wheel is locked then back one click.
David (davidDOTsmithAT stonesDOTcom)

3 years...Id be tempted to give it good make over, the complete works...

all fluid changed, oil, coolent, brakes, ect, hoses and belts, cap, rotors, plugs, wires, points, all filters, a good carbs teardown and cleaning, fuel pump teardown clean and check out, a good clean up and relube of the dissy, freash oil or grease in the rack, ect.ect.

Granted,,,you dont have to, but its an easy way to avoid "chasing the tail" which can be vary frustrating


Prop
Prop

on the over heating.. my fear is the rad and heater core my need a good boiling out...they can really pack up if sat for long periods...esp. heater cores, it seems I always have to flush mine in the late fall.

Prop
Prop

Prop this is a bare shell rebuild so most components will have been checked and/or renewed during the build...
David (davidDOTsmithAT stonesDOTcom)

Ah,

I didnt realise, sorry about that.

Prop
Prop

yeah,

there are always bugs to work out after a rebuild, it seems mine have found a comfortable home in which to live. Keep at them.

Prop
Prop

Does the rev counter needle flicker when it misfires? - indicates an electrical fault.
Are the tappets correctly set - if they are too tight this can result in sticking valves and a gradual dropping off of power.
Guy Weller

Re the bullet mirrors Mark, get a freelander door mirror refill, clean off the tape on the back and take it to your local glass cutter along with the lens from one of the bullets. Ask him to cut two of them from the freelander mirror, cost me a fiver and works a treat :)
Graham.
Graham P 1330 Frogeye

I've always been advised to refill the system from the top hose on the heater, being the highest point, to avoid airlocks. I recently had the car ticking over whilst checking a temperature gauge, which refused to move more than 5mm from the start point. I foolishly let it run far too long - I knew in my mind that the gauge must be faulty, but as it was the second one I had tried ( the first was faulty as well !), I let things run on, not helped by the fact I don't have a standard fan fitted, and I didn't flick the electric fan switch ( coz I wanted the temp to rise to test the gauge !!) Next thing I know we have a lovely rubber smell and the experience known as "kettling". That certainly got rid of a load of rusty brown water ! Flushed the system through later on until it came out lovely and clear.
I wouldn't recommend boiling the engine as a way of cleaning the system however. There can be more serious repercussions.
Geoff Mears (1970 Midget)

This thread was discussed between 08/06/2009 and 09/06/2009

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.