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MG Midget and Sprite Technical - Broken down Sprite

Ok so my 69 Sprite ran beautifully yesterday and flew there the mot -
100 mile later now on my way home from work I've broken down and awaiting the AA

Temp gauge went up high and steam coming from engine bay

Would this be a faulty radiator or thermostat ?

I completely flushed and replaced the coolant a few weeks ago and levels prior to this were fine - also replaced perished hoses and all are still ok

Not had this before so unsure as to what the cause is
richard weaver

Hi Richard, sorry to hear you are having problems.

Check easy things first before thinking the worst!
Assume the water level was correct when you set off, then:
Was the filler cap on tightly?
Check the fan belt is still there to drive water pump?
Check for splits in the hoses - evidence of staining from coolant spraying out?
Check for leaks around loose hose clamps (include the little one between head and water pump, difficult to see)
Any leaks from a split radiator?

If all of the above are OK, then its something deeper.
Thermostat stuck closed.
Leaking heater radiator.
Head gasket failure. :-(
Guy W

back in 1976 on the M4 my midget shed its radiator fan.
The temperature gauge only rose when I left the motorway and slowed down.
happy days
David Cox

Think we have found the culprit

Slack fan belt and split at the backside of the bypass hose water pump to cylinder head
richard weaver

I hope you get lucky and the hose/belt are the only problems.
If you caught it early enough you might just get away without a HGF! But my betting is you'll get another few hundred miles before it does in fact fail.

Hope I'm wrong.

Best of...
M McAndrew

Richard. If you don't mind removing the pump, it's better if you can fit a proper bypass hose rather than the easier convoluted one, given the poor quality of some modern rubber parts. Better still, a silicone one.
Bernie Higginson

Or buy a 1500, none of this constant by pass hose misery to content with :-D

*Runs for cover*

M Le Chevalier

The aa man did a test on the coolant and at this point shows no signs of failure I pulled over whilst it was still creeping up so fingers crossed on that one

I'll have a go at replacing with the correct type of hose
richard weaver

also replaced perished hoses and all are still ok

Something else to check for andnindont know why...but after about 100 miles, I always have to retighten the hose clamps on brand new hoses, of they will leak out all there anti coolant... and fairly fast also

Prop and the Blackhole Midget

Blimey I didn't realise anyone still used bypass hoses. My Metro head has the bypass blanked off and I just have two 1/4" holes in the thermostat. That's how the head came to me (and the one before, but that's another story).
L B Rose

LB - that's all standard on a Metro, that's why it uses a different pump (with no bypass outlet).
David Smith

Well more Sprite problems

Replaced the burst hose but still loosing water and overheating with no obvious leaks - all hoses are fine

Seems there's a slight leak on the head gasket - not a total failure so a drop of water is getting into one bore and increasing compression slightly - cars driving well but loosing water

So gonna have to night the bullet and do my first head gasket change

Will have the head checked and skimmed - any other suggestions or is it just follow the Haynes Manuel ?

richard weaver

As you'll have your valves out for a skim anyway it's a good time to refresh the seats with a little fine paste. Also of course check the stem/guide clearance.

If you're going to clean up the piston tops, turn the pistons up to TDC and push a little grease in the gap between the piston and the bore. Saves any crud going down there and easy to clean up after.

As many have noted recently, the choice of gasket is important. It seems there a lot of rubbishy ones about these days that don't cut the mustard. Payen seems to be a good brand, but I'm sure there are others.

Good luck. It's not a hard job once you're into it.

Oh yes, while I think of it...

After skimming made sure to break any sharp edges round the combustion chambers with a sharp, hard scraper or the engine will detonate. That lesson was 45 years ago, but I haven't forgotten it.

Don't quote me on this but I think if your engine's a 948/1098cc you're able to remove the tappets in situ for a looksee. If the engine is a high-miler and you think it's worth it, of course. Pretty sure you can't do this with a 1275 though. Others hereabouts will know for sure.

It's a 1275 engine - taking it to a very good engine shop who rebuilt my other midget engine and builds a lot of high end motors so il get him to check it all out - I've never actually done any head work so nervous :-)
richard weaver

Okay, that sounds good. In that case it might be worth asking the shop to check/break the sharp edges afterwards, and to check the guide clearances and valve seats too. I'm sure they'd do these as SOP anyway.

While the head's off can I suggest you have a feel of the top surface of the block where the studs screw in to make sure there are no ridges sticking up at the top of the holes. These can prevent the new gasket seating properly, but it's easy to correct by carefully and gently using a countersink. Making sure to stuff the bores with oiled rags first to keep any swarf out.

I've only done one A series HG on my own (sister's 1300 Vanden Plas) but it was dead easy as I recall. Probably easier than yours though, being transverse with easy access. I also measured the studs to see if they had stretched, but they were all within tolerance.

Just as a thought you could ask your friendly engine shop to check your torque wrench for accuracy - a few pounds out either way can make a lot of difference.

Finally - and I apologise if this is really obvious - it's important to make sure all the bits go back where they started from. Valves, pushrods, rocker adjusters, springs, spring seats, caps and collets etc. should all go back in their original positions unless being replaced.

There's some recent stuff in the archive about retorqueing the head. IIRC Peter Burgess made really good comments about this and he REALLY knows his stuff.

Have the head both vacume tested and magnafluxed BEFORE they do any work

Before you take the head in, look between the valve seats and see if you can detect a crack... popular spot for these heads to break

Id also put a flat edge on the head surface to see if its flat

Is there any coolant in your oil sump pan or oil in your radiator

Prop and the Blackhole Midget

All this long list of things to do is all well and correct. But being a lazy optimist l would just whip the head off, clean the head and block surfaces and whack it back together again with a nice new Payen gasket.

I do take care to torque it accurately - especially not to overtightened it which transfets the tension off the fire rings where it is needed, and onto the flat bits of the gasket where it is less important. Adjust the valves, refill the fluids and off you go! Can all be done comfortably within an hour.
Guy W

Im with Guy!
Steven Devine

But being a lazy optimist l would just whip the head off,
.............well, let's see now

disconnect the battery
drain the coolant
remove the rocker cover
remove spark plugs
remove the air filters
disconnect the throttle and choke cables
remove the carbs
remove the inlet manifold
support the exhaust pipe
remove the exhaust manifold
carefully release cylinder head bolts
try and remove cylinder head
try and remove cylinder head again
finally release cylinder head
clean cylinder head - 15 mins
clean block face - 20 mins
fit new gasket and replace all the above
plus re-set tappets

" Can all be done comfortably within an hour" ..hmm?

M J Chapman

Yes it can. Maybe I don't apply the "Carefully" stages that you list! But you are just creating quite unnecessary work for yourself!

I don't disconnect all the carb stuff, I undo the 6 manifold nuts, but leave carbs, exhaust, air filters, choke, throttle and fuel lines all attached and just ease it all back an inch or so out of the way.
I have one of those battery isolators so that is just a switch to spin off.

Why take the spark plugs out? If you leave them in a quick spin of the motor and the compression lifts the head so it comes off easily!

You did however forget to list:
Disconnect rad top hose from thermostat housing
Disconnect block to water pump hose - assuming you have one (I don't)
Disconnect heater hose from heater tap
Disconnect temp gauge probe.
- - - Probably why it takes you so long to remove the cylinder head ! ;-)

Guy W

I would change the following steps

>remove the air filters
disconnect the throttle and choke cables
remove the carbs
remove the inlet manifold<

to >remove the carb assembly<

That way you save time and don't have to reset everything. That's the way I've always done it even though it is a bit of a fiddle to get the center most nuts off of the head, in the long run it does save work and fewer gasket surfaces to clean off. Once you've undone the nuts you just lay the assembly on the foot well. And you shouldn't really have to disconnect the exhaust manifold from the pipe. Just slide it sideways.
Martin Washington

I agree - the job can be done in an hour or so if the car is used to coming apart and you know your spanners, angles, shortcuts etc. Surely Option 1 is the quick fix - for the price of a gasket its got to be worth a try before you resort to machining etc
S G Macfarlane

I'm with Guy. The car was ok before it started losing water. Hence why would it need a skim or guides or seats cut bla bla?

Sussex sells a HG set for circa 10 quid. And YES, they are ok. I've used them. I have one the Midget, and one on the engine in my Sprite.

For 10 quid, I'd pull the head, clean it up and bung it back on. But as a quick check before bunging it back on, I'd invert the head, -- PLUGS STILL IN -- fill the comp' chambers with petrol, and see if it leaks away. If not your good to go. If it leaks, do a quick grind.

Creating lists makes it look like a lot of work, when in reality it's not.

If you were closer Richard, I'd do it for you, simply because it's so easy, and not that time consuming.
Lawrence Slater

PS. If you still have the standard exhaust manifold, leave it connected to the head. And in any event I wouldn't take the carbs off the inlet. No need.
Lawrence Slater

Well, fair comment. It never occurred to me to disconnect the whole breathing apparatus in one go.
I'd be interested though as to how you re-fit the centre manifold nut.
Still, for someone like the OP on his first attempt to remove the cylinder head, in my opinion, one hour is very optimistic.
M J Chapman

One huge glaring differnace between guys list and MJ list

Beer ! No mention of beer time outs, and the time involved for that mandatory part of the process

Im in the camp, if your going to go to that much trouble to pull the head, then go all in and get the valves reground and guilds checked ect ect. As it just saves time and hassle in the long run...sort of like the bath tub faucet cartridge, if the hot water cartridge goes bad, I do the cold water also at the same time, if the right headlight bulb burns out, ill also replace the left...cause it wont belong before it blows

It just seems to be easier to wipe out several potential up coming issues at one time and just be done with the hassle of it all
Prop and the Blackhole Midget

Coffee and tea, Prop. You approach is sensible but not what l would choose to do. As soon as you start adding valve grinding, magnaflux etc you immediately change what can be a quick 1 hour job into several days at the very least. In your case l seem to recall it became many months ;-) Once you deliver the head to the specialist you then wait your turn in their work programme, over which you have little or no control.

I prefer to take the slight gamble that the 1 hour job entails, but have a good chance of it working and being back on the road later the same day.
Probably comes from years of use when my Sprite was my only transport. I do run a couple of quick checks with a straight edge and flashlight, and the valve leakage test that Alf describes which can be done in a matter of minutes.

As forbeer time - if you get aove on and do it in double quick time then you can have the beer or two afterwards as a reward!
Guy W

Alf? Ha ha. I almost searched the posts to see who that was. LOL.
Lawrence Slater

;-) just teasing. I considered saying Jennifer but though a more attractive thought, its not as funny.
Guy W

Months ?? Huh, come on , no need for exaggeration.... it was years !

You do have a point, for no more then it takes to pull the heads you are ahead with just changing the gasket and go, if it is deeper you have only lost a day or so and you can always try agian, with my toyota head I wouldnt try that because of the amount of time involved

I guess it comes back to that right tool for the job and fix it right the 1st time that I tend to be addicted to unless im in an expermential frame of mind
Prop and the Blackhole Midget

Prop, I genuinely have always taken it that your mind was experimental!
Guy W

As in FrankenProp Guy? ;)
Lawrence Slater

Its always on full tilt....haha,

but in the end I got the head I always wanted
Prop and the Blackhole Midget

Jennifer Guy? Now that has lost me. Lopez? Saunders? lol
Lawrence Slater

Jennifer Lawrence, Lawrence ! Easier on the eye than Alf.

I think this thread has drifted.
Guy W

I'd never heard of her until you explained. I googled her though. Has she got a Spridget? ;)
Lawrence Slater

This thread was discussed between 22/10/2015 and 11/11/2015

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