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MG Midget and Sprite Technical - Midget woes. Head Gasket?

Hi,

After finally replacing the engine mounts to the midget today, I drove it down the drive to discover power is really lacking. As in really lacking! Revs freely, however probably 20mph is max. This was why it was originally taken of the road last year - went around a corner and experienced a total loss of power.

Also experienced a misfire. The midget has new HT leads, rotor arm, dist cap, spark plugs, and the carb has been all cleaned up.

Any ideas on problems. I thought maybe the head gasket? But I'm new to all this engine stuff. I've worked on cars for years but in a casual DIY way, brakes, carbs, bodywork, electics. Never the engine internals.

If it is the head gasket, are they easy to change? The Haynes manual seems to suggest it can be done with the engine in place - which is good as I don't have a crane.

Many thanks

Mat
M Andrews

I forgot to say. I checked under the oil cap - there is no white gunge there...but the engine probably hasn't been run long enough for it to collect.
M Andrews

Are you sure the plug leads are routed correctly? This is surprisingly easy to get wrong. Ask me how I know...

-:G:-
Gryf Ketcherside

Yeap. Plugs are all routed as they were before. I've always only ever unplugged one lead at a time. When she was on the road, all power was lost suddenly as she was being driven down the road. I've some though the following;

Removing one lead at a time to iscole plugs/piston issues.

Replacement of leads/spark plugs/cap/rotor arm.

She starts up fine.
M Andrews

Matt,
Some things go "out of tune" gradually. Things like fuel mixture settings, air leaks, points gap. But fewer things actually fail suddenly, when you are going along, particularly if yoyu were only travelling slowly. Given what you have said, and what you have already replaced, then I would suspect the timing might have slipped. Hve you the means to check the setting with a strobe? If not, perhaps you have a radio? Timing can be set sufficiently accurately with that.

Guy
Guy Weller





guy;
Being a newbie I have never heard of using a radio to time an engine. Please elaborate.
Sandy
Sandy Sanders

>>> Please elaborate. <<<

Yeah, I'd like to hear that one myself! Guy???

-:G:-
Gryf Ketcherside

Matt. I do not know about using a radio to time the engine, but do agree with Guy that a sudden loss of power can happen when the distributor shifts its position. Hence, a check of the ignition timing would be an excellent first step. If you are not familiar with the process, there is a technical article on it on my website, www.custompistols.com/ under the MG section.

Loss of the ground strap can also cause such a problem while running. But, when that happens, there is not sufficient grounding capability to crank the engine over on the starter (high battery drain condition). Since your car starts by turning the engine over on the starter, the ignition timing would be the first thing to check out.

To this end, what distributor are you running and do you have points or one of the aftermarket electronic points replacement systems? If a points replacement system, they have been known to go bad, suddenly, and it might be worth considering in your troubleshooting.

Les
Les Bengtson

I'll check the distributor and timing - certainly easier than the head gasket!

As far as I know, this car is all original...certainly its using a condensor and points.

Your site does seem a wealth of information. Thanks
M Andrews

The radio technique has been discussed here before. The idea is that the spark caused by opening the points will actually broadcast over a fairly wide spectrum of frequencies. Obviously, it is only good for static timing, but that was all we used to have when I was growing up.
David "younger than Marconi" Lieb
David Lieb

David has it.
Set the contact breaker gap as normal. Slacken the dizzy clamping bolt so you can just turn the dizzy. Remove the distributor cap and pull it well clear of the dizzy body. Turn the engine forwards until the timing marks are aligned for the "static" setting for your engine. Switch on the radio, and tune it "off station" with the volume adjusted as high as you can with just a hiss. Turn on the ignition and then carefully turn the dizzy body back and forth and listen for the radio to "click" as the spark jumps. This will enable you to pretty accurately determine the correct dizzy position for correct static timing at which point you re-tighten the dizzy clamp bolt.
This setting may not be the optimum for power, but should be reasonably close and will certainly be good enough to get the engine running and performing reasonably well.
Guy Weller

Have you done a compression check....you said this is an on going problem from last year....Im wondering about out of adjustment, worn, or sticky valves....but 1st check, the other things listed above 1st.


after you get the engne warmed up, pull the rad. cap...(plug)...and see if there is any foam in the rad.---that will indecate a blown HG....after its warmed up do you have a lot of white (smoke) at the tail pipe and water flowing out as well = HG failure


prop
Prop

Hey that "radio" technique sounds pretty handy. Certainly could be a useful idea if ever stuck on the roadside with limited tools at hand just to get in the ballpark! Love ideas like that!
Matthew
M Moment

Matthew. Here in the US, a simple test light can be purchased for about $2 and I have one in the tool boxes in each car. It can be used to set the static timing as well as on the road troubleshooting of any electrical system. If they are as inexpensive in the UK as they are here, I would recommend everyone carry one in their tool box. Saved me calling a tow truck several times in the past.

Prop has a good point. A compression check is, always, in order. I do one each time I do a basic tune up and keep the results in a notebook. It allows you to watch for changes which have developed and catch problems before they might leave you stranded. Low compression on cylinders two and three can indicate a head gasket that is beginning to go out, allowing you to change out the head gasket before it becomes a problem.

You mention that you believe the spark plug connections are in the correct order. I would, however, as a favor to me, ask that when you check the timing, the first thing you do is to make sure that the connection to number one cylinder is in about the 2 O'clock position, the connection to the left is to the number three cylinder, the one below it is to the number four cylinder and the remaining connection goes to number two cylinder. Also, make sure that all of the leads are firmly connected to the distributor cap and that the cap and rotor are in good condition.

My daughter's car failed emissions inspection and she brought it up to leave with me to check out. When I had time, I drove it over to a friend who has the emissions test gear to set the mixture properly. I notices a severe miss when the engine was cold. We hooked an engine analyzer up to it which told us that number two cylinder was not firing. Pulled the plug and ran a compression check--good. As my friend went to reattach the spark plug lead, the end at the distributor cap pulled away--it was not fully seated and was not making good contact. Her car, after having the ignition leads firmly seated and minor mixture adjustments made, passed emissions testing with no problems. But, she had been without the car for three months because she could not get it to pass emissions testing and had to get a special, temporary license plate to bring it up to me.

Sometimes, it is the simple, easy to correct things--the things we usually check last. Now, I check them first.

Good luck with the project and let us know what happens.

Les
Les Bengtson

Les:
Point well taken (with embarasment).

Matthew
M Moment

Mat,
to part of your original question, if you ever need a head gasket, yes you can do it with the engine in the car. and, it really isnt too bad of a job, especially if you do it 3 times in 3 weeks. as Gryf would say, ask me how i know....

Don
don g

As above with dissy/points checking.

Also - did the throttle cable slip (ie. does pressing the accel cause the throttle spindle to rotate 90 degress / quarter turn)?

Check the fuel pump working; check flo-jet and main jet not blocked / sticking.

As Guy says, you don't adjust out a failure somewhere in the fuel and sparks.

BTW - compression test on all 4 cyls will take <15 mins and will tell you if you have a head-gasket fail.

A
Anthony

"Revs freely, however probably 20mph is max"

"went around a corner and experienced a total loss of power"

"I've worked on cars for years but in a casual DIY way, brakes, carbs, bodywork, electics"

"Replacement of leads/spark plugs/cap/rotor arm".

"She starts up fine"

I wonder, clutch slip, driven plate loose?

Regards
Roger
Roger T

Many thanks roger. more ideas to go on - appreciated.

the clutch seems good though. The engine is unknown to be, its reconditioned (don't know to what standard mind!). It does seems to have a oil leak - so I'll probably give it a good looking over. Head gasket, de-coke, piston rings. My first adventure into the workings of an engine - a BIG challenge yes! But I want it all done correctly.

All in the car at the moment, but I'll probably remove it the end of the year to tart the engine bay up. I'm looking to respray the midget from yellow to red. A big job! Also replace the oil seal between the engine and gearbox.

I'm wondering, it is worth getting an oil cooler?

Many thanks
M Andrews

Why do you need an oil cooler?

A
Anthony

I don't need an oil cooler even at 35+º in Le Mans

We don't seem to know which engine you have Matt

If it's an A series you don't have a physical oil seal at the back of the engine, unless a kindly previous owner has fitted a special kit to the car in a previous life. Oil is "controlled" by a rotating "Scroll seal" engineered on the crankshaft which is supposed to rotate and slip oil back inside the engine as it is a reversed Archimedes screw designed-ish to overcome the oil's tendency to obey pressure and gravity to search out the garage floor.

You say it does have an oil leak, if that is at the back of the engine clutch slip is quite likely...
Bill

Sorry Bill, your right. Its a Mk4 midget, the 1500 triumph engine. If no oil cooler is needed in Le Mans - good old blighty should be OK without.

Thanks for the tip, I'll endevour to find out where the leak is from.

If i do attempt the head gasket change - is there anything I should be wary about - it will be a first for me. Never so much taken the rocker cover off.
M Andrews

if you got the 1500, you dont have to worry about having a scroll seal.


someone else just went thur this about a month ago, and it was a blown Head gasket with a 1500

WAS It Bob T. I cant remember

prop
Prop

An oil cooler is definately a good idea with a 1500, try and get one with a thermostat in the take off plate. While you are at it fit the extra oil feed pipe to the cylinder head, see photo(available from Moss) well worth it I feel.

Carl


C Bintcliffe

This thread was discussed between 04/04/2008 and 09/04/2008

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