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MG Midget and Sprite Technical - MG Midget 1500 1974 engine knocking

Hi
I have an mg midget 1500 1974.
Getting knocking noise from engine.
So rebuild cylinder head and a new camshaft, but the noise is still there.
Any ideas what it could be.
Have not taken out pistons or done bottom end.
Regards tony
A romita

What's the oil pressure like?

Dave O'Neill 2

Yeah ... a few more details will be needed

Oil pressure both at tick over and warmed up at normal operating temp at idle (1000 1200) rpm would be great

That said... one of the common weakness with the 1500 are the thrust washers wear out fairly fast, but it's not a big deal to replace them if that's the cause... and i stress the word ""IF"" as we don't have enough info to help out properly

Prop
1 Paper

Hello
When engine is cold got around 40 psi have not tried it when warm as afraid of more damage. It's really loud.
I remember end of summer last year I was out with the mg and was knocking but only had half a mile to get home, she lost power almost crawling. But could be due to cylinder head value was broken. Head has been done.

Regards Tony
A romita

Knocking is usually associated with worn big ends or more rarely with worn little ends. When you had the head off what was the state of each bore?
If the thrusts have gone you would feel a lot of fore and aft movement of the crank. In cases of severe thrust wear the thrust bearing can rotate out and end up in the sump.

On a 1500 you can take the sump off with the engine in place so you can change big end bearings. With the head off you can take out pistons and con rods as well.

Did the knocking happen all of a sudden? Or had it been noticeable all the way during the run?

Rob
MG Moneypit

She was running ok. So suddenly it started.
When head was off the cylinders where really good no scoring or marks.
Think it could be big ends aswell.
A romita

Or the timing is out
A romita

When its big ends, the noise is usually at its worst on initial start up when oil pressure hasn't built. Then depending on how bad they are, it will quieten down slightly after a moment or two.
GuyW

No it stays the noise.
A romita

I am only meaning a dfference between the first 20 seconds or so of running. Butif big-ends are already bad, rather than just beginng to wear, then the noise doesn't quieten down much at all between start up and runnig. Have you checked the crankshaft for fore and aft movement.? Its an easy visual check.
GuyW

Ja there is play, thrust washers are worn.can they be changed with crankshaft in car.
A romita

Yes.
What I would suggest is that you take the sump off and have a look . Worn thriust washers are unlikely to be the cause of the knocking noise, but if they are worn then the big end and possibly the main bearings are very likely to be worn as well. And that would certainly tie in with your knocking noise.

When the sump is off remove one of the big end caps and take a look at the bearing shell - #3 is a good one as it often wears faster than the others. A worn bearing will show up immediately. If its very worn then the steel backing or the copper layer will show. If only slightly worn you may get away with just fitting new bearing shells but that will depend on the state of the crankshaft. If the crankshaft is worn or damaged then the engine would need to come out for a full strip-down, crank regrind and rebuild.

GuyW

I would do what Guy says now. If it is the bearing shells you need to know before it’s made worse.
Dave Squire

Ok. Look tomorrow. Today took the timing chain cover off again, but it's all ok.
Thanks guy's.
A romita

40 psi at cold sounds quite low for a 1500. How many miles on your engine?

From what I read, it sounds like a main bearing in the engine. As has been mentioned, you can get at the bearings from under the engine. The front bearing cannot be changed with the engine in the car.

I think, once you have determined the actual problem is to pull the engine and rebuild the bottom end. If the cylinder walls are in really good shape, you may not have to do anything to them. However, in for a penny, in for a pound when it comes to rebuilding, may as well do the whole thing right the first time.

Good luck,
Clare
Clare Ravenwood

Noises are always difficult to describe to others, and therefore to diagnose via messages! I know exactly what a worn 1500 big end sounds like, but that may be qite different to what you are hearing! So I may be misleading you, but a visual inspection would confirm.

The other thing that may often help to pin-point the problem is a mechanic's stethoscope. Or if you don't have one then something like a long large screwdriver or metal rod. You hold the handle end against your ear (better still, against the bony bit imediately behind your ear) and then probe around with the end of the screwdriver blade touching onto various areas where the noise might be originating from. With the engine running of course, but beware of catching moving parts!

If it is worn big ends you really don't want to be running it for more than a few minutes at low revs to do these checks or it will damage further.

PS.Main bearings give a steady rumble; big ends give a distinctive knock; piston slap is more clacketty in sound
Check there are no leaks around the exhaust manifold. It is surprising what heavy sounding banging noises this can make.
GuyW

Guy beat me to 1 of 2 thoughts i have,

Yepp... check for exhauste leaks esp around the exhaust manifold... loose hardware or holes

My 2nd thought i have is because the knock started suddenly, and you still have 40 psi on start up at around 1200 rpm ... which I think is really good... but I don't know squat about 1500s

Spun bearing... Its where the bearing shell spins inside the main or big end

Btw... what happened that you broke a valve in the fly head... not being critical or judgemental just an interesting comment that could be related


Another thought... try taking the rotating achiallies off the engine (not off but inactive) fan blade, water pump, altenator, air pump ECT ECT


And a bonus last thought... pull the plug leads one at a time then back on, and see if that has any effect the sound of the knocking


If you drop the sump pan... collect the oil and look it over for bronze or copper or other ooper metal
1 Paper

Ha ha Prop! And you beat me to it too! Taking the fan belt off to cut down on engine noise, making it easier to listen and to eliminate the possibility that the noise is coming from one of the ancilliaries is one of my favourite tips! Only I forgot to mention it this time. LOL
GuyW

Alot to test then.
Had the sum off last week and cleaned it out, did not find any metal or so was , just a lot of slum , think it was never off engine hast only 40,000 miles.
But will check old oil again tomorrow.

What if the oil channels are blocked, would that cause knocking?.

Thanks again
Tony
A romita

That was probably the ground down white metal bearing surfaces. Look at the inside of #3 big end shell asap. Make sure you know exactly which bolt goes where and which way around the cap goes for reassembly.
Dave Squire

Number 3 is at back of engine or
A romita

Number 1 is at the front, number 4 is at the back.
Malcolm Le Chevalier

Must reground and rebuild of engine and looks like 1 or 2 new rods.
Not good. So engine out.
A romita

Tony, what is wrong with the rods?
GuyW

The rod 1 or 2 are so bad from the bearings. Have only 7 pieces of bearings and not 8. Think it did eat one or 2 up.
Sh*t
A romita

Engine is out


A romita

What are we looking at in the photo... obviously it has been savaged

Any ideas what the cause of the problem is ?

And how are the connecting rods bad... to piggy back onto Guys question

At least you made some serious headway

Prop
1 Paper

Looking at 1 of the bearings on 1 rod only found 1 bearing the other bearing was eating away. Cause I do not know just got engine out yesterday and I stopped there,
I will start to strip her today after a good cleanING of engine and gearbox. Think 2 connecting rods will need replacing. Scored.
A romita

Is that the outer face of the bearing? Has it spun the bearing?

Looks a mess.
Malcolm Le Chevalier

If it's eaten away a complete bearing shell it must have been making a noise for quite a while. Or driven after the bearing had more or less fused itself to the crank. I guess the crank must be in a mess by now too.
GuyW

If one of the bearings is eaten away esp after 40,000 miles ... I wonder if the engine is even rebuildable

Can a 1500 crank journal's even be turned beyond. 060


I'm looking forward to your analyzes as to what caused the damage
1 Paper

Yes. Think it did spin.
But as soon as I heard the knocking last year I took it off the road and since then not started engine, so don't know why so bad. Yes crankshaft look horrible.
Think it did spin around.
Rebuild now.
A romita

Are all the bearings damaged? The bearing shells shouldn't turn. Unless the bearing cap is put on backwards in which case the tang faces the wrong way and the shell can then rotate.

Do you know what the history of this car is?
GuyW

Ja the engine was never touched. Just found out that 2 shells where stuck together very thin now.so did not eat 1 half of shell.that was number 4.
A romita

Mg is actually from gosport portsmouth uk with history service. The owner moved to germany then I brought it from him navel man. Now moved back to uk.
A romita

Trevor Jessie had a 1500 spin on him, but that was after he left the BBS.... SO it can happen but no idea as to why

Prop
1 Paper

Prop, 40 psi for a 1500 at cold start seemed very low to me. I think that as the engine got hot, oil pressure dropped very, very low and lack of lubrication caused the bearing to seize to the crank and get spun accordingly.

Clare
Clare Ravenwood

Anyone know what I can do so it gets more oil. Did see a video in youtube that they did drill oil channels larger.
A romita

Video might be this one from John Twist -

206 MG Midget 1500 Engine Walk-through - https://www.youtube.com/watch?v=uAgbcbxFD98

Nigel Atkins

Tony,
The standard engine is pretty well designed as far as oil ways. Think hard and check advice from more than one source before you start to alter things like oilways. Enlarging one oilway will increase flow but inevitably reduce the pressure supplied to other components so only make small changes to oilway diameters. There are sometimes problems with oil feed to the big end bearings 2 and 3 which is why I earlier said to check #3 first. For this reason some people drill out the oil feed to the centre main bearing, which then feeds on to these two big ends.There is also a higher capacity oil pump available, worth fitting as you will probably be needing a new pump anyway.

The only other poor oil feed that I think 1500s are known for is the feed to the rocker shaft and there is a kit available to provide an additional external feed to correct this.

Very important is to make sure that the oilways are properly cleaned out when you rebuid the engine. Don't assume that the machine shop that does your regrinding will clean out the oilways. You need to check them too!

Used in a warmer climate than the UK - well the summers anyway ! - the 1500 really benefits from having an oil cooler and if it doesn't already have one then this may well have been the original cause of the bearing failures on that engine.

The other thing worth doing if rebuilding this engine is to get the crank and flywheel balanced as a unit. On mine I also had the flywheel lightened a bit which gives a more responsive engine.
GuyW

Good advice there.

Couple of notes, I can remember reading criticism and information (from Deborah Evans) about the oil rocker feed kit that Moss sell.

If an oil cooler is fitted then it also needs an oil stat to control it otherwise the oil can be over cooled which will mean the oil isn't working fully to protect the engine and this could possibly be a lot of times.

The factory didn't fit oil coolers or offer them as an option even to warmer climates, they did have different cooling fans for different markets. Just as it's very important to have the oil ways clear the same applies to the water ways in the engine, rad and heater matrix. As already said these are often forgotten about by workshops and the car owners, possibly for decades.
Nigel Atkins

Probably best to look for a spare engine to rebuild - usually quite a few 1500's about.

IMO an oil cooler is essential on a 1500 in a Midget, engines seem to run hotter in the Midget than say the Spitfire etc - I fitted one when we had a 1500 after replacing the B/E shells which were well worn after less than 40k.
richard b

There is a oil cooler built in my mg midget.
So today did engine bay all done and engine in pieces. Crankshaft is not for reground where the shells spun is a hole or its collected the metal. All others are good
Have not decided on what I am going to do now with engine.
A romita

The cooler can hold a lot of crud after a blow up - so will need careful cleaning or replacement to avoid damage to rebuilt engine.
richard b

Tony,
if you already have an oil cooler and are going to keep or replace it you'd be best to add an oil stat to it so that, like the "water" side with the "water" stat, it isn't getting cooled unnecessarily.

The oil stat will also help warm up your engine and the engine oil quicker from cold starts which is what you want.

An oil cooler also doesn't drain on oil changes which again isn't best.
Nigel Atkins

If l was spending a lot of time and money on rebuilding a nicely prepared engine l wouldn't use an oil cooler that had been on a damaged engine like that. I would buy a new one.

When I had my 1500 I used to replace the big end shells as a routine maintenance job, every 25,000 miles and never had to have the crank reground. For those shells to get thin enough for one to slide over the other they must have been badly worn and must have been making a lot of noise.

If the crank is now also damaged I would look for a complete replacement engine as the 1500 engines are still plentiful and cheap. Or l would take the opportunity to fit a K series. It's the ideal excuse!
GuyW

Guy...

Or a climax engine..... deb Evans loved those engines big time in the 1500

If your going to do the 1500... I'd go a head and drop in a spjtfire 5 speed electric overdrive granny

Just a thought

Prop
1 Paper

what is a "5 speed electric overdrive granny" Prop!
GuyW

Hey guys
Thanks for all your feedback and ideas for the rebuild of my mg midget.
There's alot to think about and yes will be using all new parts as to buying a used engine but found any here yet in Germany.
I am now and again in the UK, could wait and and get one over there , but don't know when I be over again at the moment.

Don't really want a used engine as the engine shell on my mg midget is really good condition, cylinders are A1 and has a new camshaft and head has been rebuild.
A romita

Guy...


Malcolm Le Chevalier

Brilliant! Something to look forward to!
GuyW

"... I wouldn't use an oil cooler that had been on a damaged engine like that. I would buy a new one."

When my 1380 exploded, I didn't even think about trying to salvage the cooler. For what it cost, it was a no-brainer, as they say.
Dave O'Neill 2

No.no
Have already brought a new one.

Good picture malcolm hehe
A romita

I should have said (sh*tfire) haha

Granny is not a bad word for these old " trannys" haba

A British 4/5 speed granny tranny ... haba

You could still get a good 1500, have the lower end remachined and transfer all your new parts over

Getting another 1500 crank and having it all line bored to fit won't cheep

Plus is there any damage to the cly. With the crank spinning on main caps without much bearing shells

Considering you could find a good low milage Ford zetec with 5 speed in the salvage yard is not a bad way to go... just shoe born it in AND not worry about the rebuild

Hook up 4 small carbs and a crank trigger ignition and save some cash and sell your 1500 parts to malc

Prop
1 Paper

Hi
Could the cause be the oil relief pressure valve. It's in a bad state, not usable any more.
Does anyone know if the 1300 and 1500 crankshaft are the same size?
A romita

The 1300 has a shorter stroke.

But there were also too variants of the 1300 crank with very different journal sizes. A later crank (large journal) would fit and turn your engine into a 1300.

An earlier crank I think is pretty rare as they are "the one to have" for Spitfire tuners.
Malcolm Le Chevalier

Hi
Mg midget is up and running 👍👍👍
It's great now.
Just one problem can't seem to get the clutch fluid to come out of bled nipple. No pressure there.
Any ideas.
Tony
A romita

This thread was discussed between 20/01/2018 and 15/02/2018

MG Midget and Sprite Technical index

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