MG MIDGET ENGINE NOISE (link to recording of engine sound)


#1

My 1979 Midget engine is making a tapping sound. I’ve recorded it and uploaded it to this folder:
https://drive.google.com/open?id=0Bxi7AC7gwFMMSFdFOEpBRzA5dkU

Do you know what it is?

Thanks for listening!


#2

Sure can’t tell but it sound like either valve tappet noise or something hitting something else like a fan blade. It should be fairly easy for someone to just take a look at identify where it is coming from. Don’t know enough about them but it sure sounds like a fan blade or something is hitting the radiator or something. I don’t know if it should be driven.


#3

I can’t tell either. I’ll suggest that the spark plugs be removed and the engine cranked over while listening closely. At a slower RPM the noise might be easier to isolate and if the noise is compression related it will be significantly reduced if not eliminated.


#4

It is a simple little engine. Pull the valve cover and look inside. If you are lucky it is a broken pushrod or rocker arm. Easily fixed. If you are not lucky, a connecting rod is about to break loose poke out the side of the engine block.


#5

Sounds valve related to me. Never worked on a MG but with valve cover off you may be able to see what is making the noise. If not hold the gead of a ball peen hammer in one hand and push down on the pushrod end of each rocker with the handle while the engine is running. If the sound changes that is the problem. Could be as simple as a valve adjustment.


#6

First off, make sure the oil level is at the full mark on the dipstick, and the oil is clean. If that’s ok, use a length of garden hose as a stethoscope to try to isolate where the sound is coming from. If it seems to be coming from the top of the engine, schedule a valve adjustment procedure with your shop. That may not fix it, but it will probably turn up what’s causing the noise in the process if it isn’t just a simple adjustment problem.


#7

As mustang said, it’s a simple little engine. I happen to love Midgets.

And as such, it’s subject after 38 years to wear, and that includes what I call “tiredness”. Lifters wear, rockers wear, valves wear, valve spring become tired, and all that stuff. My suggestion would be to start by pulling the valvecover and checking the valvelash. Be advised that the valvesprings may have lost their springiness and it may be necessary to have the springs tested by a machine shop that does engines. Before trying this, make sure you have a manual and the tools necessary to do the work. It’s a very simple engine to work on, but you should never start working on any engine until you’ve obtained a good manual and familiarized yourself with the process you’re about to undertake.

And I have great news. These cars have a cult following, and parts and manuals are still readily available for them.


#8

Is the noise the same right from the start or is it increasing as the engine heats up?

It could be a bent rocker arm, but I haven’t seen one bent or damaged on any of these A-series engines ever in 40+ years, but I have not seen them all so it could be and it is easy to find out.

Depending on the year, You should have an oil pressure gauge in the dash. What are the readings if You have one at idle and at 3000 rpm.?

My fear is, that a rod bearing has gone south. I’ve had a few of them in my shop and they sounded like Yours and the readings on the gauges was low too.

Those engines will last a very long time if treated well and that includes using 20W-50 oil. That’s what the book says and that’s what the engine wants, even in these days with high quality oils. Been there, tried that.

Ahh, not until now I noticed its a -79. That year should be a 1500 cc engine, which is a Triump engine. I don’t know anything about those, but the guys next door are into Spitfires, so I can ask them next time they show up. Please confirm year and type of engine and pressure readings.


#9

Being as I’m deaf in one ear and don’t hear too well out of the other I decided not to mention my suspicion that the noise was possibly an exhaust leak but maybe someone with 20/20 hearing felt likewise.


#10

My first question is, has the engine been overhauled or rebuilt recently? The reason I ask that is first, I believe the sound is a loose tappet and when overhauled or rebuilt, sometimes the cam is reground to produce the original lift and duration, or reground for higher lift and duration in order to increase performance.

The cams in these engines were made from mild steel and case hardened after grinding. Most rebuilders today are used to cams made from a harder steel and are not case hardened. If a cam that was case hardened is reground and not case hardened after, it will be very soft and wear down very quickly.

If it has not been overhauled, rebuilt or just had the cam reground for performance reasons, then it is likely that it just needs a valve adjustment, which on this engine is very easy to do. You can get a Chiltons or Haynes manual for this car and a few basic tools and do it your self quite easily. These usually require frequent valve adjustments.

Edit: @Rod_Knox could be right also. If he is, then it would be most likely the exhaust manifold gasket as it sounds like it is caused by one cylinder. An exhaust leak at the donut (manifold to exhaust pipe gasket) would be 4x faster.


#11

I don’t know the engine history. I bought the car 2 years ago and most of the time it has been sitting. The odometer reads under 40,000 claimed to be original.


#12

It’s a 1979 MG MIDGET 1500cc engine. Odometer approx 39,000. It doesn’t have an oil pressure gauge. I read about the oil and am aware of 20W-50 and the presence of zinc. I have not use the car much. I’d like to use it more, but I’m not going to drive it with this new tapping noise.


#13

I’m back again, I’ve talked to the Spitfire guys today. We have listened to the noise several times and it’s not fatal in our opinion. A mechanic have to take the valve cover off and thoroughly inspect the valve train for a bent push rod, bent rocker arm, broken valve spring, locks for valve spring/valve - there are two types - all in all everything under the valve cover). They (and I) believe that the problem is there. Be sure to go to a mechanic, who knows what he is doing - not a fancy workshop with a multi million dollar computer system. This repair needs a REAL mechanic to get it done right and for the right price.
If You have further questions, don’t hesitate to ask.