22 replies to this topic

[Peter_NottinghamS]

After a very jerky, difficult run around the country lanes yesterday, with a loss of power and very poor throttle response, I did a quick spark test and compression test earlier today.

Each lead/cylinder showed a healthy spark and the compression test (each cylinder was tested individually although I know some advocate removing all the plugs) was as follows (with cylinder 1 being the furthest from the radiator).

1: 150
2: 145
3: 125/135
4: 150

The plug on cylinder 3 was very wet.

The coolant is a browny colour and but the is not sign of milky cream in the engine oil.

I suspect it's the cylinder head gasket.

Thoughts?

Thanks in advance.

Peter

[MiniMadRacer]

In my experience Mini (A series) head gaskets rarely fail unless a few things have come in to play...

 

1) Poorly fitting in the first place, this includes cheap gaskets, incorrectly torqued head nuts, warped head inferior bolts etc etc

2) Abused in use, ie run with inadequate cooling ending in a massive over heated engine.

 

Assuming none of the above, how long has the engine been running without any issues.

 

Though those readings are low, I would suspect other issues, like total lack of maintenance, including the ignition system, but of course I am guessing

[Ethel]

Wouldn't be my primary diagnosis. The figures seem reasonable if the other plugs were left in. I'd be looking at the ignition for starters. clean &  file the points (if applicable) swap the condenser (if you have a spare). Clean & inspect the distributor cap, rotor arm leads, coil wiring....

[MiniMadRacer]

Re Reading your post, healthy spark outside of combustion compression is not the same as a healthy spark inside compression, are you running points, or electronic ignition, how old is the rotor arm, leads, dist cap condenser, coil etc.... (just my late night experienced ramblings)

[68+86auto]

I don't believe it's the head gasket or head at fault.

 

Those values are close enough that possibly just a misfiring cylinder has washed the bore of oil so the rings can't seal well. Clean the plug and then switch it and the lead with another cylinder. If the "wet" plug symptom moves to the other cylinder then you know it's the plug or lead.

 

 

A head gasket can easily fail in a way that you won't get coolant in the oil but will get combustion gasses in the cooling system. There's a few ways to test:

- is there bubbling visible with the cap removed?

- does it lose a lot of coolant due to over pressurising the system?

- attach a cooling system pressure tester and rev the engine, if it builds pressure when you rev it then the gasket or head is bad.

- stick the probe of an exhaust analyser into the air of the radiator tank. If you see the HC go up above the ambient air then your gasket or head is bad.

 

DO NOT blame it on a head gasket until it is verified with proper test methods such as above and preferably the bottom two. Too many people are quick to blame head gaskets.

Edited by 68+86auto, 25 September 2024 - 10:41 PM.

[Peter_NottinghamS]

In my experience Mini (A series) head gaskets rarely fail unless a few things have come in to play...

 

1) Poorly fitting in the first place, this includes cheap gaskets, incorrectly torqued head nuts, warped head inferior bolts etc etc

2) Abused in use, ie run with inadequate cooling ending in a massive over heated engine.

 

Assuming none of the above, how long has the engine been running without any issues.

 

Though those readings are low, I would suspect other issues, like total lack of maintenance, including the ignition system, but of course I am guessing

 

You say the readings are low.  What would you expect?

There's further info in my reply below.

Thanks for sharing your knowledge and experience.

 

 Peter
 

[Peter_NottinghamS]

A little background on the car.  He's this one mentioned in my Introduction thread:

https://www.theminif...ears/?p=3773267

 

Since getting him he's run very poorly and has been dyno-tested at Southam Minis, so I was expecting him to run a lot, lot better.

Apparently he's pushing out 88bhp, and once on the cam, he feels like 88bhp.  However, he stinks of petrol (there's a leak somewhere) and the exhaust tailpipe is as black as soot.

Since his rebuild, he's done less than 600-miles since the engine rebuild, but I sense the build was rushed.

 

Here's a list of jobs that will be done over winter:

1. Sort out rough running/head gasket issue (if it is the head gasket).
2. Fit a heater control cable. 
3. Get the horn to work. The one it came with stopped working and I cannot find the second wire to fit to the new one.
4. Brakes: they are awful and pull violently to the left under emergency braking.  No servo; do I need one.
5. Get a new spare JBW spare wheel.
6. Source all the oil leaks.
7. Improve the cooling system; he has a Fletcher radiator but I'm surprised there is no oil cooler.  He hates traffic and the temperature quickly rises.
8. Sort the rear wheel camber; either shims or adjustable brackets.
9. Fit a rev counter.
10. Add additional exhaust brackets; the stainless steel exhaust is wobbling and banging around.
11. A billion other small fix, cosmetic jobs.

I've raced and rallied Minis in the past and done just about every job to do, from setting plug gaps to rebuilding gearboxes.  But it was all a long-time ago.

 

My wife loves the car and we are recording "Marvin's Adventures" as we go.

 

You'll be seeing a lot of me with questions on all of the above and more. 

 

:) Peter 

[Peter_NottinghamS]

Wouldn't be my primary diagnosis. The figures seem reasonable if the other plugs were left in. I'd be looking at the ignition for starters. clean &  file the points (if applicable) swap the condenser (if you have a spare). Clean & inspect the distributor cap, rotor arm leads, coil wiring....

 

This makes sense.  I suspect the HIF44 carb needs a good rebuild but I'm also looking at the basics: fuel, air, fire (spark).

 

Thank you.

 

Peter 

Edited by Peter_NottinghamS, 26 September 2024 - 11:39 AM.

[Peter_NottinghamS]

Re Reading your post, healthy spark outside of combustion compression is not the same as a healthy spark inside compression, are you running points, or electronic ignition, how old is the rotor arm, leads, dist cap condenser, coil etc.... (just my late night experienced ramblings)

 

It's electronic ignition, which for me is dark art and voodoo.

 

Peter

[Peter_NottinghamS]

I don't believe it's the head gasket or head at fault.

 

Those values are close enough that possibly just a misfiring cylinder has washed the bore of oil so the rings can't seal well. Clean the plug and then switch it and the lead with another cylinder. If the "wet" plug symptom moves to the other cylinder then you know it's the plug or lead.

 

 

A head gasket can easily fail in a way that you won't get coolant in the oil but will get combustion gasses in the cooling system. There's a few ways to test:

- is there bubbling visible with the cap removed?

- does it lose a lot of coolant due to over pressurising the system?

- attach a cooling system pressure tester and rev the engine, if it builds pressure when you rev it then the gasket or head is bad.

- stick the probe of an exhaust analyser into the air of the radiator tank. If you see the HC go up above the ambient air then your gasket or head is bad.

 

DO NOT blame it on a head gasket until it is verified with proper test methods such as above and preferably the bottom two. Too many people are quick to blame head gaskets.

 

I've learnt so much diagnostic tips from your reply.  Thank you.

To answer your points:

 

• Visible bubbling?  I don't know but I will check
• It doesn't seem to loose coolant
• testing the pressure of the coolant system is a great suggestion.  How I do it is another matter.  I do have a pressure test kit but how I plug it into the coolant system is something I'll have to explore.  The results will be very revealing. Thanks.
• I don't have an exhaust gas analyser.  Where can I get one?  There is an MOT centre 500-metres away, so I could ask them to do this.

 

I'm not blaming the gasket, I'm trying to rule it out.

 

I'm very suspect of the carb and I may consider twin carbs for next year. 

 

At the weekend, I'll be doing the basics:

 

1. Clean the engine bay; the rocker cover gasket is leaking so I'll gunk the engine and fit a new one.
2. I'll do another compression test with all the plugs out.
3. Go though the ignition system, checking all connections.
4. Repeat the spark test.
5. Inspect the carb and check the dash pot oil levels
6. Try and perform some of the tests you recommend above.
7. Report back.

Thanks @68+86auto and everyone for you time, advice and suggestions.

 

I can see this being a knuckle bashing, frustrating but fun experience.

 

Peter 

[DeadSquare]

If you have a wet plug, you may have a duff one, but it wouldn't break the bank to treat your Mini to a new set of plugs.  While you are shopping, I'd buy a new set of plug leads and caps.  The don't last for ever.

 

To test for a cylinder to water-way leak, remove the radiator cap and fill to capacity.

 

Start the  engine and if you see a constant succession of bubbles when the engine is warm, then you could suspect the head gasket

[MiniMadRacer]

 

In my experience Mini (A series) head gaskets rarely fail unless a few things have come in to play...

 

1) Poorly fitting in the first place, this includes cheap gaskets, incorrectly torqued head nuts, warped head inferior bolts etc etc

2) Abused in use, ie run with inadequate cooling ending in a massive over heated engine.

 

Assuming none of the above, how long has the engine been running without any issues.

 

Though those readings are low, I would suspect other issues, like total lack of maintenance, including the ignition system, but of course I am guessing

 

You say the readings are low.  What would you expect?

There's further info in my reply below.

Thanks for sharing your knowledge and experience.

 

 Peter
 

 

I like to see around 160 PSI, but this come with a good few caveats, not necessarily a complete list

 

1) Mileage

2) Throttle held wide open

3) Fully charged battery

4) All plugs removed

5) Engine hot and oil up to temperature

6) CAM dependent (Sportier CAMS will give lower PSI reading at cranking speeds)

7) Healthy starter motor

[Peter_NottinghamS]

 

 

In my experience Mini (A series) head gaskets rarely fail unless a few things have come in to play...

 

1) Poorly fitting in the first place, this includes cheap gaskets, incorrectly torqued head nuts, warped head inferior bolts etc etc

2) Abused in use, ie run with inadequate cooling ending in a massive over heated engine.

 

Assuming none of the above, how long has the engine been running without any issues.

 

Though those readings are low, I would suspect other issues, like total lack of maintenance, including the ignition system, but of course I am guessing

 

You say the readings are low.  What would you expect?

There's further info in my reply below.

Thanks for sharing your knowledge and experience.

 

 Peter
 

 

I like to see around 160 PSI, but this come with a good few caveats, not necessarily a complete list

 

1) Mileage

2) Throttle held wide open

3) Fully charged battery

4) All plugs removed

5) Engine hot and oil up to temperature

6) CAM dependent (Sportier CAMS will give lower PSI reading at cranking speeds)

7) Healthy starter motor

 

 

He's done very few mils since the (re)build, we only turned it over until we got a reading on each cylinder, the battery is good/new, each cylinder was tested, one at a time, the engine was cool, he has a high lift cam and a Janspeed stage 3 head, hence the likely lower than expected readings?

 

Peter 

Edited by Peter_NottinghamS, 26 September 2024 - 12:40 PM.

[68+86auto]

 

I don't believe it's the head gasket or head at fault.

 

Those values are close enough that possibly just a misfiring cylinder has washed the bore of oil so the rings can't seal well. Clean the plug and then switch it and the lead with another cylinder. If the "wet" plug symptom moves to the other cylinder then you know it's the plug or lead.

 

 

A head gasket can easily fail in a way that you won't get coolant in the oil but will get combustion gasses in the cooling system. There's a few ways to test:

- is there bubbling visible with the cap removed?

- does it lose a lot of coolant due to over pressurising the system?

- attach a cooling system pressure tester and rev the engine, if it builds pressure when you rev it then the gasket or head is bad.

- stick the probe of an exhaust analyser into the air of the radiator tank. If you see the HC go up above the ambient air then your gasket or head is bad.

 

DO NOT blame it on a head gasket until it is verified with proper test methods such as above and preferably the bottom two. Too many people are quick to blame head gaskets.

 

I've learnt so much diagnostic tips from your reply.  Thank you.

To answer your points:

 

• Visible bubbling?  I don't know but I will check
• It doesn't seem to loose coolant
• testing the pressure of the coolant system is a great suggestion.  How I do it is another matter.  I do have a pressure test kit but how I plug it into the coolant system is something I'll have to explore.  The results will be very revealing. Thanks.
• I don't have an exhaust gas analyser.  Where can I get one?  There is an MOT centre 500-metres away, so I could ask them to do this.

 

I'm not blaming the gasket, I'm trying to rule it out.

 

I'm very suspect of the carb and I may consider twin carbs for next year. 

 

At the weekend, I'll be doing the basics:

 

1. Clean the engine bay; the rocker cover gasket is leaking so I'll gunk the engine and fit a new one.
2. I'll do another compression test with all the plugs out.
3. Go though the ignition system, checking all connections.
4. Repeat the spark test.
5. Inspect the carb and check the dash pot oil levels
6. Try and perform some of the tests you recommend above.
7. Report back.

Thanks @68+86auto and everyone for you time, advice and suggestions.

 

I can see this being a knuckle bashing, frustrating but fun experience.

 

Peter 

 

 

What is the "pressure test kit" that you have?

 

An exhaust gas analyser is unfortunately very expensive unless you find an old one. I knew you wouldn't have one but it's a suggestion in case you know someone with one like the MOT place. It's also ideal for tuning of course.

 

 

 

Your list sounds good except I'd skip the spark test. Looking at the spark outside of the engine is of little use. Since you mention cooling issues, I bet your ignition or fuel system is incorrectly setup or adjusted.

 

You need to check the ignition system and verify that it is working 100% before proceeding. That means you need to check that the advance is working correctly throughout the RPM range and that the vacuum advance works without leaks.

 

Only once you have verified that the ignition system is working do you move to the fuel system. Check that all the breathers are correctly connected and that the cap isn't blocked up.

Edited by 68+86auto, 26 September 2024 - 12:45 PM.

[Ethel]

My pressure test kit is to squeeze the top hose. If you can feel much difference before it's likely to have got anywhere near boiling, it could be the gasket.

 

A failed choke O ring is a farly classic fault for a HIF carb to get if it's stood idle for a while. If you take the dashpot off you can see the choke jet, it's just a little hole, to the engine side of the main jet, at the bottom of the "ramp". Blowing down the float chamber vent pipe should eject fuel from both jets - but not the choke if it's off. Stick a finger over the main jet, to make it clearer where any fuel is coming from.