Overheating

[martyn yates]

On a recent trip to Wales I noticed the temperature rising, along with the smell of couldn't. On inspection engine bay covered in coolant . No damaged hoses and no leaks from the radiator, lost about 2 liters of water. Topped up and continued, no further issues. On the return journey same again, but pulled over and noticed water escaping from under the radiator cap. Have purchased a new cap from esm. New cap fitted and rad focussed out and closer inspection of the hoses, also did a compression test to rule out head gasket, all cylinders ok.
Just running around town no problem, it only occours at higher speeds for example on the motorway.
Has anyone got any suggestions, should say 1957 Minor saloon, with standard running gear 948 engine.

[myoldjalopy]

Can we assume that this is a recent problem and that you have not made any adjustments to the fuel mixture or the timing recently?
You say you flushed out the rad, but did you flush the engine block as well?
It could be a faulty thermostat, if everything else is OK.
I am also wondering if the problem has been solved since you fitted the new cap and flushed the rad - is it still an issue on long, high speed runs?

[ManyMinors]

If you drain the coolant, do the tubes in the radiator look clear? It could simply be that the radiator has become blocked.
Have you tried another decent run since replacing the radiator car?
I'm assuming you've checked the fanbelt and that the water pump is doing its job?
Does the car overheat standing in traffic ticking over?

[martyn yates]

Yes I have flushed the engine as well, and made sure all the hoses are clear. Since fitting the new cap the problem persists when running fast on longer runs. The thermostat I believe is ok , with the cap off and the engine cold it takes 10 mins for it to open and the hot water to enter the top of the rad. Fan belt is adjusted correctly, how will I know the water pump is ok?
I have not made any adjustments to the fuel air mixture, or timing.
Never had any cooling issues before this.
Any suggestions, thank you for your replies.

[martyn yates]

When just running around 40 45 mph no issues and never overheats when sitting in traffic. It shows this problem when either climbing or running fast, once bact to 40ish the temperature goes back to normal.

[Boomlander]

The water pump may not be up to the job.
Remove, inspect and replace if necessary.
It is easy to do and not expensive.
Good luck!

[martyn yates]

When just running around 40 45 mph no issues and never overheats when sitting in traffic. It shows this problem when either climbing or running fast, once bact to 40ish the temperature goes back to normal.

[myoldjalopy]

Climbing hills and going faster will create more heat, as the engine is working harder. So, if all else is in order, the cooling system is not working efficiently. If rad and engine waterways are clear and hoses good, fan belt not slipping etc. then it suggests a compromised water pump or maybe the thermostat isn't opening fully - just enough for lower speeds, but not enough when more heat is being generated?

[martyn yates]

Thank you for your help, I will try the thermostat, just need to get a new gasket. Failing that the water pump does seam the next logical step.
Oh the joys of classic motoring, although I do love a tinker session.

[Bill_qaz]

Check also the air flow through the radiator is not restricted. Buy or borrow an infrared temperature gun and check difference across the radiator top to bottom and left to right, you could have some blocked tubes so not all the rad surface is being used.

They are cheap and good enough for DIY use as example
https://www.ebay.co.uk/itm/354434584976 ... media=COPY

[oliver90owner]

Check also the air flow through the radiator is not restricted. Buy or borrow an infrared temperature gun and check difference across the radiator top to bottom and left to right, you could have some blocked tubes so not all the rad surface is being used.

They are cheap and good enough for DIY use as example
https://www.ebay.co.uk/itm/354434584976 ... media=COPY

A blocked radiator is the first thing to check - but one doesn’t need an IR thermometer.

Remove fan and await the engine thermostat to open. If the rad is clear all the tubes should be hot. If they are only hot in the centre, back-flush the radiator as the first attempt.

The water pump is unlikely to be the problem if the water flow across the radiator top tank is good, and increases markedly if the engine is revved.

Also, check the bottom hose temperature under normal operation. That should tell you something - if really hot coolant is returning to the engine.

I expect you have either a partially opening thermostat or a blocked radiator.

[Bill_qaz]

Check also the air flow through the radiator is not restricted. Buy or borrow an infrared temperature gun and check difference across the radiator top to bottom and left to right, you could have some blocked tubes so not all the rad surface is being used.

They are cheap and good enough for DIY use as example
https://www.ebay.co.uk/itm/354434584976 ... media=COPY

A blocked radiator is the first thing to check - but one doesn’t need an IR thermometer.

.

You don't need IR temperature reader but far more accurate than feeling with your hand and way safer on a running engine. Also useful for checking cylinder temps for misfires and brake temps, hubs etc.
But we all have our own methods, I've used them in the vehicle industry for years and they have now become very cheap.

[geoberni]

You don't need IR temperature reader but far more accurate than feeling with your hand and way safer on a running engine. Also useful for checking cylinder temps for misfires and brake temps, hubs etc.
But we all have our own methods, I've used them in the vehicle industry for years and they have now become very cheap.

I agree, I've used one for all sorts of things, balancing radiators at home, and checking the temp of the Thermostat housing when it opens.
That's how I set up my Classic, adjustable, Smiths Temp Gauge to the new Sender. Mid range on the Gauge at around 84 deg.
Certainly a lot safer than feeling hot surfaces, or being tempted to try that while the engine is running....

[oliver90owner]

You don't need IR temperature reader but far more accurate than feeling with your hand and way safer on a running engine. Also useful for checking cylinder temps for misfires and brake temps, hubs etc.
But we all have our own methods, I've used them in the vehicle industry for years and they have now become very cheap.

Quite agree, but I would simply switch off the engine immediately prior to checking - just plain common sense. Do you really need that much “accuracy” for a simple, basic check?

A cylinder misfire is very evident if the plug lead to that cylinder is grounded - no appreciable change in engine speed (grounding other plug leads will to the engine running on only two cylinders).

I compare brake temperatures by feel - starting at a safe distance from a potentially very hot spot - saves me burning myself.

If I were diagnosing/mending vehicles as a business (so every-day usage) I would invest in more technical instruments - but I’m not, so I use my senses to aid diagnosis. I really do believe in the KISS Principle for most checks. These cars are at least 50 years old and mostly seventy years old technology - only the most specialised workshops had your sort of gear available, but it was simply just not necessary for maintaining these engines in good fettle.

I do have an IR thermometer, as well as other types - and most don’t need a battery in order to provide a read-out. These engines are not exactly at rocket science level, after all.

[Bill_qaz]

as I stated in my post we all have our own methods, so rock on with whatever you prefer.
They didn't have mobile phones either but we all use them.
I work on a wide range of classics and will use the tools that make the job easier but what would I know after 55 years of working on vehicles.

[oliver90owner]

Don’t worry about it, I will always offer the simple (and very the cheaper) alternatives to the modern technology wherever necessary. With regards to your mobile phone comment, I wonder how you possibly managed to survive before they were invented.

I do have a mobile phone but have rarely used it, over the last 15 years. I am certainly not addicted to it like some obviously are. Most certainly they are not used by everyone - and not all the time.

I recently “up-graded” to a ‘smart’ phone for possibly easier charging/operation of my electric car - only to find that it is pretty well useless for that. But it doesn’t stop me charging/driving my car. I just use my brain - instead of relying on the mobile phone.

[Bill_qaz]

Don’t worry about it, I will always offer the simple (and very the cheaper) alternatives to the modern technology wherever necessary. With regards to your mobile phone comment, I wonder how you possibly managed to survive before they were invented.

I do have a mobile phone but have rarely used it, over the last 15 years. I am certainly not addicted to it like some obviously are. Most certainly they are not used by everyone - and not all the time.

I recently “up-graded” to a ‘smart’ phone for possibly easier charging/operation of my electric car - only to find that it is pretty well useless for that. But it doesn’t stop me charging/driving my car. I just use my brain - instead of relying on the mobile phone.

I don't understand the relavance of anything in this reply. what is your point? Why would you think I'm worried about your post.