Running hot

[Jonessa]

More fun times with Molly, she seems to be running very hot, I have changed water pump, fitted a thermostat as one wasn't fitted, I have done a compression text and all good, used a sniffer kit on the radiator which didn't change colour, I confirmed kit works as I then tried it in front of exhaust and colour changed. Radiator off and flushed all clear and even temperature all over, block flushed and clear, water circulated well and heater gets extremely hot, unfortunately she doesn't have a temperature gauge fitted,any ideas please. Steve

[svenedin]

What engine do you have fitted?

When you say extremely hot does the water in the radiator boil and the cap vents steam?

You say you replaced the water pump and installed a thermostat which was absent. What thermostat did you install? Standard 82 degrees C?

Heater working well and radiator flushed and evenly hot sounds like the new water pump works well and the flushing was effective. When you flushed the block did you remove the block drain plug and check water runs out swiftly? I attached a hose to the heater tap on the head and flushed water through when I last flushed the cooling system.

What may help is to add some citric acid crystals (a cup full) to the coolant. Dissolve the crystals in hot water first then run the car up to temperature. Allow to cool and repeat several times then drain and flush again. Citric acid is used to descale kettles, washing machines etc and is safe but should not be left in the cooling system beyond the descaling process. It can be bought cheaply as crystals.

If the cooling system is absolutely fine, an over-lean fuel mixture and/or retarded ignition timing can cause an engine to run hot.

Stephen

[geoberni]

Ideas?
Yes, instead of guessing if it's hot, or not, or how hot, get an Infrared Temperature Gun, available on ebay from about £6.

Your idea of the "heater gets extremely hot" might be my idea of 'Um, that's nice and effective'....

Not just a 'medical' one for measuring a child's forehead, one for industrial use, which will also check people's temperature as well.
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temp gun.JPG (67.45 KiB) Viewed 2878 times

[svenedin]

Ideas?
Yes, instead of guessing if it's hot, or not, or how hot, get an Infrared Temperature Gun, available on ebay from about £6.

Your idea of the "heater gets extremely hot" might be my idea of 'Um, that's nice and effective'....

Not just a 'medical' one for measuring a child's forehead, one for industrial use, which will also check people's temperature as well.
.
temp gun.JPG

Very good. I have one of those. Great for balancing the central heating.....Also for detecting overheating bearings.

[exlkrs]

How hot? Before you spend money on expensive kit and throwing the parts bin at it randomly, simple check if it's actually cooling. top hose should be very hot, bottom should be significantly cooler. if not, check the rad itself.

[Bill_qaz]

Have you got a good,correct pressure radiator cap? The pressure is to raise the boiling point.
Are you loosing coolant from the overflow when you say it very hot?
Temporary put a plastic bottle under the bonnet and put the radiator overflow into it and see if its venting coolant when hot.
Is anything restricting the airflow through the radiator?
When does it get hot, when driving or when idling?

As already suggested measure the temperature, even a household thermometer held against top hose will give you an idea of how hot

[Jonessa]

Thanks for the replies, it is a 1098 engine, 82c thermostat and 4lb cap. I have changed all water hoses as all hard and cracked and flushed through all ports in block both ways when hoses off and flowed through quickly. After a run of around 30 minutes and engine turned off you can sometimes hear a gurgle in the coolant system. It does sometimes spit water out of cap and level drops right down so can only just be seen in top of fins. No oil in water or vice versa, looks like I need to get thermometer as suggested to pinpoint any hotspots. I have not checked timing yet, plugs perfect colour but definite lack of power at top end as struggling to get to 50, but runs very sweetly especially on tick over. Steve

[les]

I wonder if there’s air trapped in the system.

[svenedin]

OK. Suggest you check the ignition timing which might explain the lack of power and the running hot. Also if you are going over stuff systematically, check the valve clearances. The book figure is 12 thou but setting the gap a bit bigger gives the exhaust valve more time to cool before it shuts which is useful with modern unleaded fuels. I use 14 thou which works well and is not too noisy at the top end. Sounds like the fuel mixture is already there.

Stephen

[geoberni]

Very good. I have one of those. Great for balancing the central heating.....Also for detecting overheating bearings.

When I fitted a temp tensor to Basil, I didn't want to get a modern gauge with Deg C marked on it.
Browsing at an Autojumble, I found a classic period Smiths gauge (for the Princely sum of £4) with just C-N-H marked on it. It was also one with the adjustment holes in the back.
Using my Temp Gun I could check the engine was at normal operating temp, with the Thermostat Housing indicating mid 80's C and adjust the gauge needle to mid range.

[geoberni]

Thanks for the replies, it is a 1098 engine, 82c thermostat and 4lb cap. I have changed all water hoses as all hard and cracked and flushed through all ports in block both ways when hoses off and flowed through quickly. After a run of around 30 minutes and engine turned off you can sometimes hear a gurgle in the coolant system. It does sometimes spit water out of cap and level drops right down so can only just be seen in top of fins. No oil in water or vice versa, looks like I need to get thermometer as suggested to pinpoint any hotspots. I have not checked timing yet, plugs perfect colour but definite lack of power at top end as struggling to get to 50, but runs very sweetly especially on tick over. Steve

it does sound as though it's getting a bit overheated, but quite honestly, buried in this statement are a couple of Red Flags which weren't previously mentioned.

struggling to get to 50

I have not checked timing yet

Get that timing checked and as Stephen has said, look at the valve clearances.
I have lost track of the number of times I have read the comment from Phil....

The valve clearances for use with unleaded fuel are inlet valves 0.012" and exhaust 0.015".
It has to be remembered that the 0.012" for both inlet and exhaust was predetermined for use with leaded fuel. The valves can run especially the exhaust valve a lot hotter with unleaded fuel so reducing the valve to rocker clearance.
Oil seals especially top hat seals should not be fitted to the exhaust valve guides as the exhaust valve stem needs all the lubrication it can get.
I have found that when the valve clearances are set at 0.015" for both inlet and exhaust the engine runs better though with a little bit more noise.

viewtopic.php?p=657759#p657759

[simmitc]

Struggling to get over 50 and running hot. Is anything else hot - are the brakes binding? Is there a tight wheel bearing? Check that each wheel spins freely and smoothly. If disk brakes fitted, was the master cylinder modified correctly? After a run, check that none of the wheels/drums are excessively hot.

[svenedin]

Struggling to get over 50 and running hot. Is anything else hot - are the brakes binding? Is there a tight wheel bearing? Check that each wheel spins freely and smoothly. If disk brakes fitted, was the master cylinder modified correctly? After a run, check that none of the wheels/drums are excessively hot.

Very good points Simon!

[Bill_qaz]

Getting all the information for fault finding is like squeezing oranges. The longer you squeeze the more you get

[Jonessa]

I will be checking timing and valve clearances when I get back off holiday, all brakes free has disks on front and I have fitted a new genuine master cylinder and removed the seal before fitting, new rear wheel cylinders and shoes, no binding and no hot wheels, already checked that one as brakes were all shot from standing over 3 years before I bought her in February. See what happens with thermometer and other adjustments thanks Steve

[Bill_qaz]

Well worth fitting a temp gauge for peace of mind.
Normal water level is just over the core as it needs expansion space, if you fill it more it just vents to that level. Unlike modern vehicles with expansion tank were the water is drawn back during cooling.

[svenedin]

Well worth fitting a temp gauge for peace of mind.
Normal water level is just over the core as it needs expansion space, if you fill it more it just vents to that level. Unlike modern vehicles with expansion tank were the water is drawn back during cooling.

Exactly. If you overfill it just gets chucked out of the overflow. It find its own level which as you say, is just above the core.

Stephen

[geoberni]

Well worth fitting a temp gauge for peace of mind.
Normal water level is just over the core as it needs expansion space, if you fill it more it just vents to that level. Unlike modern vehicles with expansion tank were the water is drawn back during cooling.

Yes, the book says 1/2" below the top of the filler orifice, which seems a bit arbitrary, considering that was originally written for the SII High Top Radiator.
Personally, whatever the car (pre-expansion tank era) I've always aimed for half way between top of core and the 'filler orifice'.

There was someone on one of the farcebook groups a year or so ago complaining about their Radiator venting; it eventually transpired they were filling it to the top every time...

[svenedin]

It's an easy mistake for a new owner. It's not like a modern car with a clear max/min line on the expansion tank.

Our Minors on Tour WhatsApp chat is getting busy with chatter from owners starting their journeys to France from all directions, Norway and Spain included. They are 72 Minors this year. Already somebody has had the first overheat problem. This often seems to happen on the way to the ferry. This particular case seems to have been caused by an over-lean fuel mixture.

Incidentally, in an emergency obviously stop and let the engine cool down. Then if you can't rectify the problem, try to proceed with the heater turned on. This will dump extra heat and may be enough to get to wherever you're going. Rectify the problem as soon as possible.

Stephen

[myoldjalopy]

"Already somebody has had the first overheat problem. This often seems to happen on the way to the ferry."
If this is the case, I wonder how often these cars are used during the rest of the year? Of course, things can go wrong at any time but this seems more than coincidental. When I was a boy, a Morris Minor driving great-aunt impressed upon me how the cars need regular usage, a bit like exercise