What's the "normal" running temperature range for coolant ?

[iain1967s]

Quick update:

Changing to an 82C high flow thermostat made little difference on a hot run. It didn't get quite as hot, but it was still up in the H.

I saw the coolant flowing in the rad when the thermostat opened, and measured it at 81.8C on a digital thermometer. So the stat is working.

Then it just got hotter and hotter, maxing out around 98C before I shut it off
(engine starts to get smokey at that temperature, as the oil is thinning and no airflow across the oil cooler when idling)

On to #3...

I drained out the waterless coolant, flushed for 15 minutes with a hose, and left it on fast idle with the rad cap off again. This time the temperature gauge got only half way between N and H.

Haven't taken it out for a run yet, its raining today but tomorrow is forecast hotter so we'll see. Am using a 0.9bar rad cap (13lb) now that it'll be a pressurized system again.

Also I didn't add the water wetter yet - just plain tap water. If it behaves itself on plain water, I'll add the wetter when I switch from water to 50:50 antifreeze, it gets cold here in New England winters...

[Spider]

I'll add the wetter when I switch from water to 50:50 antifreeze, it gets cold here in New England winters...

Ticking off the list

If you do need as much as 50/50 for the winter, can I suggest you go back to around 25/75 for summer.

Glycol, which is what the Evans stuff is, is a poor thermal transmitter, it's very slow to heat up and slow to cool down.

[iain1967s]

Well, I just took it out for a quick run and a bit of a "stress test".

Driving around town the needle stayed half way between the N and the H, which based on my previous experiments is around where the thermostat opens af 82°C. That's an improvement on the previous behavior, with waterless it would have been in the H and over 90°C under similar conditions.

It's a warm but not hot summers day (85°F/29°C). Decided to stress things by going on the highway up a hill, about a mile long and 400 ft rise in elevation, at around 60 MPH in fourth gear.

On waterless the needle would have be buried in the red per the above photo, close to 100°C. On plain water the needle also went into the red, but it didn't boil over.

I'm sure it would have come back down again fairly quickly on the other side of the hill, but I didn't want to risk it on this first run so I pulled over into a parking lot for things to settle down.

(Also rather stupidly tried to open the radiator cap with a cloth over it to measure the water temperature with a digital thermometer - as I had been doing with waterless. I can report that it's definitely a pressurized system now, as evidenced by the two pints of boiling water that ejected across the engine, and the blister I now have on my right hand I won't be doing that again!)

Anyway I'm going to drive it like this for a while and see how it behaves generally in traffic etc. and then I might put the water wetter in as well for further comparison.

Also, if the results are still marginal, I won't put any antifreeze in until I lay the car up for winter storage.

[winabbey]

Out of interest, the BMC Australia engineering drawing for the locally made Smiths temperature gauge as fitted to Australian built cars shows a design temperature of 52C at the Cold mark and 120C at the Hot mark (subset of the drawing below).

AYA9168 Temperature Indicator YDO5 subset.jpg

[Spider]

Glad that you are making some further progress with it.

I won't put any antifreeze in until I lay the car up for winter storage.

That's fair enough, however, I would suggest adding something to the system to prevent rust & corrosion.

[Exminiman]

With a new engine (specifically a new head gasket) you should run with straight water for around 200 - 300 miles, then go over to a water based coolant.

Intresting, not heard this before, is this so HG seals or sets before adding antifreeze?

[Spider]

With a new engine (specifically a new head gasket) you should run with straight water for around 200 - 300 miles, then go over to a water based coolant.

Intresting, not heard this before, is this so HG seals or sets before adding antifreeze?

Yes.

Most Coolants 'thin' the water and remove it's surface tension, so they can leak like a bastard.

ACL (gasket & bearing manufacturer) for one recommend this.

[Exminiman]

With a new engine (specifically a new head gasket) you should run with straight water for around 200 - 300 miles, then go over to a water based coolant.

Intresting, not heard this before, is this so HG seals or sets before adding antifreeze?

Yes.

Most Coolants 'thin' the water and remove it's surface tension, so they can leak like a bastard.

ACL (gasket & bearing manufacturer) for one recommend this.

Live and learn....cheers for that “top tip”.

[iain1967s]

I would suggest adding something to the system to prevent rust & corrosion.

thanks. Yes, I'll be flushing again and the water wetter will be going in, that should be good enough corrosion protection for summer I think. Just want to get a good idea first of its behavior on plain water as a baseline.

[Spider]

I would suggest adding something to the system to prevent rust & corrosion.

thanks. Yes, I'll be flushing again and the water wetter will be going in, that should be good enough corrosion protection for summer I think. Just want to get a good idea first of its behavior on plain water as a baseline.

Does Wetter Water have an anti-corrosive agent? I don't know as I've not used it, but heard of it,

Live and learn....cheers for that “top tip”.

(Hopefully this will work) Here's the sheet from ACL:-

[iain1967s]

Does Wetter Water have an anti-corrosive agent?

In the data sheets it says "Rust and corrosion protection allows for use of straight water in racing or reduced antifreeze levels in warm climates. Satisfies ASTM D2570 and ASTM D1384 corrosion tests. The anti-scaling ingredients in Red Line WaterWetter allow its use with ordinary tap water. However, using with distilled or deionized water will accomplish some scale removal in the cylinder head area."

So that sounds good enough for the summer...

[iain1967s]

Well, Summer is pretty much over so I guess it’s time to get back to this.

Distributor Doctor is building me a Lucas 23D4 with the proper curve for #4 - in the meantime, I skipped on to step 5.

I’ve just drained the summer water+wetter out, it was still quite clear although I only ran it for a couple hundred miles this summer, and replaced it with a mix of water and CLR per Spider’s suggestion.

I will say that getting to the drain plug at the rear of the block on an S is a nightmare... had to remove the engine stabilizer bar and clutch slave to be able to get a spanner to it, and still the carb heat shield and the remote brake servo make access tricky.

Have sourced a brass drain tap from Nick Rogers instead of refitting that drain plug, so hopefully easier to drain and refill in future. Of course, I had to loosen the manifold to fit that... what a faff.

Ran the engine up to temperature with the CLR and then put it back in the garage to sit and do it’s thing... will drain it next weekend and see what colour it comes out.

Next steps in order, one at a time and check for overheat on a fast run at each:
1. Replace temp sender and regulator / calibrate against digital thermometer
2. Change to high flow rate thermostat
3. Convert back to plain water with wetter
4. Change distributor (wrong advance curve?)
5. Soak the block / head waterways in CLR
6. Change to supercool radiator
7. Change water pump to non bypass
8. Finally, pull the engine apart and check cam timing.

[mk1]

"Cooper S standard cooling systems are marginal at best"

My car has a far from standard 1293 cc engine. It has never overheated either here in Australia or in Indonesia even in traffic with temperatures in the 40s (degrees C). The cooling system is standard 1967 stuff except no bypass hose. None of my Mini's ever overheated in hot weather. So I guess in my experience anyway, the cooling system is entirely adequate for hot climates. I use standard off the shelf coolant (mainly for the corrosion inhibitors).

I totally agree with these comments. I run a bog standard cooling system on my hillclimbing Hornet, in 3 years of track & hill events & 3 Blytons it has NEVER gone above 90° (one strike temperature sticker on the rad).

If all components are working as they should then a 1275 Cooper S even in mild tune should be between 75° & 90° in pretty much all conditions.

I have no experience of waterless coolants, apart from watching cars skidding of the track on it after it was dumped by someone else. That's why its been banned by the MSA now

[abri]

Same here. I run two S's, one slightly tuned 1275 and an otherwise standard 1293 here in Cape Town. Both have tropical fans. I struggle to get the 1293 up to N. It needs some attention in fact. The 1275 will only go halfway between N and H when I put my foot down up a hill in 35 degree weather.

[iain1967s]

Thanks. Something is clearly wrong, I just haven't found yet what it could be...

Does anyone know what the temperature drop across the radiator should be?

e.g. at idle on a warmed engine, what should the radiator inlet vs outlet hose temperatures be
(I have with an IR gun)

My rebuild was deliberately kept as close to standard 1275 S as I could get.

Radiator: ARP1105 3-core 'Cooper S'
Water pump: 12G2324 Cast Iron deep impeller, with bypass
Engine: Thin flange 'S' block at 1293 (+20)
AEG163 head, AEG510 spec cam
AF460 head gasket / Copper Coat sealant
82C high-flow thermostat, 13LB rad cap
6 blade tropical fan and 'S' large pulley

I originally thought waterless was a contributing factor, but plain water with wetter isn't really very much better and the coolant in the radiator is always close to boil-over.

Running with the heater turned on helps a little, so I wondered if it could simply be a bad radiator - it was new from MiniSport last year.

If the new distributor and the CLR don't resolve the issue, then per my checklist a MiniSpares ARA4442 supercool radiator is next on the hit list. But given how much of a pain it is to change the water pump and radiator in-situ on a Mk1, I'll probably pull the head and do 6/7/8 all at the same time over the winter.

Is there a good manual process to follow for de-scaling/de-rusting the waterways in the block when the head is off?

[smithyrc30]

Does anyone know what the temperature drop across the radiator should be?
e.g. at idle on a warmed engine, what should the radiator inlet vs outlet hose temperatures be
(I have with an IR gun)

My rebuild was deliberately kept as close to standard 1275 S as I could get.
6 blade tropical fan and 'S' large pulley

Is there a good manual process to follow for de-scaling/de-rusting the waterways in the block when the head is off?

Temperature drop across the radiator is far too dependant on the internal and external conditions to give any sort of meaningful answer. The inputs to the equation are coolant mass flow, air mass flow, air onto radiator temperature, air off radiator temperature, coolant specific heat capacity, coolant inlet temperature and coolant outlet temperature.
As the heat transfer is majorly dependant on the air temperature onto the radiator, defining what it should be on any given day is a little tricky.
If you want a thumb in the air approximation, about 6 to 10 degrees celsius would be what I would expect on an engine at idle, running normally.

One thing you could do is remove the large pump pulley and fit the smaller pressed one. This will increase the water flow and the fan speed for any given engine speed. As far as I am aware the large pulley was there to prevent water side cavitation at high engine speeds (mainly encountered in competition usage) so if you are not usually spending a long time at 6000+ RPM then it most likely would not be an issue for you. Changing to the 16 blade plastic fan would also increase air flow.

The only way I have ever seen an iron block/head descaled completel is with an acid dip. Everything else leaves residue and in some cases (for example if someone has used Bars Leak) passages still blocked.

[iain1967s]

Ran the engine up to temperature with the CLR and then put it back in the garage to sit and do it’s thing... will drain it next weekend and see what colour it comes out.

Well the CLR went in light green a week ago and came out mid brown tonight. So it must have done something

I flushed through well with a garden hose then drained again and refilled with a mix of 50:50 antifreeze and a pint of premixed water wetter.

Also fitted another new 82C thermostat as there seemed to be quite a lot of green salt crystals attached it, presumably from the CLR. Am hoping those will dissolve again over time.

Heading to an end-of-summer classic car meet tomorrow, so we’ll see how it behaves on the highway...

[iain1967s]

The game continues...

Unfortunately the results from a week soaking in CLR were inconclusive. Driving at 55-60 MPH the temperature gauge goes just onto the line at the start of red and stays there. This is on 2/3 of 50:50 antifreeze with the other 1/3 topped up with a mix of water-wetter and distilled water.

Ambient air temperature was 21°C / 70°F today so not too stressful, and adjusting for the antifreeze I think this shows about the same as previous results. Running with the heater on is sufficient to stop it boiling over. Heater off and it drifts into the red and starts spitting coolant out the overflow within a few minutes.

Maybe time for a lesson in heat machine / engine thermodynamics from Peter but this behaviour suggests to me that there’s no problem getting the heat out of the block/head and into the coolant, and the real problem is getting the heat out of the coolant and into the air (or there is simply too much heat being generated in the first place, due to a fault).

Smithyrc30 made an interesting post (thanks!) that maybe the pump isn’t circulating fast enough. I can see it flowing in the radiator when the thermostat opens, it looks about the same as I remember from 30 years ago on my last Mini, and the heater seems to work fine. I have no way of actually measuring the flow rate, but I do also have the small pressed-steel pulley, so I just ordered the shorter fan belt and will give that a try as suggested.

But first up... another week soaking in chemicals - this time some stuff bought off Amazon to try cleaning the engine and radiator one last time before I start replacing things. I also got a cheap gun/rifle barrel cleaning kit, figured I could use it to try and manually de-clag the vertical waterways in the block when I (inevitably) take the head off.

[iain1967s]

One thing you could do is remove the large pump pulley and fit the smaller pressed one. This will increase the water flow and the fan speed for any given engine speed. Changing to the 16 blade plastic fan would also increase air flow.

Looks like the chemical soak will have to wait until spring, as we’re getting frosts now and the instructions say it has to be used with plain water. Last thing I want is that stuff freezing and cracking the block...

Next up, I am taking smithyrc30’s suggestion and fitting the smaller pressed steel pulley, with a new Minispares evolution alloy pump and no bypass for #7 on the list, replacing the cast iron bypass pump and large pulley.

However I will be refitting the 6-blade ‘tropical’ metal fan, as the plastic types are “visually wrong” for a ‘67 S; the rivet-counters are sure to spot it at shows - but a black painted alloy pump is less obvious

Am also fitting the Minispares super cool 2-core radiator for #6 on the list while everything is accessible. Just as well, as there was a pinhole leak at the top of one core tube on the rear. I can easily solder it up, so will keep as a spare - along with the cast iron pump which could do with new seals as it was also weeping.

[iain1967s]

Final pieces of the jigsaw arrived, at least for now...

#5 refurbished 40819 from the Distributor Doctor
#6 MiniSpares supercool radiator
#8 measured the cam timing, 109° on the inlet (avg of 5thou before/after max lift)

But it all has to wait until Spring to be put to the test...

The graph shows ‘all in’ by 3500rpm, with 14 degrees centrifugal distributor advance. I think that means 28 degrees crankshaft advance, so static ignition timing should be between 4 and 6 degrees before top dead center, to hit the magic 32-34° total?

I also used (wrecked!) the gun barrel cleaning set to scrub crud off the inside of the vertical cylinder block waterways, in case flow between the head and block was the issue. Nothing was obviously blocked there, came up pretty clean and smooth.