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

[iain1967s]

Took my 1967 S out for the first real run today since rebuilding the original engine.

Expected it to run a little hot due to things being tight etc. but the temperature gauge went right across to maximum within a few minutes of driving.

Lots of things have changed since it's last run [engine, fan, water pump, voltage regulator, wiring loom, radiator, temperature sender] so I don't really have any confidence that the temperature gauge is correct.

It was a hot day at 31°C - but I'm running a tropical 6-blade fan, 75°C thermostat and 3-row 'S' rad, so it should be more than able to cope.

I decided, perhaps foolishly, that it must be a gauge/sender/regulator issue and drove it home with no ill effects. But after letting the heat soak for a few minutes on the driveway, I measured the coolant in the radiator header tank with a cooking thermometer. Exactly 102°C. That seems high ?

This is a non-pressurized system, using Evans waterless coolant, hence why it was safe to open the radiator cap to measure.

I know the Cooper S standard cooling systems are marginal at best, and I suspect the Evans has raised the temperature ceiling, but as I've never run a standard S engine before I have nothing to compare against as to whether 102°C really is 'too hot'.

My question: what is the "normal" temperature range supposed to be? i.e. What approximate coolant temperatures is the Smiths gauge supposed to be 'calibrated' at, for C, N and H ?

Need to understand if it's really running too hot, or if this is just an instrumentation issue, before I cook something badly in the engine...

Thanks.

[Spider]

A few things here.

Firstly, the 102 deg you've measured is perhaps a little meaningless as the temp really needs to be measured with the engine running. If it's measured after a run and shut down, it will go up pretty high for a while and the pump is no longer working and neither is the fan.

Do your own research (even a search on this forum will bring up some results) on the Evans coolant, in these engines, it's bad news. It will make your engine run hotter and the cooling system overall has a reduced capacity to transfer heat out of the engine and it to the air with it. 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.

'N' on a Temp Gauge for a Cooper S (with all the right parts) should be 82 degrees, however, it could well vary a little either side of that. I know elect gauges come in for serious criticism however, IMO, there's nothing in the world wrong with them, just get to know how your Temp Gauge reads with your engine, ie, what's normal. Further to this regards, I would strongly suggest swapping out the 75 thermostat for an 82 degree type. A few reasons I suggest this, but one that's often over looked is that it's better to have temperature stability in the engine that something that swings from cool to warm, which is what it will do with a 75 'stat.

Lastly, given how quick your engine heated up, I suspect the maybe another issue, possibly with ignition timing, however, before worrying too much about this, sort these other issues, in particular getting rid of that coolant.

[mario abreu]

Agree with Spider 100%....
My experience tells me exactly the same.

Or you may simply have as air pocket... Or the sender wire may be grounding...

Check the scale on early gauges.

[Peter Laidler]

I only ever disagree with Chris the Spider after a great deal of trepidation and thought. Just going out but will come back later with some simple thermal physics. As opposed to the thermal physics usually associated with a million pound 500 bed hospital accommodation block..........

[Nick W]

I have changed my electric temp gauge for a capillary type with temp markers , as my electric gauge was also over the hot mark,
Now I can see the temp and it's not going above 90 on tick over, not had it out on road yet though.

[CooperTune]

My driver is powered by a 1967 Cooper S bored to 1360. It currently has a mega torque camshaft from Reed cams. I pull a lot of gear wide ratio metro gear set with 2.76 cwp and two OD drops. I have owned and used this cyl block since the early 70s. I have run it as std. .020, .040, .060 and now 73 mm. It has always run hotter than the 160/180 degrees Vizard talks about. For most of it's life it was power for a serious US Solo 2 SCCA car. First A S/P south east, third north east and top five several times at Nationals. It now enjoys retirement pulling my 85 1000 E. I run 50/50 with a little water wetter, tropical fan, 3/4 inch blanking plate in place of thermostat. Four core rad, large pulley, no oil cooler. Intake is Metro with HIF 44 and cast LCB from MPI. I run a mechanical temp gauge. It was 90 degrees here yesterday and temp gauge stayed on 210 degrees all day long. No matter weather at idle or running 75 mph down the road. At 96 mph ( my highest recorded speed on GPS ) it will creep up to 225. I do run a MGB brass recovery tank and a 15 lb cap. It has been a year or more since I have removed the cap to see if anything is in there.

What gets me thinking is the low oil temp in this unit. Oil temp remains in the 160/170 degree range. I picked up a Metro oil to water cooler / heat exchanger. Plan was to transfer some water heat to the oil. Try to balance them out. Seems there are two different length Purolator spin on filter adapters. I have the long one and will have to find a short one and notch the sub frame to make this work.

BTW I have no problem getting heat in the winter, this girl heats right up no matter outside temp. That's all I know. Steve (CTR)

[iain1967s]

Thanks everyone. I did a lot of background reading regarding waterless before I decided to use it. Mainly interested in the long term anti-corrosive properties as my car does limited annual mileage. I know it’s a divisive topic... strong opinions on both sides of the discussion.

Consensus from this and other forums suggests 80°C to 90°C is the “normal” running temperature on the mini temperature gauge, and “hot” full-scale on the gauge is around 110°C.

Before I panic and take any drastic steps like switching back to water based cooling, I’m going to take a more accurate digital reading of the coolant with the engine running, and an IR reading on the head itself. Seems that I should be aiming for 90° and anything less than 100° or so is unlikely to be causing any damage.

Regarding ignition and fueling, yes those are set only very approximately at the moment. Mixture is deliberately set slightly weak for running in, and ignition timing set 5° static for starting then I did the “find the fastest point then back off 250RPM” method.

I am using a new Minispares 12G2140 non-vacuum distributor which is supposed to be correct for an S. Minispares apparently do not list a dynamic advance number to use with a strobe, and I got no response from them when I emailed asking for a suggestion.

Like I said, too many variables. But I’m a little less panicked now thanks.

[mikal]

"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).

[iain1967s]

Changed from Millers W30 running-in oil to Agip All Guard 15/40 today, replaced the bimetal regulator with a solid state repro, and changed the temperature sender out with a NOS Smith’s TT-3803/00A which I think is correct for 1969 Cooper S. No time for a test drive today, but I’m due to take the Mini on a run tomorrow so will take a digital thermometer with me and see how it goes... Have to order the higher rating thermostat as not an off the shelf part here in USA.

ps. The “Cooper S standard cooling systems are marginal at best" quote was from CalverST website.

[zbarbera]

Can’t wait to see you Iain! Hopefully a bit better weather than the rain right now! Still looking a bit chilly though, so I suppose that’s good.

[mikal]

"ps. The “Cooper S standard cooling systems are marginal at best" quote was from CalverST website."

I think that is a rubbish statement from Calver. It clearly cannot be the case if the system can handle the very hot summer conditions we have in Australia. As I said before, I've never had a Mini overheat in 30 odd years of driving them here even when it's very hot weather. Spider, perhaps you can comment on this?

[Spider]

"ps. The “Cooper S standard cooling systems are marginal at best" quote was from CalverST website."

I think that is a rubbish statement from Calver. It clearly cannot be the case if the system can handle the very hot summer conditions we have in Australia. As I said before, I've never had a Mini overheat in 30 odd years of driving them here even when it's very hot weather. Spider, perhaps you can comment on this?

I'll hold back a bit here. The only time I've ever had a Mini or Moke run hot or overheat has been from a fault with the car or the cooling system, I can say it's never been because of some design error, this includes road cars to around the 100 HP mark, race cars to well over that, Mokes trudging through soft sand (where revs and loads are high, but speeds are very low).

The other times I've heard of issues, probably more so with Mokes is when the going is tough and there's a strong wind from the front left, though, I can't say I've experienced issues under these conditions.

My own Moke did run hot one day, heading North out of Birdsville one October, didn't overheat just ran hotter than normal. I think that is was 53 C outside had something to do with this, I did back off to about 90 kph. Did this hour after hour, all the way to Mt Isa about 680 km further down the road.



When I had my Mini business, apart from Tuning issues (mixture and / or timing incorrect), the next most common cause I found for overhearing was a rusty cooling jacket in the engine and / or choked radiator.

[iain1967s]

replaced the bimetal regulator with a solid state repro, and changed the temperature sender out with a NOS Smith’s TT-3803/00A which I think is correct for 1969 Cooper S.

Drove 100 miles today, mix of 55mph highway and 25mph suburban. Gauge went to 3/4 in the N range and stayed there, never went into H. I also measured the coolant, engine still running, with a digital thermometer immediately when parking up after the run. 86°C in the radiator tank.

So looks like this was just an electrical/instrumentation issue. Out of interest I'm going to bench test the NOS Smiths regulator, as wondering if it just passing through 12v instead of actually regulating to 10v.

[Dearg1275]

replaced the bimetal regulator with a solid state repro

Where did you get your solid state regulator and is it a recognised manufacturers offering?

D

[iain1967s]

Available here. I suspect the minispares "negative earth only" version is also solid state, as the original bi-metallic was polarity insensitive.

https://www.bpnorthwest.com/voltage-sta ... round.html

[iain1967s]

Hmm it happened again today. This time I had set the ignition timing with a vacuum gauge and the mixture was richer.

99.1°C measured with engine running after a two hour highway drive at 60 mph

May be time to look at the cam timing, but first I’m going to try straight water instead of Evans waterless, as spider suggested.

[Jim1071]

Took my 1967 S out for the first real run today since rebuilding the original engine.

Expected it to run a little hot due to things being tight etc. but the temperature gauge went right across to maximum within a few minutes of driving.

Lots of things have changed since it's last run [engine, fan, water pump, voltage regulator, wiring loom, radiator, temperature sender] so I don't really have any confidence that the temperature gauge is correct.

Thanks.

I know this sounds out there are you sure the radiator cap is correct ?
if you have installed a shallow radiator cap with a deep radiator cap rad...

that's what happened to my 1964 cooper s

Jim

[iain1967s]

are you sure the radiator cap is correct ?

Thanks for the suggestion, but it’s running waterless coolant so there is no pressure to be kept in by the radiator cap. It’s just there to stop the coolant sloshing around on corners

I did change the thermostat to a high flow 82° type instead of the 75° “Cool” version per Spider’s suggestion. Haven’t had a chance to take it out on a run yet though to see how it behaves.

[Spider]

are you sure the radiator cap is correct ?

Thanks for the suggestion, but it’s running waterless coolant so there is no pressure to be kept in by the radiator cap. It’s just there to stop the coolant sloshing around on corners

I did change the thermostat to a high flow 82° type instead of the 75° “Cool” version per Spider’s suggestion. Haven’t had a chance to take it out on a run yet though to see how it behaves.

Sorry to jump in here again, however, I doubt that the cap or the thermostat is the issue here, I'd strongly suggest it's the coolant itself.

If all is well, even with water in the system, a cap isn't needed. Pressuring the system by way of the spring loaded caps only serves to raise the boil point of the coolant, so if it's not getting up to boiling point, then there's no issues by not running pressurised. A good friend who after fitting a new Mini Spares Radiator and having it leak from the core a week later ran for a year with no cap as when it wasn't presuurised, it would leak much less.

A thermostat change, as I have suggested is in order I feel, however, that's only to give the system temperature stability when all else is in good order. If things are not right, which in the case, they are not, then this change will do nothing to fix that problem.

In this case, I keep coming back to the waterless coolant. There was a lot of good info in this thread on it and many people's experience from using it, including those you've described here;-

viewtopic.php?f=3&t=9939&hilit

[iain1967s]

Thanks Spider. I have a checklist of things to work through... I’m at step 2 currently

Main reason for trying the thermostat first is in case it’s restricting flow through the radiator.
Evans actually suggested flow rate is more important than temperature

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.