Mini Cooper Cooling Testing

[carockwell]

This thread is for the original Mini that was discontinued in 2001. The early Mini's used a side mounted radiator that fit in the left side wheel well. Air enters through the front of the car , takes a 90 degree turn and is pushed through the wheel well by an engine driven fan.The Mini has always been known for a poor cooling system. What series of tests can I perform to pinpoint the problem with this car's cooling system? Also, what is the best way to measure a pressure drop across a radiator?

 

[GregLocock]

1) Dunno, I'd try and measure the airflow (and direction) and waterflow and the top and bottom hose temperatures in a variety of operating conditions.

2) A water tube manometer

Paging evelrod

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[ahbugeye]

When we had a coolant problem with our classic mini, we first tried replacing just the thermostat. that didn't work, so we replaced the radiator, thermostat and the water pump. Might as well do it all at once while you go that radiator out - there isn't much room to work! Our problem was the water pump, but just replaced it all since we had to take out the radiator to get to the water pump.

Good luck!!

 

[evelrod]

The Vintage Mini racing community has about a 'zillion' "cures" for overheating, none of which I am totally in agreement with. Most ideas include auxiliary radiators and such, not a bad idea, just a 'clumsy' idea. I'll tell you what I use on my racing 1963 1380cc Austin Cooper(~135hp @ 7600 rpm with a CR of 13.87:1) that weighs in at 1385 lbs. dry---Also it has NEVER overheated (knock wood) even in a two hour race at Willow Springs where the air temp was ~105f degrees!!!

I use a "Two Core" rad sold by MiniMania, stock replacement with the stock fan shroud. Fan is the 11 bladed yellow plastic fan---I once tried the OEM "tropical" fan and it seemed to work almost as well, but it's metal and heavy. I switched to the "high output" water pump with stock diameter pulleys. I have routed the heater outlet at the back of the cylinder head to the radiator tank via a 3/8" hose (to aid in cooling the #4 exhaust valve). I alternate between a 180f degree thermostat and a "blanking sleeve" to slow the water return to the rad and help prevent pump cavitation.
I use a 19 row (too big for street use) oil cooler with a remote mounted racing oil filter and a 3 qt. oil accumulator for a total oil capacity of 10 qts. (this is in no small way responsible for added cooling capacity). All this works for me, but is obviously not totally suitable for street use.

For my brief time with a street Mini, I used a "four core" radiator (hot setup at the time) that did NOT work all that well---"Two Core" along with the OEM 'tropical fan' was much superior in cooling. I did use a smallish ex-Sprite oil cooler---seemed ok on the streets and freeways of Southern California in the summer where temps in my area are often 110f and more.

When I hear of major overheating problems with Minis (all too often it seems) I first question the quality and condition of the radiator. You cannot use one indefinitely without service to clean out deposits, etc. Properly cared for, many older rads will work "forever" (My 30 Ford rad is still going strong), but many of the newer replacement parts are inferior in quality and construction, thereby limiting their ability to cool sufficiently, IMO. Stick with the basics, quality parts from trusted vendors and you will usually be ok.

Two additionl comments---Always use a fan, the bigger the better, IMO. The side mounted rad needs the fan to get the airflow pointed in the proper direction. It has been proven in racing Minis that a "remote filler tank" in the cooling system will prevent coolant loss and thus prevent overheating from that cause. Mine is mounted on the fender inner panel and is connected to the rad by the standard overflow hose. I use a 7 lb. cap on the rad and a 15 lb. cap on the remote tank. The overflow from the remote tank goes to a one qt. plastic bottle via a small dia plastic tube (no coolant has ever made it that far, at least not yet)!

http://www.miniamania.com

http://www.minispares.com

http://www,calverst.com

http://www.pegasusautoracing.com

http://www.mincompracing.com

http://www.heritagegarage.com

Some vendors offer aluminium radiators, I haven't tried one yet, but the guys that use them swear by them. Kinda pricey but I want to try one if my situation ever changes. Like I said before, "don't fix it if it ain't broke"!

Rod

 

[carockwell]

Kind of impressive that you can keep your Mini cool at 110 degrees F. This thread was meant to get at the basic engineering problem with the side mounted radiators, not so much to learn what parts will keep a Mini cool. I had been thinking that the problem was either insufficient pressure drop across the radiator, or that the radiator was inhaling preheated air from the exhuast. The newer two core radiators themselves are fairly large compared to a Honda with twice the power and 40% more displacement.

 

[evelrod]

Well, I'm not alone. Most all my competitors don't overheat either. I would suppose, then, that as it relates to your questions, the fact that most of the Mini owners out here in Socal manage to keep their cars from overheating, using mostly OEM parts and technology doesn't mean all that much. Best of luck in you quest.

Rod

PS: Honda? Is that one of them thar Japanese cars?

 

[patprimmer]

When relatively new, over here in Australia, Minis never had an overheating problem on a well maintained car.

I expect BMC at the time tested here and developed "tropical" or heavy duty parts before release.

We have quite a hot climate in most areas.

Once again, Rod Is Right. I would take serious heed of his advice.

Regards

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[carockwell]

Ummmm..I live in SoCal (Newport Beach), lots of people don't drive their Minis around on the street when it gets hot.

 

[Peter7307]

Another ex Mini owner here too. There are more about then it might be first expected.

To the cooling challenge..
One other point is the Mini vents the readiator air into the LHS wheel well which can allow a build up of road debris to coat the radiator thus reducing heat transfer.

I have to agree with the comments by patprimer above...well maintained Minis here rarely had any oveheating problems.

Author David Vizard's book "How to modify your Mini" holds a lot of information on this subject and is well worth seeking.

Cheers,Pete.

 

[romke]

the mini cooling system was indeed a system that was prone to overheating, frequently due to partly blocked radiators and or faulty pressurecaps that prevented adeqaute pressurizing the system and thus reducing the heat carrying capacity of the coolant.

i used to employ an agressive cooling system cleaner once a year to get lost of the blockage and also used a pressure cap with a somewhat higher setting. that cured most of the problems, but not the original design deficiencies...

one additional item might be the fitting of an electric driven high capacity fan. my mini usually overheated not when driving at high speed, but when idling for prolonged periods of time after a fast drive. under those circumstances the engine driven fan does not give enough airflow through the radiator and heat may build up. a thermostatically driven fan that becomes active under those conditions made a big improvement.

 

[evelrod]

romke.

...cooling system was indeed a system that was prone to overheating, frequently due to partly blocked radiators and or faulty pressurecaps that prevented adeqaute pressurizing the system and thus reducing the heat carrying capacity of the coolant.

Show me a car that WON'T overheat under those conditions!

carockwell.
It gets hot in Newport Beach? The folks up in Costa Mesa around Heritage Motors and Mincomp seem to manage the "heat" without undue stress! ;-)

Rod

 

[carockwell]

Ummm..Heritage? They are the ones telling their customers not to drive when it gets over 90 degrees, along with Don Racine at Mini Mania.This thread was not intended to be a discussion about who's car, or who's equipment works best, but about how to take measurements to arrive at the definitive "problem" with the side mounted radiators. If you don't have a problem with your car, great.If you don't think there is any problem at all, that's good information.So far, I think that some cars have a problem with the pressure drop across the radiator, or that hot air from the exhaust gets sucked into the radiator, or both. It definitely varies from car to car, and it definitely is not ALWAYS cured with an 11 blade fan, or the modern two core aluminum radiators, or by cleaning the radiator from road debris, or all of the above. The radiator is actually larger than an old Honda CRX with twice the power, but that radiator faces forward.

 

[GregLocock]

Perhaps I ought to clarify - in my original answer the water tube manmeter was to measure the airflow resistance of the rad, not the internal pressure drop, which will be much larger.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[evelrod]

I agree that there are cars that overheat for various reasons. All I'm saying is that in the case of the Mini it is NOT a design problem. My initial experience with a Mini Cooper was in 1964 in El Paso, Texas where the temp was around 100f degrees all summer and I recall no overheat problems. As to Heritage, I'm curious as to the source of your information. You did not hear that from Graham as he drives his Mini all year, rain or shine.
I've only spoken to Don R. once in 2003 at Las Vegas where we were racing each other and my crew was helping fix his car's overheat problems due to a broken fan belt pulley (temps were in the low 100's). We got him on track, but, during the flag race, I saw him off course "steaming". I did not get a chance to determine his problem as they had loaded up and left the track before the end of the race. I suspect it was the pulley again (toothed belt type).

As to airflow, I'm in agreement that the side mounted rad is in probably the worst place that I could think to put it...then again, considering all the extra room in the engine compartment <grin>, where else could you put it?
When I was tinkering with airflow underhood, I blocked the grill to see what would happen...airflow was from under the front valence up across the front of the engine to the bonnet and then it would "spread out in a flower like pattern" missing the rad altogether...thus the "11 bladed fan". Of course I did not leave the grill opening closed, but it did give me some insight into what I needed to do to properly duct in my radiator (left wheel well) and oil cooler(right wheel well). As I said before, so far no problems, even with summer track temps at California Speedway and Willow Springs in the low 100's. My water hangs in around 200f and oil at about 190f on those days. I'd like to see the water a little cooler, hence the desire to one day try one of the aluminium radaitors.

I'm not sure how comparing a Honda to a Mini is valid. One is a modern thin wall casting design of the 1980's and the other is an antique design of the 1950's (actually the engine design goes back to pre war era)...apples and oranges.

I'm not trying to "pick a fight" here, but I see your quest for info as simply an academic exercise. Am I correct?

Rod

 

[patprimmer]

A non ambiguous question is a good starting point to get clear concise precise answers on the topic you want.

You did include in your question that

The Mini has always been known for a poor cooling system

If you make a statement as a presumption that it is the cause of a problem, and others have evidence to the contrary, then correcting your inaccurate presumption is an appropriate answer.

and

what is the best way to measure a pressure drop across a radiator?

There are 2 pressure drops across a radiator. One person took the trouble to accurately answer one possible meaning.

Re the guy at Heritage, just maybe he gave you good advice, you did not understand or heed, so he decided that in your case, there would always be an overheating problem, so he gave an answer appropriate to you.

Regards

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