Lee’s Mini Prep – cooling

Porkpie 2019……..are you ready?!


If you are reading this then congratulations on entering arguably the best car based adventure in New Zealand. The trick now is making sure that your mini is up to the task!


For all you repeat offenders I’ll apologise in advance for trailing out this info again…….it seemed to work last time as there were very few breakdowns compared to previous runs! For all you newbies please take heed of these few simple checks to get your minis in top shape. This will make the run for more stress free, from a mechanical perspective at least. If you need any further help you can contact Minibitz on 09 837 0040 or email [email protected]


For owners of new MINIS your vehicles should be more than up to the task. Naturally you will need to make sure your cars are serviced and check fluids etc during the course of the trip. Please excuse my lack of further preparation info for you, but quite frankly I don’t think your cars will need it…..which is a good thing!


For all participants in classic minis you are about to take what is now an antique vehicle and in a little over one week travel more than 5,000kms from the top of the North Island to the bottom of the South. Along the way we will encounter gridlock leaving Auckland (it’s Easter Friday so everyone will be trying to exit the big smoke), central plateau chills, undulating hills of the Paraparas, South Island alpine passes and wet west coast forests.


What does this mean for your mini? You will need a top notch cooling system, well adjusted brakes, bulletproof ignition system and a well tuned carburettor.


Also consider we are travelling over a holiday period so workshops & car part stores will not be open should your mini run into troubles. For this reason it will be wise to carry tools and enough basic spares to keep you on the go should problems arise.


For Tracey and myself this will be our 6th trip. On the previous 5 runs there have been a few common problems. Mostly due to lack of preparation and servicing. With so many cars signed up this time around I thought it might be helpful to knock up a few articles on some of the basic mechanical issues encountered by participants on previous runs and how to prepare your minis for maximum reliability and enjoyment on your adventure.


So, to get the ball rolling let’s start off with the single most troublesome issue encountered on previous runs………


The Mini Cooling System


First thing to check is that the cooling fan is fitted the correct way around and is in good serviceable condition. This is the single most common cooling system mistake we see in our workshop but ironically the last thing people ever think to check. All plastic cooling fans are marked showing the side that should face the engine. See the image below


The reason for this is that the blades of the fan have an aerofoil shape. The fan rotates in an anti clockwise direction pushing air through the radiator and out through the passenger side wheel well. Having the fan fitted back to front places the aerofoil on the wrong side, greatly reducing efficiency.






Next thing to check is the overall condition of the fan blade. The two pictures above show a new fan along with a typical used fan. You will see that the new fan has nice straight blades and in picture 1. you can see the aerofoil shape I mentioned before.  My hand is on the radiator side of the fan. In comparison the old fan pictured has blades that have started to curl due to heat and age. This has caused the blades to lose their shape, which has quite an effect on efficiency. In some instances we have measured a difference of over 10 degrees between new and old blades.



Next check is the radiator cap. There are two main types of cap required to suit a mini radiator. Fitting the incorrect cap is a common mistake and can lead to loss of coolant and overheating issues.


Most minis will run a closed cooling system. This requires a cap that seals the radiator, preventing coolant from overflowing. On this type of system the radiator needs to be filled to about 15mm below the filler neck. The correct cap to use is the one shown on the left above. It has a single rubber seal at the base. After topping up the radiator any excess coolant will be pushed out through the overflow pipe once the engine reaches temperature. After that there should be no coolant loss.


The other type of system used on more modern minis such as 1990’s fuel injection models utilises an expansion tank fitted under the passenger side guard. On this setup the radiator is filled to the top. Any fluid expelled due to expansion is then pushed into the expansion tank. As the engine cools coolant is drawn back from the tank into the radiator. This cap is shown on the right and has two rubber seals. These caps are often marked on top with the word “recovery” but not always, which is why I have mentioned the seals as a way of checking you have the correct cap.


Fitting a recovery style cap to a sealed system will be problematic, as it will allow coolant out of the overflow pipe. With no recovery tank that coolant will be lost. This leads to a low fluid level in the radiator so check you have the correct cap fitted. Don’t rely on your local counter guy at Repco to select the correct cap, as they don’t have a clue and 90% of the time will supply you a recovery cap which is wrong!


One exception to the above and an issue we saw on a car last run is the older 850 style radiators. These run a sealed system but have a deeper filler neck, so neither of the above caps will seal this style radiator, although they both seem to fit! A deep neck cap, sealed system cap will be required.


I would recommend fitting a new thermostat prior to the run. They cost very little, are easy to replace and it’s a guarantee that the coolant can get to the radiator once the engine is up to temperature. A trick for any of you running A+ engines with no bypass hose between the cylinder head and water pump is to drill a couple of 1/8” holes around the edge of the thermostat. This will allow coolant to circulate through the head prior to the thermostat opening on this model engine.


Check that all hoses are in good shape. Change any that look suspect and put on some fresh hose clamps at the same time. Makes life much easier should you need to remove any hoses on the run!


If you have a pre A+ engine with a bypass hose between the head and water pump it is advisable to fit a piece of ½” heater hose rather than the concertina style hoses available. The quality of the concertina type has been very poor the last few years with them often failing quite soon after fitment. You will need to remove the water pump to fit one of these but it will be worth the effort and last for a very long time. We use silicone hose for this purpose which is very durable.


Check the condition of the radiator. Look inside and check that the tubes are not blocked with crud. If they are it will need to be professionally flushed or replaced. Sticking a hose in the filler neck will not be sufficient to clean out a blocked radiator. A professional flush requires the top and bottom tanks to be removed so the tubes can be cleaned out thoroughly. A new copper core radiator weighs about 2.3kg. I often find that old radiators we remove from cars weigh quite a bit more as they are full of silt and deposits. A radiator we removed last week weighed 2.8kg so had 1/2kg of crud inside. Not a scientific check but an indication that something is not right. New radiators are not too expensive and it’s often cheaper to fit a new one that get an old unit repaired.


Water pumps. These usually only need replacing if the seals inside give way or the bearings fail. Most pumps have a drain hole so when the seal quits water escapes. Fairly common fault so keep an eye out. We like to fit pumps with solid cast iron impellors like the factory style pump. Most parts suppliers in NZ sell pumps with pressed steel blades. Water tends to cavitate in these pumps so they are not ideal. The blades on these pumps can also rot out so beware.


Make sure to have some antifreeze in the cooling system. This is a corrosion inhibitor and will keep the inside of the block, radiator, pump etc free from corrosion.


Lastly … fan belts. Very cheap, so just fit a new one and make sure to tension it correctly. As well as keeping the engine cool this will also ensure that the battery charging system is being topped up.


If you need any further advise or help with parts mentioned above we keep them all on the shelf and will be happy to assist with fitting also if mechanical work is not your thing. Feel free to give us a call on 09 837 0040 or email [email protected]


All the best with preparing your mini and fundraising.


Until next time…..






You may also like...