9 replies to this topic

[NLinPEN]

My Japanese (JDM) Mini with SPi engine has a non-standard coolant overflow tank installed. Something must have gone wrong with the original tank, and a previous owner decided to improvise something. I think that this improvisation isn't working. It is a overflow tank, mounted under the left fender, near the wheel. Held in place with a piece of metal wire to the side of the charcoal canister. It is mounted higher than the top of the radiator. And it is empty ...

 

My request: I don't know how the original expansion tank looks like, nor where it lives in the engine bay. Can someone who has the original tank installed please take a photo of it in the engine bay and post here?

Such a photo could, hopefully, help me to create a better solution than what's currently in the car. It would be great if those original expansion tanks are still available.

Edited by NLinPEN, 13 February 2025 - 03:10 PM.

[mab01uk]

The later Rover Injection Minis have a plastic expansion tank for the cooling system in the nearside wheel arch on the inner wing. It is positioned up on the shock absorber/damper mounting bracket.

Discontinued in UK but now available again in link below from Classic Minis Japan.

Classic Mini Expansion Tank:-
https://classicminis...expansion-tank/

 

 

 

Edited by mab01uk, 13 February 2025 - 03:21 PM.

[genpop]

Your construction seems to be okay but the cooler closure may no longer work correctly. Buy a new cap and slowly overfill the radiator for about half a liter of cooling fluid. If you slowly fill the liquid into the Radiator it will drain to the expansion tank.The expansion tank should be half filled!

[viz139]

The main problem with this system is usually the radiator cap (wrong one fitted or rubber perished) .The cap is unique to this system as it has two rubber seals.

https://www.somerfor...-expansion-tank

 

Second problem is the bottom of the tank fills with sludge and blocks the inlet/outlet pipe, remove it for a good clean.

When reinstalled half fill it through the radiator overflow tube, slow process.

To check if your system is working properly open the rad cap when engine is cold. The coolant should be at the top of the rad. If there is an inch or so of air in the rad (like older minis) the system is not sealing .

[NLinPEN]

Thank you all kindly! I am learning here every time I am posting a question.

(1, mab01uk) The improvised tank in my car might be in the correct position, looking at the photo of where that expansion tank is supposed to sit. Similar as shown in the photo is it at the same height as the charcoal canister.

(2, genpop) I tried that method but the water would not go into the overflow tube, but instead went over the edge of the radiator. I guess I would need to take the overflow tube off from the radiator and then "push" some fluid into the expansion tank. That would also serve as a test to see whether that tube is blocked.

(3, viz139) I will verify whether the radiator cap is specified for 16 psi (haven't looked at that yet; I hope it has a marking). I understand your recommendation to fill the expansion tank via the overflow tube. I have a large syringe that I can hook up to it to transfer coolant.

(4, viz139) Some time ago I checked and noticed that the coolant was not all the way up to the radiator cap. I topped it up at that time. I would need to check again whether it is still full. If not, that would hint at the system not sealing, as you describe.

[NLinPEN]

Some updates/progress I made today:

(1) I forgot to check whether the system is sealing: I drained the coolant water before checking its level. That's a pity.

(2) I undid the hose from the radiator to the expansion tank. Then used a large syringe to get some water into the tank. This worked, without leakage. I noticed however that the water would not drain if I left the tube were it is. I had to bring it to a (much) lower position to get the water out of the expansion tank.

(3) The radiator cap is of the correct type: with a spring and rubber seals and a tiny hole in the center when the pressure becomes too high (see attached photos). However, I am not sure if it is rated for the correct pressure: it reads 88 kPa, which is about 13 psi. That's a bit lower than the 15 (or 16?) psi that I see on the vendors' websites.

(4) I now know that the radiator fan switch, plus rubber seal, is prone to leaking. I can well understand that aftermarket radiators nowadays have a screw-in type temperature switch at this position.

 

New/additional question: at what temperature is the radiator fan switch supposed to close? I held it in hot water (hot, but not boiling) but the switch did not close. I wonder whether the switch is good, and my measurement is bad, or that there's something wrong with the switch.

Attached Files

•  CapTop.jpeg   51.28K   1 downloads
•  CapSide.jpeg   42.87K   1 downloads

Edited by NLinPEN, 15 February 2025 - 10:08 AM.

[hungdynasty]

Some updates/progress I made today:

(1) I forgot to check whether the system is sealing: I drained the coolant water before checking its level. That's a pity.

(2) I undid the hose from the radiator to the expansion tank. Then used a large syringe to get some water into the tank. This worked, without leakage. I noticed however that the water would not drain if I left the tube were it is. I had to bring it to a (much) lower position to get the water out of the expansion tank.

(3) The radiator cap is of the correct type: with a spring and rubber seals and a tiny hole in the center when the pressure becomes too high (see attached photos). However, I am not sure if it is rated for the correct pressure: it reads 88 kPa, which is about 13 psi. That's a bit lower than the 15 (or 16?) psi that I see on the vendors' websites.

(4) I now know that the radiator fan switch, plus rubber seal, is prone to leaking. I can well understand that aftermarket radiators nowadays have a screw-in type temperature switch at this position.

 

New/additional question: at what temperature is the radiator fan switch supposed to close? I held it in hot water (hot, but not boiling) but the switch did not close. I wonder whether the switch is good, and my measurement is bad, or that there's something wrong with the switch.

 96 spi coolant switch.JPG   28.96K   0 downloads

 

Switch on at 98'C, off at 93'C.

 

(3) I've been using a 13PSI(0.9 Bar) cap for ten years since I bought the car, no problem so far.

(4) My car has a minispares screw-in type switch radiator, never leak at the switch. I put some anaerobic gasket sealant when install, certainly help.

[NLinPEN]

Thank you hungdynasty, I must have overlooked that specification in the documents. The hot water I used during the switch test was certainly not that close to boiling to be able to reach that switching temperature. And thank you for confirming that this cap should work just fine.

[hungdynasty]

Some updates/progress I made today:
(1) I forgot to check whether the system is sealing: I drained the coolant water before checking its level. That's a pity.
(2) I undid the hose from the radiator to the expansion tank. Then used a large syringe to get some water into the tank. This worked, without leakage. I noticed however that the water would not drain if I left the tube were it is. I had to bring it to a (much) lower position to get the water out of the expansion tank.
(3) The radiator cap is of the correct type: with a spring and rubber seals Android a tiny hole in the center when the pressure becomes too high (see attached photos). However, I am not sure if it is rated for the correct pressure: it reads 88 kPa, which is about 13 psi. That's a bit lower than the 15 (or 16?) psi that I see on the vendors' websites.
(4) I now know that the radiator fan switch, plus rubber seal, is prone to leaking. I can well understand that aftermarket radiators nowadays have a screw-in type temperature switch at this position.
 
New/additional question: at what temperature is the radiator fan switch supposed to close? I held it in hot water (hot, but not boiling) but the switch did not close. I wonder whether the switch is good, and my measurement is bad, or that there's something wrong with the switch.

Here is my modified overflow tank setup, I wasn't able to use the factory overflow tank after I change the shock brackets, so I relocate the overflow tank (with a new bottle)behind the grille, and I use a transparent hose to connect to the radiator so I can see if coolant is sucked back to radiator, easier to see if coolant is always full in radiator.  IMG-20250216-WA0064.jpg   69.38K   1 downloads
 IMG-20250215-WA0074.jpg   38.43K   2 downloads

[viz139]

The water dose not flow out of the expansion tank it is sucked out by vacuum caused by water cooling. This is why it is so important that the system is sealed properly and why this radiator cap has two seals.