I can see coolant on top of my transmission and it is obvious something sprung a leak. However, when I put water in, nothing looks to be pouring back out at this point. Honestly, I can't get any distilled water because of the friggen corona virus.... So, it is making things hard. However, I can't see anything that is obvious like a gapping hole in hose or water pouring out of the housing.

So now I'm into guessing, I would say the car overheated and overheated water came out of a number of rubber hose fittings in and around the thermostat. So it got me to thinking what are the symptoms if the water pump was no longer pumping or barely pumping, water and the car overheated. The water/steam has to go some where. Is it possible it just came out everywhere near the thermostat including multiple hose fittings without the thermostat necessarily obviously failing?

On most cars, when the water pump fails, the common failure point on the water pump is/are the bearings. The bearings fail and water leaks out around the water pump bearing on the pulley. However, the water pump on the mini is pretty much a sealed unit so when it fails, how does it normally fail?

Any pictures of failed water pumps so I can see the common failure weak point? Does the plastic inside belt? Is it just the weird system that drives the pump fails, but the pump is fine?

 

The cooling system works under pressure with coolant temperatures above the boiling point of water.
My wife's Mini only lost water when hot. Culprit was the water pipe connection on the water pump side. Tested fine with the pressure tester when cold.

Yours is probably a crack in the thermostat that only leaks water under pressure and then drops onto the trans.

Try a pressure test (get a power bleeder; great for brakes and testing the coolant system), or may just slap in a new thermostat and water pipe. Go the long way and get the pipe changed out as well.

 

I had a car with a pinhole in a hose. It would leak in a jet stream only when hot. It was a head scratcher, I only found it by observing when hot.

 

First, the water pump is on the opposite side of the engine from the transmission, so it is likely not the water pump. The thermostat is on the side with the transmission, and so are a number of other hoses. My suggestion is to get the car up to operating temperature, and then poke your head around that area. It might become obvious where the leak is once the car is at temperature.

 

Yes, I agree this is the "minimum" I will probably do. However, if the real issue is the water pump not creating movement in the water so as to keep the water cooling in the radiator, then I will not really be fixing the real problem. So in essence I'm trying to determine not just if I need to fix the thermostat and the pipe but the water pump as well? It depends on "what" the common failing point is on the water pump. If it is the bearings like most water pumps, then I know that is the case with mine as that is a very "noisy" event.

 

Hmm, the problem is I had to take everything out just to see stuff. I was not able to see the problem with the car at temperature because everything is so buried.

 

The Power Bleeder looks expensive. What about this? This looks like it might work but I would need a way to adapt an inlet into the system or maybe trash a cap? I have a compressor as well that I suppose I could just set to some kind of pressure.
https://www.ebay.com/itm/Hand-Held-V...8AAOSwr9ReavFv

 

My thermostat did this and I guess the water pump if its the old plastic version can do that also, mine had a slow drip that got worse. They crack at the bottom. New ones are metal.

https://www.northamericanmotoring.co...8-no-heat.html

 

My coolant tank split apart at the seams. We couldn’t find it till we pressurized the system. I had coolant on transmission and everywhere else in the front corner.

 

A water pump not pumping is not a common failure. This requires either the belt slipping or broken/missing, the shaft breaking, or more likely but still rare is the water pump developing enough bearing play the impellers contact the block and are broken off. This is a risk with those water pumps which have a composite plastic impeller.

The usual signs of water pump failure are a coolant leak or noise.

Not with my Mini but with other cars I have had cars with both types of failures. With one the water pump became noisy at 172K miles. At first I was not sure where the noise was coming from. But since it was present from a cold start I removed the serpentine belt and started the engine and let it idle only long enough to conform the noise was not present.

I then checked all the accessory drives for bearing play. Only the water pump had any. It was not much but any is not good. Also, the inner edge of belt was worn from contact with at least one pulley which is a sign the belt is not tracking which arises from excessive bearing play which lets the pulley move out of alignment.

Buttoned everything up and called for a flat bed tow truck to haul the car 25 miles to the nearest dealer for a new water pump, T-stat, and fresh coolant.

With another car I smelled the strong odor of anti-freeze from a hot engine -- not overly hot just fully warmed up. In this case I dashed to the nearby dealer and with the car on the lift there was leak sign at the water pump. Mileage was around 100K. Had a new water pump, T-stat, fresh coolant done and that was that.

 

What is the pressure you need to test it or the maximum the system can handle?

 

I honestly can’t answer this for you, I wasn’t there, and I didn’t have the scan gauge at the time to check temps. I filled tank up drove it home 10 minutes and let it sit, then once mechanic was ready, filled up and drove 3 minutes down to him. Mechanic had to order the right cap for our tanks so we could pressurize it and he did it while I was at work, he couldn’t wait, he isn’t just my personal mechanic. I really hope someone else can chime in and help

 

I suggest getting the Bentley manual. I believe testing pressure is 20psi. I didn't loose pressure, but still lost coolant; so just keep in mind that this test may have false negatives.

For testing I'd​​​​I'd suggest getting the motive power bleeder. That you can use to also bleed your brakes (and has some resale value). The adapter for the Mini fits on both the brake reservoir as well as the expansion tank.

 

Yes 21.8. I found this article. https://www.pelicanparts.com/techart..._Leak_Test.htm

 

this is good to know, I want to swap brake fluid, and I know they have what is needed. Thank you.

 

So is the cap size of the master cylinder and reservoir the same (45 mm?).
Then this would work as well maybe?https://www.ecstuning.com/b-schwaben...0aAtwgEALw_wcB