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coolant leak source and expansion hose replacement
I know another coolant leak post. I'm sorry! I searched the forum but can't find the posts I thought I'd bookmarked years ago.
First off, I noticed a coolant leak about a month ago that's gradually gotten worse. At first, it was just low coolant in the expansion tank but every time I fill it back up, it goes right back down after a drive. Didn't see anything initially but I found a big puddle of coolant drip on the garage floor today. (pictures attached) I'm afraid it's the thermostat housing but I'm not sure so just want to confirm. I've also had an intermittent thermostat sensor engine code (stuck open) the last couple years but it hasn't come on recently for about 6 months.
Anyway, just want to get some guidance on what I should replace... thermostat housing? water pump? other things? Links to any replacement guide posts would really be appreciated as I seem to be terrible at using the search function. (Are all the guides stickied somewhere?)
Second, whenever I do an oil change, the coolant expansion tank hose leaks a lot of oil coolant. A few years back I saw a post here about replacing the original short hose with an upgraded extended long hose to make oil changes easier. I can't find that post anymore but if someone has the part number for the extended hose I'd really like to change it out since I'm gonna have to drain the coolant anyway.
(I read elsewhere to page ECS Tuning Mike for help!)
I don't have extensive knowledge of car repair but I'm DIY and learning as I go along, so any tips appreciated!
Thanks everyone.
looking back from about midway down the middle. yellow at bottom is expansion tank. left is engine area. wet area below is transmission?
Last edited by HAMnMINI; Feb 26, 2024 at 05:04 PM.
Not sure if this is exactly the help you’re looking for but I’m currently fixing a coolant leak on my n16. I originally thought it was the water pump and after replacing that, it still leaks so it figured out it was the connection between the water pump and water pipe that comes from the thermostat housing. So if you can look at that joint to see if there’s a leak or some kind of build up that may help.
Not sure if this is exactly the help you’re looking for but I’m currently fixing a coolant leak on my n16. I originally thought it was the water pump and after replacing that, it still leaks so it figured out it was the connection between the water pump and water pipe that comes from the thermostat housing. So if you can look at that joint to see if there’s a leak or some kind of build up that may help.
Where was it leaking for you? The water pump is on the passenger side and my leak is dead center, leaking onto what I assume is the transmission housing.
I really hope it's not the water pump because I don't think that's something I can handle. Replacing the thermostat housing looks hard enough, but the thermostat is faulty anyway.
I would say so far, the water pump was easier for me(I’m still not done with the thermostat housing and water pipe) but it sounds like it might be the thermostat housing for you. But just speculation. Which ever you have to do, they’re both manageable just difficult and require patience.
Originally Posted by HAMnMINI
Where was it leaking for you? The water pump is on the passenger side and my leak is dead center, leaking onto what I assume is the transmission housing.
I really hope it's not the water pump because I don't think that's something I can handle. Replacing the thermostat housing looks hard enough, but the thermostat is faulty anyway.
Dripping down Front of engine is usually oil filter housing gasket leaking.
Pooling on transmission is usually the thermostat it self.
Pooling on engine and back side of engine near fire wall is the water pipe or thermostat where they meet.
Leaking down the passenger side of engine in back corner is mostly the water pump or waterpump/waterpipe connection.
Leaking down the front side of the transmission and not near the engine is usually the expansion tank on the bottom or the neck of the connection of the expansion tank.
Call around: chances are one of your local auto parts stores will rent you a cooling system pressure tester for free (typically you pay for it and then they refund you when you return it). Around here O'reilley and AutoZone will both do it. That's the easiest way to find leaks because you can just pressurize it with a cool system and look for where it's dripping.
You'll need the right adapter for the expansion tank but I think the Mini size is reasonably common and should come with the kit.
Dripping down Front of engine is usually oil filter housing gasket leaking.
Pooling on transmission is usually the thermostat it self.
Pooling on engine and back side of engine near fire wall is the water pipe or thermostat where they meet.
Leaking down the passenger side of engine in back corner is mostly the water pump or waterpump/waterpipe connection.
Leaking down the front side of the transmission and not near the engine is usually the expansion tank on the bottom or the neck of the connection of the expansion tank.
Thanks. When you say #6 in the diagram, which diagram are you referring to? All the diagrams I've come across are missing the hose attached to the bottom of the expansion tank.
Speaking of this hose, do you guys sell the extended version of this hose? I want to stop it from leaking when taking out the expansion tank to change the oil filter.
Also, is there a site I can check my VIN for factory extended warranty bulletins?
Per Vin and application you might need a thermostat adapter if its never been changed and original thermostat.
" Speaking of this hose, do you guys sell the extended version of this hose? I want to stop it from leaking when taking out the expansion tank to change the oil filter." No but we do have just that connection piece on its own. https://www.ecstuning.com/Search/Sit...h/11537600674/
Call around: chances are one of your local auto parts stores will rent you a cooling system pressure tester for free (typically you pay for it and then they refund you when you return it). Around here O'reilley and AutoZone will both do it. That's the easiest way to find leaks because you can just pressurize it with a cool system and look for where it's dripping.
You'll need the right adapter for the expansion tank but I think the Mini size is reasonably common and should come with the kit.
I took up your advice on testing with a cooling system pressure tester. Got one from AutoZone with the extended adapters. None of the adapters fit, go figure lol. But I managed to test it with the universal adapter.
As far as I could see, there was a stream trickling down from below the vicinity of the thermostat housing, dripping onto the transmission and then onto the floor.
I took up your advice on testing with a cooling system pressure tester. Got one from AutoZone with the extended adapters. None of the adapters fit, go figure lol. But I managed to test it with the universal adapter.
As far as I could see, there was a stream trickling down from below the vicinity of the thermostat housing, dripping onto the transmission and then onto the floor.
Sounds like you need to make plans to change out the thermostat and crossover pipe
you might need a thermostat adapter if its never been changed and original thermostat
Just want to verify which adapter for production year 7/2012?
Originally Posted by njaremka
Sounds like you need to make plans to change out the thermostat and crossover pipe
Why do you recommend the crossover pipe if it's only leaking down the front of transmission?
I wouldn't mind changing out the water pipe but it looks crazy difficult having to do it blind. I couldn't even see where you'd need to unclip it without removing the intake and manifold.
You can unclip the thermostat from the pipe without removing the manifold. That's what I did to change mine. Best to have the pipe in hand when performing the work, since the pipe is difficult at best to replace on its own. You have to remove the thermostat to replace the pipe.
Sorry I meant how would I unclip the water pipe? It's pinned in the middle below the manifold. How do I access that pin without having to remove the intake and manifold?
I can't seem to find this stated anywhere but what exactly is the difference between the old and new thermostat that requires new adapters? Are there two ports on the harness to plug into or is there another adapter needed to join them?
Just want to verify which adapter for production year 7/2012?
Why do you recommend the crossover pipe if it's only leaking down the front of transmission?
I wouldn't mind changing out the water pipe but it looks crazy difficult having to do it blind. I couldn't even see where you'd need to unclip it without removing the intake and manifold.
I did my thermostat in fall 2021 (I think) with coolant appearing on the transmission being the clue that the thermostat had gone. I had planned on replacing the crossover pipe anyway and it broke coming out. I replaced it with a cheap aftermarket that might have the name "flex" in it. That started leaking at the thermostat end about 15 months after the first fix so a few months back I replaced that with the metal ECS one which isn't much more expensive than MINI's plastic pipe. You can push the pipe in under the intake manifold from the thermostat end. Some remove the manifold but that's whole lot more work.
Several weeks after replacing the thermostat and pipe in 2021 I noticed a coolant leak at the water pump end and so was second guessing my initial repair but it turned out to be the water pump. It's a coolant conspiracy I tell ya!
You're in there so replace the crossover pipe otherwise the coolant conspiracy ghosts will get you!
Update: This weekend I took out the air intake, intake manifold, thermostat, and water pipe. Taking out the intake manifold is mandatory to avoid breaking the water pipe (and finding hidden ties) so the guides really ought to put in that disclaimer. However the intake manifold is a pain to take out and took me like 6+ hours. I've come across 4 or 5 different r56 design setups for thermostat + intake + manifold and all the available guides are pre-2012 centric so I had to figure it out myself as I went.
Anyway, following up on the thermostat adapters, my thermostat has 1 sensor. Then a coolant hose has another sensor. Since there are 2 sensors on the new thermostat that matchup with the 2 plugs on the existing electrical harness, that leaves the sensor on the coolant hose unconnected. Does this require another adaptor or does it remain unused? (see plug marked "h" in pictures)
thermostat with one sensor manufactured 6/2012 sensor marked "h" unused with new thermostat setup
That metal elbow is an older design.......you can eliminate that by getting a new hose .......that's what I've done
to mines.......unless you just want to leave it.....that sensor is no longer used the new thermostat has them now....
Also, the thermostat housing is made by Markiv as well. I don't see any cracks on the thermostat housing; I think what actually failed was the gasket wearing out. The thermostat itself has been finicky for a few years so I needed to replace the housing anyway. Just not sure about water pipe.
I am running our bremmen parts thermostat and the ECS metal water pipe.
My Genuine MINI thermostat went and leaked onto my transmission. It had a hairline crack and when the car go warm it would leak.
Do you know who makes the genuine MINI thermostat housing? I read posts here saying the bremmem one started leaking and they had to replace it with a genuine one so idk anymore lol
