Hey folks! I have an 05 S with 35k on the odom AND the slowest coolant leak I have ever seen! So slow in fact, I cannot find where it is going! Yet at periodic monthly check ins with the reservoir I find a need to add more again! I have checked the oil and it is as dark as can be. Now what? Any experience with this or advice? I am looking to add a 15% pulley, plugs, belt, before winter hits. Thanks, Jeff

 

So many different locations to be losing coolant from no real answer as to which one it is.

Common areas are: thermostat, water pump, cracked expansion tank, or if you're lucky the head is cracked around the headbolt nearest the timing tensioner.

We're also in Michigan, and would make for a great trip out to see us and give the car a proper look over and best advise you on what to do first.

Let us know how we can help, we carry near anything we'd need to fix your car same day, as well as go fast goodies!!

 

Try putting some UV dye in your coolant and looking for it with a black light. I'd like to hear how it works.

 

Dark as can be oil? How many mile since the last change?

 

Do the UV dye thing, and then make sure to check the oil-to-coolant heat exchanger!

It's hard to see from the top, but if you look on your oil filter housing underneath the filter canister itself, it's on the bottom side with 2 coolant hoses sticking out. Might have to take off the belly pan and look it from the bottom on the passenger side.

Mine actually broke, putting oil into my coolant, but you might just have some old o-rings in there.

Pretty easy to do yourself, as long as you have the right torx bit, an extension, and a swivel attachment!

 

I think I will give the dye trick a go first. Nick, I am planning on doing the supercharger pulley upgrade, but want some hands on exp. with it too. What do you charge for the job?

 

We charge $450 parts & labor for the pulley kit installation.

I'd still recommend giving the car a good look over while up in the air. If you have or can borrow a coolant pressure tester you can pressurize the system and let it sit for awhile to see if you get any drips or loss of pressure.

 

One tip...
Look at the edges of the radiator....
The plastic tanks on the side are just heat set (plastic welded, aka,melted) to the aluminum core....
After a few years the expansion and contraction of the metal and plastic can cause leaks, and the plastic gets brittle, and can firm cracks ..
Fix is a new radiator....but they can be found online for $100-200 in various brands....most OEM look-a-like are fine and are sold by the big box parts stores or rockauto pretty cheap.

 

Thanks for the tip!

 

Ive inspected the whole front end of the car and cannot find anyplace that looks aged or broken/cracked. Its such a slow leak that I was worried I was going to find milky white oil. But nope. Which is good. But, I need to find the bugger anyway! So step one, i will clean the engine compartment out really well and try the dye over this weekend. If I still get no results, then find myself a coolant pressure tester.

The pulley upgrade can wait til I get this ironed out, but I plan to get it installed before winter hits hard here in western michigan.

 

Sometimes chasing a ghost can drive you nuts....
You might just consider keeping a quart of coolant next to your quart of oil....and checking them both at the same time for a few months, while you wait for the issue to progress....
A pinhole leak can sometimes persist and be very hard to find....and cost more to find than the $$ it could ever damage if you retreat to a "watchful WAITING" postion....

 

you can also check the heat exchanger, if you don't use your ac or hvac it can be a slow leak, but would definently consume more coolant when you do use it. the floor could be slightly damp

 

Have you looked at the plastic T-connector behind the thermostat housing? Its down below the air filter box towards the back. It is a standard coolant line with a T-connection, the T-connector leads back to the coolant expansion tank. The small tubing is known to snap/crack over time.

Pics from my exercise:

Old vs New


Pic is fuzzy but follow my fingers back to the gap in the coolant line


New connector installed and everything secured


Part Number if need be… 17127518614

REALOEM WEBSITE LINK

 

There's yet another remote possibility that you're over-filling the reservoir. The correct fill level is just below the "ribs" you see in the bottom of the reservoir.

 

A bad scenario is the head gasket is leaking coolant into the cylinders and that's where your coolant is going, but I think it's unlikely.

 

Yeah, that is why I said the oil is its normal darker color. Coolant in the oil would make it milky. I think. Heck, I dunno, its a real PITA trying to track down though.

 

Coolant in the oil, would usually make it milky, but if it's leaking into the cylinders, it could be going out the tail pipe without you ever knowing.

 

watch for more-than-usual steam out the exhaust on cold start. It may also seem rough on initial start, then smooth out as the water blows out. Unfortunately it can be hard to judge whats normal, but something to keep an eye on.

One thing you can count on with leaks, eventually they will get bad enough to become obvious.

 

Going by the amount of steam you see at the exhaust is just more guesswork.

If the UV dye doesn't tell you anything, then the next step is a quick an easy compression test. The next step after that is a more involved compression leak down test. See:

http://www.lcengineering.com/LCTechPages/gentech47.html

https://mobiloil.com/en/article/car-...-leakdown-test

See pages 113-3 to 113-5 of the Bentley manual for specifics. The Cooper S should have compression of 131-196 psi with a maximum 7 psi difference between cylinders. You can follow that with a wet test to seal the rings and see if that changes your readings. Bentley says then you can do a leak down test if that doesn't give you the answer, but doesn't go into detail.

I would probably go straight to a leak down test rather than spend all that time on each of the above tests. Go straight to the answer instead of following bread crumbs. But if you don't have the money to buy an air compressor and leak down tester, then the cheaper UV dye, and a cheaper compression tester, might be worth while to try first.

...AAAAAAAnd, maybe back up and ask if your Cooper S has all the exhaust heat shields it's supposed to have. According to Detroit Tuned...

http://www.detroittuned.com/mini-exhaust-heat-shield/

If your S is missing the heat shield, then presumably it could lose coolant the same way they're saying a Cooper could.

 

Hey Dennis, I just purchased an aluminum expansion tank to replace the leaking at the seams plastic unit. I do have an existing heat shield, will I now have to worry that my metal tank will heat the coolant and exaggerate my coolant loss through evaporation?

 

My R50 never had that coolant evaporation problem; I'm only going by what Detroit Tuned says in that link above. I just thought it sounded like a plausible theory for where the coolant is disappearing to with no sign of a leak. Those guys don't say anything about metal tanks making a difference, so I guess it's fine.

My white plastic aftermarket brand overflow tank was $30 and it doesn't leak. So if you are adding coolant you could try one and see what happens.

 

This is the before picture of the plastic tank



After pic of the new aluminum tank, hopefully this will resolve my slow leak.. More time spent getting those thumb screws in and tightening than removing and putting in the new tank..