Forum Thread

(Intermittent) coolant leak?

Dr. J 25,042 3,353 August 1, 2016 at 05:26 AM
So I get back from ~ 4 weeks away from home on Saturday and take my car for a spin into town on Sunday. A quick ride to town and back with no issues. Then later in the day I had to drive to the IL's about 30 min away. After a minute on the highway the temp light goes on in my car - first yellow, then red. So I pull over at an exit to check and sure enough there is ZERO liquid in the tank. I have a ScangaugeII which is always connected to the car so I can see the realtime temp.

I know from previous experience that the car (MINI R55 2008) runs hot, about 218-220, but it was spiking to 240-250 (even saw a 260 briefly). So I limped home, put about ~ 1 gal of diluted AF in it, then started it up and revved to get the tstat open, then topped it off as the system filled. I then sat in the garage and revved it to 3k (about where it runs on the highway) for about 10 mins and the temp maxed at 218 as predicted. I did this twice. I would have taken it out on the road but I had DD @ home and didn't want to strand her out with me.

That was yesterday (Sun) PM; I let the car sit in the same place overnight and the liquid level in the tank hasn't changed. I'll probably take the car out tonight once I get home from work (borrowed a car from the FIL).

So I was talking with the FIL, who took care of our house while we've been gone and he said that he noticed a leak, but couldn't give specifics other than that it seemed to get worse when the car was running (he only turned it on to move it to mow the lawn) He forgot to tell me about it when I got back.

So - car is fine for the longest time, sits for 25 days where all the coolant drains out, so I fill it back up and AFAIK there is no more leak. FWIW I did have the water pump changed out a few years ago (when it failed it was pretty obvious, sudden big puddle on the ground).

So I am soliciting thoughts on what went wrong - could the car just sitting around for 4 weeks (more or less) be the cause here? FWIW I've never really had issues with coolant, I don't recall much if I've ever had to top it off.

I have a digital borescope I'll try and poke around later today to see if there are any obvious leaks, but other than that I might just start driving it and monitor.

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So you limped home with no coolant? Yikes!

Check the obvious and easiest first, Hoses for cracks, you could use some dye and a UV light. Check the radiator and overflow caps too. Bleed the system for air too.

You have the benefit of it being a mini and a ton of enthusiasts and forums around on line. I think I would ask there too.
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Quote from LiquidRetro View Post :
So you limped home with no coolant? Yikes!

Check the obvious and easiest first, Hoses for cracks, you could use some dye and a UV light. Check the radiator and overflow caps too. Bleed the system for air too.

You have the benefit of it being a mini and a ton of enthusiasts and forums around on line. I think I would ask there too.

Yeah. It was hairy - fortunate for the SGII otherwise all I have is the idiot light. I'd go slow then put it in N (stick) when I could to cool down the engine. The last leg is a hill up to my house so I left the car at the bottom and walked back some coolant. It was all I could do at the time unfortunately.

I did do a check by eye for obvious places - ends of hoses, etc, but didn't see anything. Of course the coolant has been gone from the system for a few weeks now, and everything is dried. And, as I said, when I got the system filled up again it hasn't leaked.

Last night I left a piece of cardboard under the car and there was some evidence of some kind of liquid leak (wet spot on the cardboard) but the reservoir level did not change, so it's likely the liquid was either residual on the support members.

The next thing is to take the car on the road, I think - short in and out trip to get it to temp and working then back to the garage, and monitor the coolant level.

There is no cap on top of the radiator (well, the radiator is well hidden so if there's a cap, you can't access it) and getting access to the radiator is a PITA so it's not like I can just inspect for leaks easily. I do have a digital borescope as I mentioned so that might make it a bit easier.

Just wondering if it's common for older cars (e.g. older hoses, radiator, etc) to have leaks like this when they are left for periods of time.
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Quote from Dr. J View Post :
Yeah. It was hairy - fortunate for the SGII otherwise all I have is the idiot light. I'd go slow then put it in N (stick) when I could to cool down the engine. The last leg is a hill up to my house so I left the car at the bottom and walked back some coolant. It was all I could do at the time unfortunately.

I did do a check by eye for obvious places - ends of hoses, etc, but didn't see anything. Of course the coolant has been gone from the system for a few weeks now, and everything is dried. And, as I said, when I got the system filled up again it hasn't leaked.

Last night I left a piece of cardboard under the car and there was some evidence of some kind of liquid leak (wet spot on the cardboard) but the reservoir level did not change, so it's likely the liquid was either residual on the support members.

The next thing is to take the car on the road, I think - short in and out trip to get it to temp and working then back to the garage, and monitor the coolant level.

There is no cap on top of the radiator (well, the radiator is well hidden so if there's a cap, you can't access it) and getting access to the radiator is a PITA so it's not like I can just inspect for leaks easily. I do have a digital borescope as I mentioned so that might make it a bit easier.

Just wondering if it's common for older cars (e.g. older hoses, radiator, etc) to have leaks like this when they are left for periods of time.
Seems to be a common problem with this make/model. http://www.northamericanmotoring....-leak.html

http://www.pelicanparts.com/techa...cement.htm
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Last edited by LiquidRetro August 1, 2016 at 10:21 AM
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Quote from LiquidRetro View Post :
Seems to be a common problem with this make/model. http://www.northamericanmotoring....-leak.html

http://www.pelicanparts.com/techa...cement.htm

I don't think it's that:

- I have an R55 (clubman), 2008 - not within the "official" problem tanks
- I didn't see leaking from the tank itself
- I know the system can hold at least some pressure - while I was revving to 3k I did take the top of the tank off a few times to top off the coolant ( tstat opens, etc.... I am sure the system wasn't completely out of coolant but you can't fill the whole thing while it's cold either) and I did meet pressure several times

So that's the other bit of info.... the system does pressurize, so if there's a leak it can't be a bad one.

Wondering if this is one of these things that I'll have to eventually chalk up to.... hoses or whatever sealing when they're used regularly.

Oh yeah and I may have had some system components replaced. I've been in 2 accidents with this car and (especially the first) one of them had front end damage where there's a very good chance the radiator was replaced.
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Seems simple but have you tried replacing the coolant cap? It is pressure rated and when the cap is defective/broken, the car will overheat in a hurry. The system MUST be pressurized to not overheat. I'd say start it, fill it, let it sit there and get nice and hot. Could take 1/2 hour. Watch the cap and see if it let's loose. Also are you smelling anti-freeze? Could be a heater core too.
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Quote from dealgate View Post :
Seems simple but have you tried replacing the coolant cap? It is pressure rated and when the cap is defective/broken, the car will overheat in a hurry. The system MUST be pressurized to not overheat. I'd say start it, fill it, let it sit there and get nice and hot. Could take 1/2 hour. Watch the cap and see if it let's loose. Also are you smelling anti-freeze? Could be a heater core too.

No AF smell. Car uses Zerex FWIW.

So far I've eliminated WP and tstat; also the system does pressurize and there are no visible leaks. Right now if I didn't know about the craziness that was Sunday, I'd say the car is 100%, because it will get to and stay at temp without issue. As I said I haven't taken it on the road yet, which I'll hopefully get to do tonight.

I really don't want to get into "replace parts" mode, otherwise the radiator and all hoses would be replaced. It's not expensive (radiator is like $60 @ RA) but a huge PITA.

Not something I want to get back from a month away overseas to have to deal with.
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The reservoir level not going down when the engine cools can mean:
  1. The radiator cap is bad.
  2. The radiator cap is the wrong type. Regular caps open up when the pressure gets too high, allowing excessive coolant to escape, but reservoir tanks you need a cap that opens up as usual when the radiator pressure is high, to let coolant into the reservoir tank, but when the engine cools down and a vacuum forms in the radiator, the cap has to open up to let coolant in the reservoir get sucked back in.
  3. A break in the hose betwen the radiator and reservoir or loose fit where the hose attaches at each end, allowing air to get sucked into the radiator.
  4. The hose fitting on the reservoir or radiator is cracked, allowing air to get sucked into the radiator.
  5. A blown head gasket lets air get sucked into the radiator when the engine cools. But this should also make the exhaust blow out white water vapor, maybe huge clouds of it.

If your boroscope can fit through spark plug holes, remove the plugs and check each piston because a piston that's a lot cleaner than the others indicates water got in and cleaned the cylinder.
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Well got home, revved to 3k and held temp for about 10 minutes.

Then took it on a 20 minute drive on the highway - maxed at 222 maybe a couple times, most of the time between 215-220 and some usual dips into the higher 100's - all as usual.

Got back and the tank level was in the exact same place (I marked it last night).

So next step is to take it to work and monitor. Frankly that's all I can do until the problem recurs and I can check for where a leak is coming from. I also left some cardboard under it overnight again if there is leakage.
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Quote from larrymoencurly View Post :
The reservoir level not going down when the engine cools can mean:
  1. The radiator cap is bad.
  2. The radiator cap is the wrong type. Regular caps open up when the pressure gets too high, allowing excessive coolant to escape, but reservoir tanks you need a cap that opens up as usual when the radiator pressure is high, to let coolant into the reservoir tank, but when the engine cools down and a vacuum forms in the radiator, the cap has to open up to let coolant in the reservoir get sucked back in.
  3. A break in the hose betwen the radiator and reservoir or loose fit where the hose attaches at each end, allowing air to get sucked into the radiator.
  4. The hose fitting on the reservoir or radiator is cracked, allowing air to get sucked into the radiator.
  5. A blown head gasket lets air get sucked into the radiator when the engine cools. But this should also make the exhaust blow out white water vapor, maybe huge clouds of it.

If your boroscope can fit through spark plug holes, remove the plugs and check each piston because a piston that's a lot cleaner than the others indicates water got in and cleaned the cylinder.
I had a car once that blew a gasket and coolant over a certain level would get into the oil almost immediately. White smoke, frothy oil, etc, classic case. You could literally fill it to the recommended level and within a few minutes driving, it would be back down again. I don't see any of that here.

What I've seen is -

- car runs fine no issues
- car sits for a few weeks, FIL says that he sees coolant leak especially when car is running, but this is just anecdotal
- car runs fine for short trip then overtemps after a couple mins on the highway - reservoir is completely empty (surge tank) - radiator is probably down at least 1/2 gal as well (I don't know what the system capacity is)
- fill system back up such that it is bled and surge tank is between min and max levels
- car runs fine no issues several times including 20 minute trip on the highway

The system does hold pressure. No observed leaks. No exhaust issues. No impact on engine performance (AFAIK).

It's like there was a leak and now it's fixed itself. If any of your above ideas were true, I'd see it somewhere - especially in coolant level.
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Update - I've been driving the car the past couple of days which included 3 separate (cool-hot-cool) ~ 35 mile mixed highway trips (to/from work) and a couple smaller trips (lunch). Coolant level hasn't budged (on a net basis, meaning cool-to-cool the level is the same) and the temp has behaved as I'd expect it (SGII).

So.... I still have IL's car and will give it back to them this weekend. Not sure what to attribute the sudden loss of coolant to.
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Is it possible the system simply needed to be "burped"?
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Quote from dealgate View Post :
Is it possible the system simply needed to be "burped"?
not when it's on the ground
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Quote from dealgate View Post :
Is it possible the system simply needed to be "burped"?

you mean purged?

Still running fine BTW. Unfortunately the FIL didn't investigate the leak he saw otherwise I might have had a clue as to where it came from. Now the system is self contained for nearly a week after several cold/hot/cold cycles.
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Quote from Dr. J View Post :
you mean purged?

Still running fine BTW. Unfortunately the FIL didn't investigate the leak he saw otherwise I might have had a clue as to where it came from. Now the system is self contained for nearly a week after several cold/hot/cold cycles.
My DeVille was an absolute beootch to fill. It took sometimes days (literally). With the DeVille it is called "burping" because that is what it eventually does. You can watch the overflow almost come out, in fact some does spill out, then it "burps" - sputters all over - and you can put in an extra almost gallon. TOTAL PITA! Of course if you have a visual leak, that is a different story. But did YOU ever see a leak? So many people think the A/C condensation is a coolant leak. Is your FIL a car-guy?
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