i'm a new owner of a 2005 mini cooper s convertible. bought it a few months ago, with no issues, until yesterday. overheated for unknown reason. today, refilled the reservoir, and ran it up to operating temperature. hot steaming coolant is now "oozing" from under coolant reservoir cap. so, bad cap seal or bad thermostat that wont open? any ideas? thanks in advance.

 

Make sure you are bleeding all the air out of the system when you add coolant. Also make sure your expansion tank is not cracked, it's a known issue. I replaced my expansion tank with a canton racing tank from summit racing. Jan at RMW has a similar replacement tank now too.

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i read about the cracked plastic tanks, and i dont see any leaks around the tank, only from under the cap. thanks for the reply.

 

I figured it would not be that obvious. What coolant are you using, when was it last replaced and make double sure you bleed any air out of the system.

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zerex g-05 50/50 mix. i'm assuming ( i know what they say about "assume-ing") that it was changed prior to the sale to me. i bought it from the BMW dealership, and it was certified pre owned.

 

That's the right stuff but I would not assume the coolant had been changed just because it was certified. By the way, when did you buy it? I am not familiar with the MINI certified pr owned or CPO program but would not think an 05 would be eligible for CPO designation.

I have not changed a thermostat yet but have changed the coolant and tank. I have also not overheated either. I don't know how easy it is but I can't imagine it's too difficult. My recommendation would be do all the cheap stuff first ie coolant flush and thermostat. Ther are several good posts about how to change the coolant on NAM. good luck!

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Top off, perform bleeding procedures and put a NEW cap on.

If your tank has signs of leak at the seems, and it should by now....get a whole new tank which comes with new cap. Then perf. bleeding procedures.

Also check area around thermostat for signs of prolonged seepage. Can only get a new gasket with a new OEM thermostat.

 

You can purchase just the gasket here: http://www.rockauto.com/catalog/moreinfo.php?pk=4006716. But if you go to the effort and or expense to change the gasket, you might as well change out the thermostat and the housing at the same time. That's what I did for the peace of mind. Total parts cost was around $80 plus or minus. Good luck.

 

That isn't the updated superseded gasket from MINI though and since as you stated in most cases they tend to leak at about time when it would be a good idea to do the thermostat as well, seems like a better idea to me to do both as the same time. I personally prefer not to cover same ground twice in cases like this.

Also, could be this one from rock is only as good as the one being taken out...just that I have found in most cases, especially head gaskets, the aftermarket ones blow.

 

hey buzzsaw, i see that the link is for the thermostat gasket. i dont see a leak from under the car, or around the thermostat.

the only leak i see for now is from the coolant resevior cap. my thought is that either (a) the cap seal is bad, and is leaking from high pressure/heat or (b) the thermostat is bad, not opening under normal driving temperature, and thus forcing coolant to back up into the resevior and out from under the cap.

but i'm not a mechanic, nor do i play one on tv. with that being said, i could be wrong all together.

 

hey swimbaxter, i bought my R52 last august. i think it was a CPO because of its low mileage (92,000).

 

PS
the "COOLANT TANK" doubles as the expansion tank....
Filling it more than about HALF WAY...look at the markings on the side...will result in venting excess coolant from the top, and will hasten the seam failing where the two halfs are glued together....

 

Best way imo to get a new cap, imo, is to buy a new tank(should come with a cap)...you will need it eventually...so just swap them both out ....just need to change one clamp and a couple nuts, then bleed.

 

so i may have just screwed myself. i called this so-called "warranty" company that i bought into when i bought the car. i explained the overheating situation, and asked if it was covered. the rep went on to tell me that only the thermostat was covered, but not the housing or coolant resevior. she then advised me not to drive the car, and have it towed to a licensed repair facility. when she told me there was a $500 deductible, i told her that i could replace the thermostat for ALOT less than that, she went on to say that i was "not allowed" to fix it myself, and that if i did, the contract could be voided. AUGH!!!!!

 

When did you purchase this car/warranty? You can get a refund on the warranty prorated unless it's the first 30 days in which it is 100% refundable.

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i bought the car august of last year.

 

When we changed the thermostat on my 06 mini it cost us 350.00. It was having the same problems it over heated and went to limp mode (?) And wouldn't go past 30 miles. When we took it to the shop they tried to blame it on a blown head gasket and the thermostat. So we decided to change the thermostat and see how it drove and I havent had a problem ever since. I thought they were trying to rip us off lol but damn 500.00

 

Did the Canton tank come with a cap? or do you reuse the cap on the stock tank?

 

The cap is not included but they sell them too.

 

i was unsure if the issue was the expansion tank or the thermostat not opening. i changed the expansion tank with an OEM unit, and it fixed the problem. i may have even got away with just changing the cap of my old expansion tank, and see if it was just the seal under the cap, but i went ahead and changed it all out to be on the safe side. i was only able to find 1 bleeder valve, which was directly in the front of the car. i bled the coolant a few times, and i havent encountered any issues, its been 2 weeks now.

now my A/C is acting up, fix one thing, and break another. FML

 

Well.. good to hear part of it is fixed....the other coolant bleed line is kinda hidden near the thermostat.
This early in the year....I would lean towards needing a refill of r134a ...but the mini uses a tiny amount total...about 16 oz from empty...so it is easy to overfill with oil/r134a.
IF you live in an hot area (some do special deals...like a $40 top off) ...letting a pro do it with a full set of gauges might make sense IMO. A diy kit for $40 or so is OK...just resist the urge to add extra...too much is not good.

 

I replaced my Tstat and housing myself , bought the parts from Autohaus for less than $70. My OEM tank was leaking from the center seam also and replaced it with Canton much better price than forge.

 

sooooo lets say hypothetical, someone i know, that has a friend, who's brother's exgirlfriend's cousin purchased one of those DIY R134a kits, and put too much in, what would happen? i'm not saying i did that or anything like it of course.....

 

Depend on the kit...
But too much can cause compressor wear...higher than normal psi ...can lewd to a physical failure ....
Now there is REAL performance issues from it too...
Too much oil results in reduced cooling capicity....it will do fine in moderate temps, but fail too cool in hot temps...(many DIY cans have instructions to shake can as you add gas to send a mix of oil and 134a) ...too much 134a...well about the same...inadequate cooling...remember expanding gas causes the cooling...that is why pro kits have a LOW AND HIGH side psi gauge...DIY kits have just the low and you infer/guess the other psi by seeing the psi drop when the compressor is cycling.....
Also of note...most DIY kits have a "genaric or universal PAG oil...not the same as is actually needed....