Hi, Folks. I think I have this figured out, but wanted to confirm since the Mini isn't really "normal" in most areas of function/repair

Car is '08 Mini Hatch, N12 engine, auto tranny. Car has cold weather package. Recently had the radiator replaced by dealer due to leak. This is my first winter with this mini (122K miles on the odo), and I'm trying to figure out how this thing warms up in the winter. Initial symptoms were little to no heat after driving 5 miles when car was in the semi-heated garage, but outside temps were in the teens. I figured it could be one of three things - stuck-open thermostat, air mix door not opening, or (worst case) clogged heater core.

In diagnosing the problem, I found that if I drive the car for 20-25 minutes you start getting decent heat out of the vents/floor, but never really "toasty" like in every other car I've driven. So that eliminated the 2nd and 3rd ideas as I listed above. I theorized it was the t-stat, but without a true coolant gauge it was hard to tell. So after some research I sprung the $69 for an Ultra-Gauge (basic one). It came in on Friday, and I hooked it up and started looking at the coolant temp. I'll have to play with all the other gauge data I have at my fingertips- the Ultra-Gauge is a great tool!

Anyway, tried today. Car outside in mid-30's and clear. After a 5 mile drive the coolant temp only got to 128F. After driving another 10 minutes it got to about 160 - and the heat inside the car was good. Driving home (after about 20 minutes total) the temp finally got past 190, and hit 204 at the max - but you could see it fluctuating up and down slightly in that range. So, for me, this was the evidence that the t-stat was open all the time.

IN researching threads in the forum on t-stat replacement, it doesn't look too bad. But in reading the service manual, it talks about how the t-stat has an electronic control in addition to the manual control. And (of course) the only way to replace the t-stat is to do the whole enclosure with new sensor (etc) to the tune of $97 for a mini OEM unit (local dealer gives 20 percent off parts).

Does the electronic control do anything different than a normal t-stat does? Does the behavior change in watching the temp rise?

thanks much for your help.

andy

 

In highway use if the thermostat was stuck open the coolant temperature would keep dropping as the coolant would be continually flowing through the rad. it would not basically stay up but fluctuate.
I find these mini's warm up slowly.

 

Another possibility, air in the coolant. I would bleed it to see if air comes out..

 

Two thoughts:
1). Are you sure the air was properly bled out of the cooling system post radiator swap?
2). How cold is it in NH these days? Down here in NJ with morning temps in the teens, it usually takes me ~5 minutes before the engine warms up enough to start heating.

Not really - if it was open, the temps likely would have plateaued somewhere well lower.

For what temperature is the t-stat rated to open 95C ?
That would be 203F.
In that case, as soon as the temps reach thereabouts, the t-stat should open and the temps would drop. Then stabilize, then creep back up to 203 until t-state opens wider and drops them again. Repeat as necessary.

Based on your date, it appears the t-stat is working fine.

HTH,
a

 

Thanks to everyone for the feedback. While I tend to agree that my longer run temperature behavior shows the t-stat shows the proper settling point just over 200F, I'm still amazed at how slowly this car warms up. My experience with 4cyl motors has been they warm quickly and you get decent heat faster than with a V6. Thus the reason i started questioning the t-stat. Given that I've now got the Ultra-gauge set up I'll drive it for a couple of weeks and watch the temp pattern and then decide. Given that it's not causing a problem - and that the cost isn't chump-change to have this replaced - I'm not rushing into anything. I may, just for peace of mind, do the replacement myself once the weather warms up. Even in my semi-heated garage, I'd prefer not to work on this unless I'm forced to.

thanks again for your help!
andy

 

+1 Are you sure the air was properly bled out of the cooling system post radiator swap? Bleeder screw at the top of the thermo and you can reach it with a long Phillips screw driver, turn the screw out slow until it bubbles the air/coolant and not all the way out as it might pop off and loose it. Happened to me once

Make sure air is out, sometimes it takes a couple times to bleed the system. When there is air the system does not get real hot, sometimes if low enough you will get a Thermostat error. For the thermostat leak, you will see small drip at first under the thermostat on the back side and drips down on the transmission. ( You might not see it at first).

Check both those first.

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



Good luck, thats all the info I have.