Have an overheating problem I have not been able to nail down. We hit an armadillo about a month ago and car started overheating the next day. Had it towed to a very reputable garage who works only on European cars. We do not have a local Mini dealer within 100 miles. Our insurance covered the repairs which included a new radiator, new radiator support, new condenser, etc...flushed/drained/new coolant/pressure tested...all was good. Drove it for about a week and it started over heating in slow traffic. The fan comes on and it starts dropping to normal...figured OK...it's probably the thermostat...ordered a new thermostat and replaced it (third time I've done this on the car..first time in more than 3 years so I figured that had to be the problem. Took it out for a test drive and after about 30 minutes...the overheating returned. No signs of leaks...no oil in the coolant and no coolant in the oil...

Any ideas?

 

Tried bleeding the lines after the car sat for a week. Followed the directions in the Bently manual to refill the system. Cracked the bleed valve until coolant ran freely. Refilled the system, started the engine and had the heater set to high with the fan set to low. After the lines quit burping air I put the radiator cap back on the thermostat housing and went for a ride...same as last time...ran cool until I turned into my drive and the temp started to go up. Scratching my head on this one.

 

Did you replace the thermostat housing and gasket?

 

Yes...replaced the thermostat housing and gasket...that was the first thing I thought would be wrong...figured that would fix it with no problems.

 

Was talking the problem through with a friend and got to thinking if it's just the fan getting old. I've got 160K on the old girl and have never had to change the fan. Thoughts?

Has anyone had a similar problem with a Gen 1 Mini and found the problem to be the fan?

 

If your fan is operating in two modes,(High/Low Speed) I don't think that;s the problem. I had an R50 that overheated. I changed the thermostat and housing and put new fluid in. These cars are VERY temperamental when it comes to having the system bled properly and the correct amount of fluid in the reservoir. Don't be temped to fill the recovery tank to the top. After you are certain the system is bled properly, there are tons of posts here and on youtube on how to bleed the system, make sure you only fill the recovery tank to the line where it says full. You can have the system pressure tested; also, get a block tester with the fluid for about $35. You put the fluid in the tube, push the tube into the top of your recovery tank, let the car get to operating temperature and hope that it does not change colors, if it does, that will indicate you have a bad head gasket. Exhaust gases are escaping into your cooling system causing the excessive pressure. The other option is a bad water pump. Hopefully it just needs to be bled properly. That's all I got as far as troubleshooting your problem.May the Force be with you...

 

That's good advice for sure. I've been playing around with bleeding the system to make sure I had it level. The shop did not install the blue European coolant which was surprising since they only work on European cars so I've been tempted to drain the system completely and put in the blue coolant. Not sure if it really makes a difference but I'm a bit OCD about some things. I changed out the bleed valves a few years ago from the OEM plastic valves because they almost always get messed up and don't want to open...then the plastic slots get damaged...just a mess. I've got metal valves on both the bleed points. I have followed the guidance in the Bentley manual for refilling the coolant and have been patient. Will give it a few more rounds...there's about 1/2" too much coolant right now in the recovery tank so I'll have to see about dropping that a bit. I don't seem to be losing any coolant, no oil in the coolant and no coolant in the oil from what I can tell.

 

You say you are not losing any fluids, when these cars overheat you hear gurgling and grumbling coming from under the hood. Since the R50 does not have a pressurized recovery tank, coolant usually comes gushing out. I'm not sure where the coolant temp sensor is located, is it possible your car is not actually overheating and that Armadillo may have caused some damage to a sensor? When the car overheats is the fan in high speed mode?
I know from experience on my R50, when I overheated and lost a significant amount of coolant, my fan didn't even come on. Fan did come on once the coolant was filled to a certain level.

 

I thought about the coolant temp sensor and may change it. I did change it the last time I changed the thermostat but did not change it this time. It's just to the rear of the thermostat...pretty easy to replace. I did hear some gurgling the last time but nothing major...and definitely nothing overflowing. The fan does click on high speed when it overheats...and the temp drops back down pretty quick...it's just very unsettling to see it keep seesawing back and forth.

 

Just started it up again to look at a few things. Had the heater on high heat...low fan...no air in the lines from what I can tell but realized the cooling fan was not running. Turned on the AC and the fan came on at high speed but never went down to low speed. This may be part of the problem. Will go through the threads on the fan...I know there's ton's of information.

 

Well...did a warm engine compression test. According to the Bentley manual the cylinders should be 167 - 247 psi...only got 120 psi pretty consistently across all four cylinders. The pistons looked pretty clean with minimal carbon buildup on an engine with 165K (oh and a CVT transmission).


Cylinder 1

Cylinder 2

Cylinder 3

Cylinder 4

 

I would try doing a second compression test using a different gauge before jumping to any conclusions. My 409,000 mile Nissan truck has better compression than that (with the same gauge!) and burns a quart every 700-1000 miles. (one owner, never overhauled) Go to O Riley, Autozone, etc. and borrow one from them to compare it. Also, make sure the throttle blade is wide open when performing the test.

As far as the overheating goes, I didn't see you mention anything about the circumstances under which it occurs. Is it idling in traffic or is the car moving? If so, at what speed? Also, was your A/C condenser damaged in the armadillo accident and not replaced? Is it missing a chunk of fan shroud that the insurance didn't want to shell out for? Do you have the undertray present?

 

I'll have to do that. I used this tester on my Nissan two years ago so it's really only been used once before and kept in the box.

The overheating happens after 30+ minutes of driving with the AC on.... I've driven it into town the last two days without it overheating but the trip was less than 30 minutes. I'll double check but the insurance covered a good bit of work...the replaced the radiator plastic tank A/C Condenser, Front Pan/Radiator support, radiator support,

What is the throttle blade?

I'll also do a leak down test for good measure.