The "water pump venturi" theory, if it's even worth being called a theory, is one of the dumbest ideas I've ever heard. It's not that difficult to bleed a mini cooling system. I frequently do it without a vacuum bleeder or using more than one bleed screw.

The highest possibility is that the head gasket is opening up at hot temperatures. Combustion pressure will then enter the cooling system and create new air pockets. I've had a few cars witht this same issue, replacing the head gasket took care of it.

Have your mechanic do a block test. To put it simply its a test that checks for exhaust gasses in the cooling system. It's a quick, easy test and leaves you with only three possibilities; head, head gasket, or block. Gasket being by far most likely.

 

hoping2keepit, I came here to post a pitty-me thread but now I can't bring myself to do it because you covered the first page with overheating threads! lol j/p

Yeah so my car overheated twice, both times in a drivethrough when I had the climate control on auto so it was doing it's own thing with the AC. Couldn't get it to do it again when I wanted to see what was going on so it just kind of sat in the back of my mind...

Today I went through a drivethrough then pulled off to the side to eat before getting on the highway, again with car idling and AC on. While eating I started hearing a creaking noice kinda like when your brakes slip as you let off the pedal, so I go to roll my car forward a couple feet so that it was level and smoke/steam starts billowing out of my hood. I first flipped the heat on, but then figured it was beyond that and shut the car off. An underhood inspection showed that the car had sprayed out about 1/2 gallon of coolant radiating from the expansion tank cap. So my car is now sitting at a McD's parking lot, all alone in the dark while I wait for my fiance to come home and drive me to my car

I've had every bad thought running through my head of blown head gaskets, warped heads, destroyed cylinder walls from overheating, etc. Am I the only one who is surprised there isn't some sort of ding to say hey stupid your engine is cooking! While I'm choking down my crappy cheeseburger I'm not watching my coolant gauge. /rant

Shortly afterwards I turned the ignition switch to "On" to see if the coolant fan would come on and it didn't...

 

All I can think right now is that your fan is not working always and when it should.

Have they checked the relay for the fan. They are noted for failure and causing issues like this..

 

Thanks -- the oil looks great, not milky at all, but that's certainly next on the list.

The good news for you: there's no shortage of threads elsewhere here on fan issues. That's not my problem, though -- the fan's working fine. I'd also venture to say that I don't have to worry about having a 1/2 gallon of coolant spraying out, since the air lock would probably stop the flow long before then.

 

Well I have some mixed news, I went and picked up the mini a bit ago, armed with a flashlight, a funnel, a screwdriver, and some coolant. Didn't appear to be any air in the lines, so I topped it of and drove it home. Still smoked a lot because of the old coolant evaporating. When I got home I checked the fuse box first. A blown fuse! Great could it be that simple?!? Wait, no... fuses blow for a reason. I then poked at the fan to see if it was seized, only to find that it was crooked after I prodded at it. Turns out the cooling fan was complete seperated from the motor, and just sitting there behind the fan shroud, hense why the fuse blew. Well I looked, and I didn't find any threads for my exact problem lol.

But anyways not trying to hijack your thread, but the 9 steps that another poster described for flushing, filling, and bleeding your lines should solve the problem if that was it, bleeding the lines are a pretty straight forward ordeal so not somehting you should have to do more than once. When is it overheating? Only when parked or when your doing highway driving? If air is moving through the radiator when it overheats (while you're driving) then it's either the thermostat, air in the lines, or a kinked hose. I found an acorn wedged in a thermostat once. If it only overheats when sitting then it's something to do with the fan.

 

It's definitely NOT the fan for me; the fan works fine. (Hearing it from across the parking lot was the first indicator something was amiss...)

As for bleeding the system, oxybluecoop posted a great DIY how-to on another thread: https://www.northamericanmotoring.co...39-post12.html

(It's been fine since Saturday, but I'm just waiting...)

 

+1 - If your cooling system works when driving it cant be the pump and cant be the thermostat, and cant be a kinked hose......

I still say it's electrical....The fan relay has always been an issue with these cars and symptoms are pointing that direction.....time will tell.

 

not trying to be a **** but the cooling fan on the mini has 2 speeds, are they both working?

the first stage is the one that works most of the time and the one that usually gowes bad - but you will still hear the second stage work.

good luck

 

I have simtums too. mine has been boiling over only when i go up hill or at the auto X.I changed the thermostat 3 times ,overflow tank cap 3 times . bought a new radiator fan ( both speeds work great)took out the waterpump.it seemed fine(held one side and tried to turn the impeler) no slipage and all was clean. changed the hoses,the spark plugs and wires.pressure tested the system,still over heats when it should not .I even blew through the radiator with my mouth. had a little resistance,so i dont know bout that. I have been useing strait water for over a month cause of the boiling over.wonder how fast deposits would form? but still I can't think of what can be wrong. help me, obewone.

 

Haven't heard back from the OP so I guess it's resolved?

pmfranke, deposites form faster than I'd like using tap water, if you must save some money on coolant buy distilled water. It's like <$1 a gallon. As far as your issue I'd say the water pump is most likely. Radiator's usually take a very long time to just go bad, unless they have suffered some sort of unusual damage, most of the time it's visible from the outside.

 

Jury's still out. It's been fine for over a week now, which is definitely a good sign. Interestingly, I noticed the second day the coolant level in the reservoir was much higher (1/4" below top) than where we'd filled it (just below max) -- but the level does go up & down as it heats and cools, and hasn't gotten any higher than it did that first day.

I'm hesitant to officially call it "resolved" since I've thought it was resolved before, only to have the problem resurface after a couple weeks. I've had a week of not hearing the fan or seeing the temp gauge go past the mid-point, though.

 

took the water pump out again no blockage or sliping between the impeller and keyed side. used distilled water. runs great starts perfect just dont accelerate or go up hill and im fine . bugga the water pump is so expensive ,just to try it and hope seems crazy. A friend told me it might be a head gasket but they tested that at the rad shop. really driving me crazy. i guess i should try the power bleed next,caus I have so much extra money to waste on extra water pumps and radiators!!!!NOT

 

My fan came on again after I parked on Thursday; started overheating on my way home yesterday. Hooked a pressure gauge up this morning, and let the engine run. Pressure was pretty stable -- unless we gave the engine gas, at which point it would drop, then jump way back up. Don't think it's major, but just enough for air to build up over time (ca. 2 weeks.)

Looking at part numbers, it looks like the stock gasket has been replaced with a different part that's 1/3 thicker? That seems like a big difference to me, indicating MINI realized the original wasn't up to snuff.

Not looking forward to the cost of repairs, estimated between 800-1000 (depending on whether or not the block has warped from the heat & needs to be milled.)

 

I would venture to say that your block will most likely be ok; it is cast iron after all, not soft aluminum. So the head will warp long before the block does. The results you had with your pressure gauge are the same results that I found the first time I ran into this issue; I'm standing behind my previous prognosis and your latest idea. Do the head gasket, have the head machined and you should be fine. Make sure they take a good look at the exhaust valves when they have it off. I've seen a bunch crack, but mostly just on 02's and early 03's.

pmfranke: I would just about wager my next paycheck that your problem is a head gasket too. You can do all the tests in the world, but if it's not overheating when you're testing it will pass every test. But double check to make sure your fan is working, turn your AC on and let the car get nice and warm, get under the hood and listen for a loud fan noise in front. I'm still going with HEAD GASKET.

 

for a head gasket. Find an independant Mini shop for ANY WORK that is not covered by warranty. You'll be glad you did.

If you're mechanically inclined, you can do it in your garage (or driveway). Hardest part is getting over the fear of the work.

Matt

 

The 800-1k quote actually is from an independent shop. (I can't even imagine what the dealer would charge...)

I actually do have access to a mechanics' "club" of sorts that's not too far away -- something like $6/hour for garage & tool rental, plus folks there will help you out -- which I'm increasingly tempted to try. (Might as well get some practice in before the CVT goes out again, right? ) I don't know if anyone there has any MINI experience or not, though -- plus with young kids, it's hard for me to get away for that long. (The mechanic's estimate was for 7 hours. Is that reasonable for a head gasket?) For the cost difference, though, I just might be able to convince the wife.

 

Danny at Mini Corsa does them much faster. I take a lot longer! I think it depends on how many they've done and how familiar they are with the job. What's the big unknown here is if your head is warped all work will stop at the half way point to fix that.

Matt

 

Yeah, I don't know if the club I could join has the necessary equipment to fix the head. I'll find out this week. [Can't afford the work yet, so it's currently getting re-bled again to buy me another couple weeks of not overheating...]

 

Keep in mind that the Chilton's book says 8.0 hours for an R50 head gasket, 11.2 for R53. 7 hours is a good estimate, as is 800-1000. Say 150 cost for all the parts, another 100 for machining. I wouldn't ever do a head job without machining, especially with an aluminum head. I'd take that price in a heartbeat. Someone who does a lot of mini's is probably around 6-6.5 hours on an R50 for a head, but I doubt that you will find anyone who will charge you less than 7 hours. They do that just to be fair to all of their customers and to cover their own butts.

If anyone has any Chrysler experience at that club you should be ok, it is a Chrysler motor after all. Think neon.

 

well I got it filled with radiator fluid by vacume and it really was running well, but going over the hill to honolulu it over heated again. SO, im going to do the head gasket next . I'm really not looking foward to taking it all apart again ARG.I have been told by some that I should get new head bolts because of stretching caused by my 19% pullie. some said they use the old head bolts but I 'm thinking ARP studs because of the autoXing i do. wondering if someone makes high performance copper head gasket to cure this problem . Just some questions and more questions

 

I think by Comtec (don't know if I remember the name right). The head bolts are "stretch to torque" and are supposed to be one-use, but I know people with TONS of power who re-use them without issue. Stud kits are a cheap add on when all is said and done with the work.

Honestly, it's not a hard job, just takes a while and you've got to go slow and it will all work out well. I did my head something like 60k ago and it's still doing fine. I had a leaking gasket, tried to just torque the head down. and it was fine till I floored it to redline. Dash lit up like a christmas tree! I called that "stress testing" and it failed.

Matt

 

Those bolts that stretch are called "Torque to Yield" bolts. You should never re-use them, they won't hold torque properly after being stretched once and there is even a possibility that they could break. The bolts aren't stretched because of your pulley, they stretch because they are engineered to. The only bolts that you will re-use on a mini are the two small ones by the timing chain on the far passenger side.

Head studs are one of the best upgrades you can make as far as reliability goes, especially if you are running more power than stock. They are stronger and they don't stretch which means they will hold the proper torque longer. Get the studs.

 

Thanks , I ll be paying for the ARP studs upgrade.found them 4 a 100 bucks.found a head gasket kit for 216. I sure hope the head is not cracked I will look for that high performance head gasket too.I found that there are two thickness of gasket also. I hope a thin one wont pump the comp /ratio up to the point of 92 octane gas not working. so much to know ....so few -brains

 

I sincerely doubt that just a thinner gasket and machined head would bring it beyond 92 octane; if it does it won't be anything a little octane booster won't cure.

hoping2keeptit and pmfranke, let us know how your repairs turn out. Good luck

 

Could not find the other company's head gasket but I found a comp head gasket made by Cosworth for 80 bucks wonder how much better or if i really need it given the ARP head studs I will be using?