I swear. My "daily driven project car" is always full of surprises during repairs. Last year when I replaced the valve cover gasket, I noticed one of my cam lobes wearing excessively. Today, I replaced all the plastic tees in the cooling system and all the coolant hoses for an R53 that FCP Euro had only to find there are many other short hoses (to the oil cooler, down to the pipes behind the engine, between the tees, etc...) that I did not know about nor have to on hand to replace today. FWIW, this job really sucked - hose clamps that my hose clamp pliers could not grab and very little room to mess with those clamps and pull hoses off of pipes and tees.

The reason for this repair is my car overheated on the freeway offramp after driving home from work that day. I should say I noticed it was overheating on the off ramp and then steam bellowing from the bonnet when I got stopped because I honestly had not noticed then temperature gauge until the off ramp. When I looked under the bonnet, I was horrified to find one of the plastic tees had broken completely off, leaving my cooling system wide open for the water pump to pump all the coolant out of the engine. This was about 1 mile from my house, so I left it on a side street to cool off for 3 hours after which time I was able to drive it home and park in my driveway with no running problem.

I had my car towed to my dealer and completed the repairs today. I vacuum filled the cooling system and pressure tested it once it was full to make sure my cooling system is sealed tight, after which I started my car and let it idle in the shop for about 20 minutes while I put the wheels back on, set tire pressure and washed up for the road test. The temperature gauge remained right in the middle like normal and the engine was idling smooth, so I left the shop for a somewhat long road test to get the engine nice and hot because I'm not sure the overheat didn't warp the head. I had not gone 1/4 mile before I noticed the engine temperature climbing and before I could turn out of the auto mall loop, the gauge read full hot. I cranked the heat on full blast and turned around to return to the shop, the engine still running fine.

I open the bonnet and found the expansion tank wet with coolant, so I grabbed my thermal imager so I could look at the cooling system for anything unusual. I was quite surprised to see my radiator appears to have a large restriction in it. I installed this radiator in January 2021 when I replaced my supercharger. This radiator replaced my 18 year old, original radiator that came with the car (not leaking), so this was really unexpected. Luckily, this radiator was purchased from FCP Euro, so I can make a warranty claim on it but I'm really not looking forward to pulling the radiator core support again, which will be the 4th time since January 2021 that I've done it.

This is a picture from my phone of the image from my thermal imager:

 

Damn! - I read a lot of threads here on NAM - Some of these problems I read scare the heck out of me. I have a Bentley. However, This doesn't look like a problem I could handle myself = deciphering, labor, having the proper space and tools.
Relenting to the dealer for repairs is something I hope to avoid. You, having that Thermal Imager is a tool I would never have even thought of.
I don't envy the problem you are facing - I do envy your experience and ability to troubleshoot and the fortitude to do most of the work yourself! = I'm impressed!

 

A faulty thermostat might also cause this, and is much more likely than a 1 y/o plugged radiator.

 

That is what one of the other techs in shop suggested when I pulled back in and that is what caused me to grab my thermal imager. The thing is I replaced the thermostat housing (new thermostat was in it) at the same time as I replaced the radiator and water pump. In the image, you can see the upper radiator hose running behind the radiator support and it is hot.

Though I have already ordered a replacement radiator and I must be a gluten for punishment because I ordered an all aluminum radiator, which I understand have a tendency to leak every couple of years or so but I am not closing the book on the thermostat yet. Once I am ready to start the car next Saturday, I'll have the thermal imager ready to watch, among other things, when/if the thermostat opens.

The other question not answered yet is the coolant on the expansion tank during the overheat. Being that I pressure tested the coolng system to 100 kPa (15 psi) prior to starting the engine, that leaves either the cap is faulty or pressure in the cooling system during the overheat exceeded the cap blowoff pressure. On that note, does anyone know what the blow off pressure is? I am guessing 100 kPa but it could be as high as 145 kPa (~20 psi). I only test at 100 kPa because I figure that is sufficient pressure to blow off any hoses I may have left loose.

@Here2Go - Thank you for the encouraging words! I am a professional technician (at a Ford dealer now, Volvo before that) and a tool junkie. Overall, I very much enjoy what I do but there are some jobs I have to grind through. As I was replacing these hoses and tees on my R53 yesterday it was one of those times I was just grinding. I marvel the guys who do this work on their garage floor with a fraction of the tools I have.

 

My t broke also, some time ago. Seems like a weak point.

the res tank will split under pressure. It’s meant to “relieve” the presure I’m told. Put a fresh one in there

 

F.Y.I. Your coolant is going to run very close to boiling (100C) and that's normal for a MINI particularly if you're driving in traffic with frequent stop/starts. Your coolant tank overflow is most likely a faulty cap. You didn't mention replacing the water pump so I'm assuming you've discounted that for some reason. Since you're an auto tech this may be a silly point, but it's easy to install the thermostat backwards and that would also cause a heating issue.

 

Some years ago, I was a serious hobbyist woodworker. My philosophy was that every project was an excuse to buy at least one tool. I've carried that over into my car-tinkering. What I marvel at is the expertise that many here have. I learn something just about every time I visit NAM. That thermal imaging tool is pretty sweet too.

David (who works on the garage floor but has a serious set of jack stands)

 

How long have you had this car?? I ran into a similar problem with a car a few years back where someone put radiator stop leak in it instead of replacing a leaking radiator. I replaced the radiator and it plugged the new radiator within a couple months. When winter came, I found out it had plugged the heater core also. The stop leak crap apparently hides in all sort of nooks and crannies in the cooling system and will plug every small hole it comes in contact with. I didn't know what it was at first but showed a senior tech what the heater core was full of and he said it was stop leak.

On another note, I don't think its necessary to pull your radiator support to replace the radiator. I didn't anyway. And I've replaced the radiator on my Mini twice due to an animal going through my brand new radiator within a week or two of installing it.

EDIT: I have an R50 not an R53. Maybe the process of replacing the radiator on an S is different?

 

I went back and read your post again and it sounds like you've had the car awhile so scratch the stop leak comment. I don't think 143 F is very hot for any car let alone a Mini. Did you take any readings of the head or t-stat housing area? It sound like a plugged/bad t-stat or failed water pump but you replaced both of those.... My car will boil brand new fluid with the fan running on high if the pressure cap isn't on (R50 cooling system is completely different just fyi), but with a Fluke IR thermometer most of my radiator will read over 200 degrees F.

I had another thought though, your water pump is driven by your supercharger. Ever had the back plate off? See video below.

 

Yes, I have owned the car since new and have done all the work on it since warranty expired.

In January 2020, I installed a Detroit Tuned supercharger due to the infamous "box of rocks" noise from the supercharger (158k miles on that supercharger - without any service). That supercharger, I did take the back plate off and found no oil but metal dust and very sharp, worn teeth on the 2 gears. I replaced that supercharger with a unit from Detroit Tuned and at that time, I installed a new water pump, thermostat housing (small leak from it) and radiator (because I was there and it was the original radiator), among some other parts but those were all the cooling system related parts I replaced. I vacuum filled the cooling system with 50/50 Mini coolant and distilled water.

2700 miles after that (in July 2020), that rebuilt supercharger began making the same noise as my original. Since that supercharger was under warranty from Detroit Tuned, I could not open that one for diagnosis but they promptly sent a replacement and it has been fine since I installed it last summer.

The cooling system has been perfect until I noticed a small leak from one of the plastic tees near the back of the cylinder head. About a week after I noticed the leak - at which time I topped off the coolant and pressure tested the cooling system), one of the other tees broke completely while I was driving on the freeway. I think I explained that earlier.

If I remember correctly, the image with my thermal imager was taken after the car had been idling a few minutes with the cooling fan running on high. The temperature gauge in the car had fallen back into to the normal zone.

Or the image was taken after I had shut the car off a few minutes earlier. I can't remember. I was pretty irritated at that point.

In any case, when I replace this radiator, I will again let the car idle in the shop for about 15 - 20 minutes with my thermal imager in hand for me to see if/when the thermostat opens, how the coolant in the radiator heats up and whatever other observations I can make in that cramped engine compartment with my thermal imager. Once I am satisfied that all is well, I will road test my car about 20 miles or so.

Fingers crossed that will be the end of that as I would then like to place my order for new suspension.

 

Sounds like you have a pretty good handle on it. I know mine is a complete PITA to get the air out of every time I have to open it up. To date the cooling system has required the most maintenance out of any other system on the car. I don't have a blower though so mine is slightly less complicated.

 

As soon as you remove the radiator, you'll be able to easily check it with a garden hose for flow rate to determine if your hypothesis is correct.

 

Just my opinion, but I don't think MINIs like to idle. My sense is that the water pump is pretty wimpy, low volume. I think you need to drive the car normally to get the coolant distributed throughout the system - then do the temperature readings.

 

Any chance pieces of the broken fitting are clogging the radiator, or was it a clean break?

 

It was a clean break such that it left my cooling system wide open for the water pump to pump all my coolant out of the cooling system.

It's been in the back of my mind, but a suggestion by the shop foreman to block test my engine confirmed my fear:



This is positive block test. It means hydrocarbons are present in my cooling system. Hydrocarbons can only be present if the gases from the combustion chamber(s) get into the cooling system - like through a head gasket. The fluid goes into the tester blue and will turn green or yellow (depending on how high the concentration of hydrocarbons is) when hydrocarbons are detected. The instructions with this/these kits says the fluid will turn yellow but I've only ever seen green. Besides, when the gases from the expansion tank are being drawn into the tester, the bubbles it creates are yellow.

So now I will be preparing to pull my cylinder head, measure it for flatness and send to a machine shop for leveling/crack inspection/cleaning. I may have misdiagnosed a plugged radiator. I have a replacement radiator but have not installed it pending the outcome of this block test. I will install it when I do the head job though.

I do this sort of work on a regular basis, so this job does not intimidate me at all. I will be doing this on my off Saturdays - starting in 2 weeks since I work next Saturday. I estimate half a day to pull the head. A few days for the machine shop to do their thing and a full day(ish) for reassembly. Getting all the parts gathered may be a factor as well since I'm seeing some things I may need with shipping dates a few weeks out from now.

I'm thinking about throwing a mild camshaft in since I noticed my stock camshaft has some irregular wear on one or two of the lobes at cylinder 1 and performance cams are cheaper than a stock replacement. Maybe a few rocker arms too.

All the time, money and energy I've spent on this car over the past 14 months or so and still planning to update my suspension had brief thoughts of walking away from the car. Truth is, nothing I can afford interests me. Besides, I've never seriously considered getting rid of this car. This will just be another chapter in the book.

 

If you are pulling the head and looking at aftermarket cams, lots of power can be had from a simple port job. Check out the JCW heads. Very minor porting on the exhaust side only. Very easy to replicate. If your spending money on rebuilding a head, you may want to check out Thumper heads. I've seen some good results for the price. I have no personal experience with his mini parts though.

 

Wait what?

Why does any of this say anything other than a bad thermostat? The temperature drop in the radiator sounds more to me like restricted water flow at the T-stat than 100 radiator restrictions. T-Stats fail in the closed position.

A $50 problem becomes a $3000 problem.

Good luck,
Peter

 

Thermostat is also 1 year old. I replaced it at the same time I did the radiator but I understand it's not unheard of for a part to fail so quickly. Anyway, it's water under the bridge at this point.

I pulled my head Saturday. Certainly the easiest cylinder head I've ever pulled. I cleaned the deck surface some and measured for flatness with my precision straight edge and feeler gauges - not that I really needed the feeler gauges as I could see light between the straight edge and head deck in the center section of the head. I don't know an "official" specification for flatness but somewhere on the internet I found 0.10mm maximum. I could comfortably fit a 0.20mm feeler gauge between cylinders 2 & 3. I dropped the head at a machine shop and they also recommend new exhaust valves due to excessive stem wear. Since my camshaft has pitting and wear on exhaust lobes 1 & 2, I also need a new camshaft and at the very least a few rocker arms.

With the head off, I also decided to pull the pistons. I was pleased to see expected wear on the rod bearings for a 165k mile engine. Nothing alarming but the upper bearing on cylinder 4 is beginning to get a copper hue, so I add rod bearings to the shopping list as the rabbit hole deepens. May as well replace piston rings. Hone the cylinder wall for new rings? Here we go. Where does it stop?

As the cost is adding up, I ask my parts department to price a used long block for me. They found a 76k mile engine. All things considered, I finally told them to order it. It should arrive in about a week but I won't have time to mess with it until the second week of April. When it arrives, I'll pull the valve cover and oil pan for a look inside to be sure the engine had some oil changes in its previous life. I'm already ordering seals and gaskets so I can have a fresh start. Maybe a clutch too. And another thermostat just for kicks. And the rest of the cooling system hoses I didn't have a few weeks ago.

For those keeping track the following is what has been replaced since January 2021:
- Supercharger (Reman from Detroit Tuned) and associated gaskets
- water pump
- Bypass valve
- thermostat housing
- valve cover gasket
- belt tensioner, idler and belt
- spark plugs, coil and wires
- oil filter housing gasket
- oil cooler seals
- radiator
- condenser
- alternator
- plastic coolant tees
- most of the hoses in the cooling system

Now, what to do with my current engine as I don't believe I will need to return a core for a used engine. I could take my time and build it into a little beast to eventually put back into my car. I could rebuild it stock and sell it to recoup some of my costs. Maybe sell as is for someone to build what they want it to be.

Most people tell me to walk away from it. I guess I'm too stupid. I'd rather fix it and keep driving it than walk away and spend even more money. Stay tuned.

 

If you weren't halfway across the country I'd gladly take your old block. I drive 40k+ miles a year and need to start looking at my options for a replacement engine.
And if it makes you feel any better, I have put thousands into my wife and I's daily drivers over the last few years. All (5) of my vehicles are paid for and they are all nice (IMO) so to me its worth fixing what is broken because its usually cheaper in the long run than it is to replace it. Like you though, outside of machine shop work, I do all my own repairs/upgrades. Looking at some of the bills my buddy gets from his preferred indy shop, I'm no longer convinced fixing is always the best option if your paying someone else to do it. To each their own I guess.

Good luck with the build man.

 

Awesome. Keep the updates coming!

 

The long block arrived last Friday and my parts department let me know it was in because I told them I wanted to pull the valve cover for a quick look at the condition of the valve train.

It’s a 2006 R52 engine with 76k miles on it.



Underneath the valve cover looks clean and I was pleased to note the camshaft does not have the pitting that my current engine showed on 2 of the exhaust lobes.

I ordered an engine stand (the shop engine stand is in use) since I want to replace all the seals and working from an engine stand is a breeze.

I assembled the stand yesterday after I was done working and mounted the engine on it this afternoon after work.



I removed what was left of the exhaust manifold from this engine, really appreciating whoever rounded off the 1 exhaust manifold bolt that held it on the engine. Neither of my usual rounded bolt tools (Snap On FDX socket or Matco spline socket) would budge that bolt in spite of my liberal dousing with PB Blaster. Luckily, my neighbor technician had the twist sockets that bit right into that bolt head and easily removed it without any drama.

I also removed the intake manifold studs and then sealed the intake and exhaust ports with masking tape knowing full well my shop environment is likely a step up in cleanliness compared to wherever this engine came from after being yanked out of its original car.

I couldn’t help but look at the oil filter before I left. It’s a WIX filter and also looks like it had clean oil in it. I did see a small amount of “glitter” in the oil from the top of the filter housing but I’m pretty sure that fell in when I pulled the cap off. The oil I saw draining from the filter housing appeared to be free off any debris and so did the filter.

I was tempted to pull the oil pan for a quick look but I really wanted to head home. I don’t plan on touching the engine now until Saturday morning.

I have 3 Saturday’s before I have to work again and I would like to drive my Mini to work on my next mandatory Saturday.

My “to do list” includes:

- clean the oil & grease from this engine prior to working on it.

- replace all the engine seals (front crank seal, timing cover with oil pump seals, oil filter housing & cooler seals, oil pan & pick up tube seal, rear main seal and valve cover gaskets.

- remove engine and transmission from my car and transfer all necessary components from my old engine to the replacement engine.

- replace the front control arms (all new ball joints and polyurethane bushings)

- replace the remaining coolant hoses I did not have when I did that job in February.

- install the new engine/transmission assembly back in the car.

- install the new radiator I bought when I thought my current radiator was plugged.

I have all the parts in hand already except for the oil pick up tube seal (I think - maybe I did order it when I ordered the oil pan gasket). Including fresh oil, new filter and coolant.

For now and subject to change, I have decided to transfer my current (original, stock) clutch assembly on to this engine unless this clutch appears to be very near the end of its life. My logic is I will be teaching my daughter to drive in the next 20 months or so. I’d rather she finish off this clutch than learn on a nearly new clutch.

One issue I’ll have to deal with is when I replaced my rear bushings on my front control arms (~ 2016?), I snapped one of bolts that mounts the front, inner ball joint to the subframe. I drilled out the bolt and ran a bolt with nut to fasten it. It’s been fine all this time but I would like to try a helicoil thread repair on the subframe if I can.

I try to report my progress here maybe Sunday

 

Lookin like you got a good one. Do update

 

Well things have not quite gone to plan but in jobs like this, you always must be prepared to just go with the flow.

Last Saturday, I did get into the shop to clean the engine and replace all the seals/gaskets. Based on what I cleaned off that engine, the valve cover was leaking as well as the crank position sensor. When I pulled the oil pan for replacing that gasket, the oil was clean and there was no sludge built up in the pan so I was happy about that.



I threw the valve cover, oil pan and timing cover into the parts washer and everything was going well until I went to put the timing cover back on. I realized I am missing one of the oil pump seals that I thought I had ordered. I logged on to my FCP Euro account to see I had not ordered it. Dang it. Still being early in the day, I called both of my local Mini dealers and neither had that seal in stock and told me it was on intergalactic backorder. One of them even suggested checking FCP Euro for it but that isn't going to help me today.

In any case, I had not pushed my car in the shop as I had had a rough week in the shop already, so I wasn't highly motivated to spend my day off in the shop. I had planned to have the engine cleaned and new seals installed (except for the rear main at this point) and I would call it a day. Time spent finding the part number on RealOEM, calling the dealers, checking the internet and being angry about not ordering the part had me home right after lunch. I couldn't leave my new engine with a big hole in it, so I sealed it with tape. I guess I could have just put the timing cover back on. Here's how it sat for the next week.




When I got home, I placed my order from FCP Euro for the seal I needed and some other things I thought I might need. I paid for express shipping so that I would have the seal by next Saturday in spite of FCP Euro being 0-2 in delivering my parts by the date I requested on their order page. This is not a slam on FCP Euro, I think it has more to do with FedEx dropping the ball as I live in Arizona and FCP is in Connecticut. Their website indicated that oil pump seal would ship in 2 days, so I imagined Wedneday I would receive shipping notification. Imagine my horror when I got that notification on Friday. So now then engine would remain in this state for another week.

As much as I did not want to, I got up yesterday morning hungover from a neighborhood party Friday night and went into the shop. My goal was simply to get the engine and transmission out of the car and then separate them so I could have a look at the clutch. Aside from breaking one of the bushings on one of the shifter cables, everything went fairly well. Inspection of the clutch assembly found it in good condition with no heat spots on the pressure plate or flywheel, which isn't surprising considering we have owned this car since new and I can't think of a time I ever race launched from a dead stop. The term "adult driven" comes to mind. Closer inspection of the friction disc found maybe 2mm of friction material before the rivets would be flush with the friction material.

Wife asked me if this clutch would make it another year. I said maybe but the more I thought about, I decided to not even worry about it and just order a new clutch. It's just way too convenient to not install a new clutch right now.

After debating whether to install a Valeo SMF conversion clutch kit or stick with a DMF and in spite of all the good things I've heard about the Valeo SMF conversion, I decided to stick with a DMF. So I ordered an LUK dual mass flywheel and clutch kit. My reasoning is I don't want anything to be different with a new clutch out of concern the wife not might like the different feel of a SMF. I suppose I'll have another 100k+ miles to consider an SMF conversion for the next clutch. So with the new clutch, new bushings for the throwout bearing fork, a new input shaft seal and a new shift cable on order, I'll wait for those parts to arrive. I did not choose expedited shipping this time since apparently no matter how much I pay, FCP Euro cannot get parts to me by the next weekend. So my car is riding high now without the powertrain.



Next Saturday, all I can really do is install the timing cover since that parts delivery should be here tomorrow and then I'll also replace all the remaining coolant hoses that I did not have previously. I do not expect to be highly motivated as 6 days in the shop per week since February is burning me out, but if somehow I get a strong cup of coffee, then maybe I'll go ahead and put on the new front control arms (with bushings and ball joints) I have sitting in a box in the shop. I work the following Saturday, so I expect that clutch and shift cable will be here the week after that so the Saturday after that (in May now) I can replace the rear main seal, install the clutch, replace the shift cable and mate the engine and transmission then get the powertrain back into the car. Maybe get the radiator that's been sitting in my car since February installed too. So my new target is mid May for engine start up.

For now, my car has a hole in it.


And my powertrain sits in pieces on the floor for another week.


And because this repair on my own car isn't enough to keep me busy apparently, I noticed my wife's car dripping oil on the garage floor. Quick diagnosis found the front cam seals are leaking. So I'll be ordering both VVT units, cam seals, front crank seal, water pump and timing belt kit for that car for repair in late May.

 

 

Man - wish I had that kind of space to work! Nice to see such good care being taken of another r53. I know there are several of us who plan on keeping these little cars forever. Looking good!