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R50 Engine Fault Finding.

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I know this is quite a long post, but thought it may be of help or interest.

 

Bought a MINI ONE 2001 with things to do. It is in very good condition for its age with grooved discs and pads to match and lowered, but not extremely. Under the bonnet it has SAMCO hoses fitted. Digging further it also has a Cooper ECU is in place and some type of performance exhaust, louder than standard, but not too loud. Sounds quite nice.

 

I knew buying a cheap older MINI would probably throw up a few issues, but working as an engineer most of my life I was not daunted in the least. The last time I have enjoyed working on a vehicle this much since I had motorcycles, which I stopped riding six years ago.

 

I have been lucky with my MINI, all the problems have been niggly except for two which may have been related, but found weren’t. The engine surging when warm, ticking over between 1000 and 1500 RPM and hanging onto revs when changing gear or dipping the clutch. Also when taking your foot off the throttle it had a pronounced jerk. There is no engine light, and no codes were thrown up, and it ran fine, but a little heavy on fuel, about 30mpg. Also the coolant was bubbling in the expansion tank, so first thoughts were the overheating may be the cause of the problem, but the temperature gauge never went past half.

 

I decided to change the thermostat, housing, and temp sender anyway. When removed they looked to be the originals. After topping and bleeding the coolant the engine was brought up to temperature, still the coolant bubbled in the expansion tank. When running the engine I noticed the 1st speed of the fan did not kick in only the 2nd, the resistor has gone on 1st so need to replace this, but not to bothered at the moment as it is winter.

 

Next I replaced the thermostat cap, problem solved, but still the engine surged. The obvious cause now  would be a vacuum leak, but visually everything was OK and spraying brake cleaner on all the pipes joints and couplings when running didn’t cause any change to RPM, so what signals does the ECU need from what for fuelling? MAP sensor, Pre-Cat O2 sensor, Post Cat O2 sensor, Throttle Body to control inlet fuelling.

 

Next thought MAP sensor as this measures the manifold absolute pressure which the ECU interprets for fuel delivery. This I replaced but very little difference; next I replaced the O2 sensors, still no discernible difference. I took off the throttle body now, the flap and body were gunged up so I replaced it, still no difference. I have since cleaned the throttle body, good as new, and I have a spare.

 

Now I am scratching my head, could it be the fuel filter or fuel pressure regulator? I ordered a new filter but found it is the wrong type. I was told a cartridge was needed, but a canister type is fitted, so still need to do this little job, so moved onto the regulator. Out of curiosity I sprayed brake cleaner on the regulator when the engine was running, no change, but by accident some brake cleaner got on inlet manifold where it joins the head. Eureka, the Reves changed, the inlet manifold gasket had failed and was sucking air.

 

 I ordered a full manifold gasket, and 10 came, more spares. When I removed the Inlet manifold I found it had a full gasket fitted but the manifold has grooves for the prevision for the four separate rubber ‘O’ ring type gaskets but there was none in place. So as very little heat is in this area I ran a bead of silicon instant gasket in the ‘O’ ring grooves as well as fitting the full new gasket, ensuring none of the instant gasket fouled the inlet, or injector orifices. Reassembled and started the engine. The engine immediately sounded quieter and happier. I allowed the engine to come to temperature and tickover settled at 800rpm, no surging. Took the MINI for a run, it is now more responsive, smoother and quieter, a completely different car to drive.

 

These issues are now fixed, but still have to sort the heated rear window and mirrors, the radio and speakers are rubbish, and someone previously deleted the rear wiper and washer. Don’t get that, the rear of the car is a muck magnet.

 

I love this car. When I have fully sorted it out to my satisfaction I will give it to my Daughter and get a R53 Cooper S.

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What a write up, wish i could read a lot more stories like this. As i was reading he issues you had i was instantly thinking inlet manifold, was so happy to see later on you sorted that exact issue out. I didn't even know there was a single gasket available for this model, unless it was made out of gasket paper lol

 

So happy you are sorted now. I always found the Gen 1s with the Cooper ECU revved super well, especially with a good rorty intake :)

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To be honest if I had given it more thought I should have arrived at the inlet manifold a lot sooner but I was having so much fun learning about the car, and I intend changing the sensors anyway I just went through a methodical approach.

 

Yes you can get a one piece pressed steel gasket with raised sections fitting in the grooves of the manifold.

 

What I do need is a specific code reader and reset tool that will cover 1st and 2nd generation MINI’s, as the one I am using at the moment is for my Mercedes and only shows generic faults and codes. Any suggestions at a reasonable price?

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I was thinking inlet manifold all of the time too 🙄

 

As for code readers, a lot of us use "Carly for BMW" not a huge amount of functionality with Gen1's but more with Gen2's and more so with Gen3.I can be used for diagnosis and coding. 

They now do a universal adaptor and have apps for many marques, BMW, Mercedes, Porsche, Toyota and a few more i'm sure. I bought this some 4-5 years ago when the price was under £10 and a universal adaptor worked. now i think the adaptor is around £60 and the app on top

 

Others use Bimercode, 

Similar functionality to carly i think.

 

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That was a good read.

 

The Ones and Coopers used to share the exact same Engine Ecu, however the Mini one had software in it that restricted the throttle to only open around 75%, but the cooper allowed full 100%, giving the peak power difference between them.

if it’s an ecu from a cooper, the ews unit and keys would have had to been swopped too.
Dealer programming would let you put cooper software in, but most people just got an external remap done which released that power and a little more.

 

the only 2 gaskets are the individual rubber o rings for the plastic one/cooper manifold, or the single metal gasket which is for the cooper s with the aluminium manifold - ebay list them as all same but aren’t quite right, if you check realoem.com you can see the difference to what should be there.

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Thanks for the information Stevemini.

 

The MINI I have acquired has been in the same family since new, as everything works I would assume when the Cooper ECU was fitted it was programmed in by MINI as everything works as it should.

 

As for the inlet manifold gasket, what you say makes sense, but the bead of silicone in the groove with the new gasket metal gasket has worked fine. When I have the need to take off the manifold again I will replace with the rubber 'O' Ring type. I have 9 spare metal gaskets now, good job I plan on getting an R53 lol

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