Hello all, some of you may have seen my recent post about picking up that 2005 R53 for $600 that needs a head gasket. Car has 150k miles on it.

So today, I just got the head off and indeed there is coolant in the cylinders, and the motor oil is slightly milky. The previous owner put K Seal in the coolant to attempt to fix it btw. I’m going to take the head to a machine shop tomorrow to get pressure tested and resurfaced if possible. I know that the Bentley Manual states that the maximum amount of material you can remove is .012” (.3mm). I’m hoping the head will still be usable. I’ll also check for bent valve stems on Cylinder 2.

That being said, after removing the head and drying up the cylinders, I see that there is a dent from a valve in Piston #2. I’m going to have to replace that piston. What is the best/easiest way to remove and replace the piston? Do I have to remove the whole block to do so or is there a way to do it with the block still in the car?
I’m also wanting to know the best websites to get decently priced pistons. I see that a Mini branded replacement is around $300USD and “performance” aftermarket sets of 4 run around $600+USD. I’m aware that piston weight and engine balance is a factor, so if going aftermarket, all four should be replaced together. Would I be able to just pull a single piston from a parts car/junkyard car engine to maintain balance? I’d also want to change the rings in all pistons since I’m already going to be in there. I believe that honing the cylinders is recommended when replacing the rings. Do you guys have any tips, advice, or helpful info when it comes to replacing pistons and such on these cars?

Attached below are photos of the pistons, the head, and the gasket. I noticed there’s a bronze colored area at 6 o clock on each piston and appears to not have carbon buildup in that spot.



Cylinders full of coolant w/ K Seal in it^


Piston #2 dented by a valve ^



Cylinder Head side of head gasket^


Block side of head gasket^

 

A single factory piston would work fine since you're not doing a completely balanced build / rotating assembly.

Yes, you can do it with the block in the car, and yes, even without doing Rings, I'd do all the rod bearings.
Simply pull the pan, un-bolt the Rods, and push the Pistons out the top.
Use great caution to not hit the crank on the way back in, and upgrade to ARP Rod bolts, while your at it.

As an FYI, you can do almost anything to the motor with it in the car. Just not Crank or Main Bearings because of the Split Block design.

Honestly I'm a little surprised that the damage is there, these being non-interference motors. I'm thinking it may have dropped a valve before, and you're not the first person to have the Head off. But at this point it really doesn't matter one way or the other.

 

Excellent! That’s all pretty relieving to know. Those tasks seem easy enough. I’m glad that I don’t have to pull the block out for all of that. I’ll definitely pull the pistons then, and change the rod bearings and piston rings.

I’m thinking the same thing with that damage from the valve. Should be good as new with everything changed out. I’m hoping the head is good and not warped, I guess we’ll see. I’ll have to get a replacement head from a junkyard car ($160) or one from AllMag if mine is bad.

There is a loud exhaust leak somewhere near the manifold but I couldn’t find anything after getting the head out. It could’ve been the manifold gasket. I’m gonna unbolt the flange and take the exhaust manifold out and check for cracks. The seller said quote: “Exhaust leak due to hole near headers, idk what caused this”. This is the same guy that thought K Seal would fix this engine. I looked at the back of the block and didn’t see anything.

 

Also take a good look at the flex basket if that Header has one (I think you said in your "find" post, that it has an aftermarket Header) common cause of leaks, esp without an upgraded to motor mount.

 

Yeah I’m gonna check that part out. In the listing, the guy said it was aftermarket but after I got the car and looked, it’s just the stock manifold actually. It was a dumb twenty-something year old that owned the car before me

 

So…. It’s got a dent. I would rotate and see if all pistons get to the same height at TDC - for each one. That will let you know if the connecting rod is bent. Hondas are know for this. I don’t know if Mini is. If nothing is bent, part of me would say put a fresh head gasket on, and a good head.

 

https://www.northamericanmotoring.co...with-pics.html

for Cat issue. Mine is fixed that way. Not CARB compliant.

 

https://www.northamericanmotoring.co...with-pics.html

for Cat issue. Mine is fixed that way. Not CARB compliant.

 

^^ This ^^
Figure out a way to measure the rods some how, if you're reusing them.

For some reason I thought he was swapping complete Rod and Piston assemblies, this was a good catch to cover my assumption.

In an NA motor I'd actually do the measurement and run that piston, if the measurements checked out, with just new Rod Bearings all the way around, but in an SC application, the extra heat would give me pause, thinking it's created a weak spot.

 

That is an odd dent. Not likely valve contact - placement is wrong. Maybe a spark plug chunk, and that is why the head came off. I once had a Volvo V6 that I got - bent valve, stem chunk bounced around inside. I cleaned it out, put back together- drove for 120k more. That was in 1987…..

 

Good idea, I’ll check that. Yeah with this car, I really don’t know anything about its history. The guy I bought it from got it from a buddy only a month ago. He said the car has a tune so I’m not sure if it was done properly/safely. I have no idea who or how they tuned it 😬 Intake, exhaust are all stock, and it doesn’t look like a smaller supercharger pulley so idk why they’d tune it. But yeah, idk how much they drove it with the blown head gasket.

 

That is a good observation, looking back at the pics of the piston and the head, it seems like it’s in between where the valves would touch if they did drop, I would think 🤷‍♂️

 

Would swapping out the piston rings be highly recommended or just “optional”. I read through a bunch of threads on the forum here and read conflicting things. Some say that if they’re not worn out and if tons of oil isn’t being burnt, it might be better to leave the factory ones because they’re bedded with the cylinder? I also read that honing may not be necessary?

 

We've seen motors with minimal oil "usage" at even 250-300k, so it really depends.

Honestly, it's just a matter of how comfortable you are with doing all the associated work.
If it were me, and I was going to risk that piston, I'd just do the Rod Bearings and send it (lower end that is)

But I'm very comfortable with the work involved and have no problem ripping back in if it doesn't work out.

But if you're changing that piston, you might as well do the Rings as well.
As long as there is no scaring on the cylinder walls, (esp where that damaged piston is) I'd leave the walls alone. But, if your leery of that, the only honing I'd consider is a quick rough up with a Ball Hone (again depending on cylinder wall condition, mine still had some light hatch marks at 213k) just remember to cover the Crank under each cylinder, to keep it from getting dusted.

 

It does look spark plug sized. Also i am curious about the triangle looking marks on cylinder 3-4, have had several R53 engines apart and never seen them markings? anyone?

This is what my pistons look like, nothing regarding them weird markings center of his pistons?

 

i dunno...it looks like that dent has been there a while. i don't think i'd replace just that one piston. i think i'd either leave it or rebuild the entire bottom end.

that's not a fresh dent. it's got carbon buildup on it that matches the rest of the piston top. i like the idea of measuring the rod length. but otherwise....

you've got a $600 mini. i mean...the risk is minimal. i'd be tempted to send it. and then if it fails, then decide the next steps...

 

@Stormrider84 Check the oil cooler while your in here, its famous for breaking down and causing oil and coolant to mix which in turn looks like a head gasket issue. Its not to difficult to remove from the right wheel well if your this deep in already!

 

Do you think that running that piston could cause problems down the line? I know there’s the potential for hot spots/localized overheating.

If I do leave the dented piston alone, I’ll leave the rings alone and just do the rod bearings

 

Good to know! The oil cooler is right behind the oil filter right? It was a pain getting that timing chain tensioner bolt out because of it in the way lol

 

Lol yes been there, its easier if you remove the oil filter and cap but still a nuisance to remove the tensioner.
There is 4 torx head bolts holding the cooler onto the oil filter housing, the bottom right one is a bugger to get onto to squarely so be careful. I once had to use Ez-outs to remove one of these and it was no fun! Really helps having wobble extensions here!

 

Yeah it was definitely easier to get to that bolt after I removed the filter and cap but was still hard to get off even with a swivel adapter haha. It’s hard to get enough torque to the bolt with that swivel at that angle. But it came out, so I’m happy haha. Where does it usually leak/fail at on the oil cooler?

 

Honestly, with just the piston, hot-spotting would be my only concern, creating a slight weak spot. But under normal usage, in non-race use, I wouldn't worry about it too much. (Again, with no cylinder wall scaring, and no rod damage)

But, if you do use it as is, (with just a rod bearing change) the first thing I would do would be to get it tuned, if nothing else to lessen the chance of detonation, which could obviously exploit that area of the piston.

With my comfort level I look at it like this, if it doesn't work out, you're most likely not going to damage or replace anything you weren't already thinking about buying, and the only extra would be the time, and the cost of a head gasket set and oil. But again that's me, and I can do a head gasket change in a day, and the rest of it in a weekend if all the parts were already there. So it really just depends on if you don't mind going back in if you need to.

 

It usually fails internally, for me the return pipe coming off was visually plugged. I assume the best way to test for a leak would be to remove it and run water through, although it wouldn't build pressure so not fully accurate. I guess it could be pressure tested with some cobbling of bits.

For me I just replaced the cooler while I had everything apart for peace of mind, they aren't all that expensive!

 

Thanks for that advice. That’s a good way of putting it. It wasn’t difficult at all or time consuming getting the head off so it wouldn’t be the end of the world if I ever had to do the job again in the future.

So far, I’m going to replace the obvious gaskets, timing chain and guides, probably the tensioner, spark plugs, and the rod bearings. Still deciding on the piston. I’ll probably hold off on the rings if I keep the dented piston. I’m waiting on seeing if my head is good as well. I really don’t want to buy another head but we’ll see

 

Yeah I have no idea what those marks are. They almost look the only areas not caked in carbon. Idk if it’s possible, but could the K Seal in the coolant have caked onto those parts of the piston? Idk if that’s even possible. But yeah those spots are bronze colored and there doesn’t appear to be any caked on carbon in those spots. These pistons are really caked up too.