The meat: 2003 MCS with 100k. Took the car in to the dealer for CEL, found low compression on all four cylinders: 125psi-100psi-75psi-125psi. The car has consumed oil at a rate of about 1/2 quart every 5000 miles for years with a bit of smoke after sitting, and a small oil leak (a drop every few days) that no mechanic ever seemed to be bothered by. Car seems to run fine, no harshness or obvious misfiring (though the code reader started telling me that I had a misfire when the CEL came on. NO visible oil/coolant mixture (I have always changed my own oil - just did it a month ago).

Dealer suggested replacing the head, valves, injectors (and associated parts), which with labor would be more than $5500. I can't afford to replace the car, nor can I afford that repair cost. I'm looking at used lower-milage heads (not rebuilt) and a rebuilt head. I'm trying to assess whether or not it will be worth the trouble, and what else I am likely to run into in the process.

Thank you in advance for any suggestions.

p.s. anyone have a shop to recommend in/near Fredericksburg VA (close to both DC and Richmond)

 

Interested in other responses.

Synopsis: CEL on; code indicates misfiring. Diagnostics show low compression, with one, possibly two cylinders out of spec. No history / behavior of oil burning under load, rings/cylinder walls not indicated.

From what you've described, the head isn't damaged/warped/unusuable, so why replace it? Instead, pull the head, have a machine shop do a "valve job" (resurface seats, replace valves as needed or recondition, replace valve seals), check for head sealing surface in spec, mill slightly if required. Re-assemble. Head R&R + the valve job cost. For quite a bit less? [Really, not different from the rebuilt head option that you mentioned].

Injectors have moving parts that wear (seems plausible, some needle/seat component that controls fuel flow)? Why are they wanting to replace those at 100k? Just a precaution, or "while we have it apart" logic?

More questions than answers, sorry, I'm learning about MINIs and how other automotive experiences might apply (or not).

 

THe logic is this: low compression means that the valves are not seating properly, which means air can be sucked back in, causing a lean condition. Alternatively, if the injectors are causing a lean condition somehow and affecting the valves. I don't know- I think they were giving me a worst-case scenario. I found a shop to clean and check the injectors for $21 each, so I'll be going that route if I do this myself. Problem is, I don't have the equipment to check the head for warp.

 

You took it to a MINI dealer, correct?

1) I would be asking them how they have determined that the valves are not seating compared to worn piston rings?

2) I would be asking them what the results were on a cylinder leak down test compared to a compression test. The leak down test will primarily test the sealing of the valves in each cylinder.

3) I would be asking them what the cylinder walls looked like by viewing with a boroscope. If there was scoring or any deep gouges on the cylinder walls that may indicate worn rings or damaged cylinder walls.

4) I would be asking them what cylinder(s) set the misfire fault. Misfire faults come up P0300 (random misfire) P0301 (cyl 1 misfire) P0302 (cyl 2 misfire) etc. etc. up to P0304 for the 4th cylinder. If you only have one cylinder misfiring and it also happens to be the cylinder that only has 75psi for compression then that would narrow things down, versus having a random misfire.

5) I would be asking if they were able to duplicate the misfire and if so what cylinder they traced it to.

6) I would be asking if they performed a fuel pressure test and also noted if they checked for fuel pressure leak down after shutting down the engine. This may indicate leaking injectors which can be seen with wetness/fuel in the cylinder viewed again with a boroscope.

7) I would be asking whether they have determined if the injectors have caused the misfire or whether the faulty cylinder head has caused the misfire.

8) I would be asking if they had a fuel injector cleaning service and also if the valves and head gasket could just be replaced instead of the entire cylinder head.

Since the head is being suspected as faulty, I would ask if a coolant pressure/leak test was performed to see if there was any coolant leakage into a cylinder (can be checked again with boroscope down spark plug hole looking for coolant/wetness in a cylinder when cooling system is pressurized to 15-20psi). This will determine if you have a possible cracked cylinder head.



Also, keep in mind, Dealerships are not in the business of rebuilding or machining things back into specifications. Anything that is suspected as faulty is quoted for replacement, NOT servicing. This is not a bad thing, its just called covering their butts. Obviously they suspect a faulty head but that is NOT enough information to go off of. It needs to be determined if the entire head is cracked or warped. If it is warped the only way they could determine that would be to remove the head and use a straight edge with feeler gauges to determine lack of parallelism on the surface.
***Unless you paid hundreds of dollars for diagnosis in order for them to disassemble and remove a head then obviously they have not checked for warpage.

If they only suspect faulty valves, then I would ask them to just quote those. Most dealerships have a fuel injection cleaning machine where they run the engine and it disperses an injector cleaner though the fuel rail which runs it through the injectors.

But quoting both a head and injectors seems to me that perhaps they are stumped and guessing or that perhaps you have multiple issues. Perhaps low compression/cylinder leakage from faulty valves and misfires from clogged or sticking injectors.

Ask the questions I have mapped out for you above and try to get more answers as to what the diagnosis has revealed with your engine. From there you will be better informed as to what your next steps should be...machine shop cleaning head and replacing valves then reinstall head with new gasket, replacing or cleaning injectors as you have mentioned, etc etc etc.

 

Also, the reason nobody has tossed red flags at your oil consumption is because most manufacturer's oil consumption specifications are ridiculous. Audi is 1 qt every 800 miles. Mercedes is 1qt every 1000 miles. Ford and chevy I believe are around 1 qt every 750-1000 miles. Most all manufacturers have faced class action law suits during some point over oil consumption, so they all have ridiculous specifications for what is ''tolerable'' to have to avoid responsibility for anything being 'wrong' with their engines that consume oil.

Your consumption comes out to being 1 qt in between oil changes essentially, which honestly is not bad. A little blue smoke after start up may indicate leaking valve stem seals. Blue smoke on hard acceleration could also be valve stem seals or faulty oil rings on the pistons. Based off the low compression I'm not entirely convinced that you have a valve problem vs. a piston ring problem but as I said above, ask more questions to see what you're actually dealing with here.

 

Erik- THANK YOU for taking the time to write this all out. I am going to send these questions to my Service guy right now. I can wrench, but I'm not experienced at diagnosing problems, especially complex ones like this. The impression i got was that they threw a worst-case scenario number at me (probable cause) and gave me the impression that they couldn't be sure without taking the head off. It sounds to me that there is quite a bit more they could have tested to narrow things down a bit. As far as I know, the slight smoking only happens at start-up. I've never even noticed it- a friend told me a while ago.

I completely understand the dealership policy of replacing parts rather than machining them. I'll see what the dealer says, and keep this list of questions for when I take it for a second opinion. Thanks again, and I'll post back when I know more. I'll check the fault codes this evening and see where they fall. O believe it was reading P0300, "misfire on multiple cylinders."

-Josh

 

I'm curious to see if that compression test was a dry test or a wet test. If the numbers are from a dry compression test, then I can see how you don't notice the misfires while driving. At 75psi you should definitely notice the misfires, especially under load.

I also 2nd doing a leakdown test. That'd better pinpoint where the compression loss is coming from, the valves or the rings.

 

What was the CEL code? I would have the compression test redone or
do a leak down test with someone other than the dealership. Could be a head gasket leak between cylinders?