N52B25 vs M54B25 for reliability.

[Magicarcher]

Hi I am trying to decide between a 2005 M54 2.5L and a 2006 N52 2.5L. I am a little nervous about the N52 reliability. It appears to have a number of issues which are reported as being quite common.

1. Electric water pump failures
2. High oil consumption due to piston ring problems and valve guide seal deterioration which can lead to catalyst damage.
3. Hydraulic valve problems

How common are these problems in reality?

 

[srhutch]

You are going to get many different opinions on here.

I had an N52 and suffered the HVA issue, http://www.z4-forum.com/forum/viewtopic.php?f=3&t=10937

Personally I would say the M54 is more bullet proof, easier to work on. The N52 isn't very day friendly being valvetronic.

The M54 also has more tuning options.

 

[Llewelyn]

Is there a reason you want a 2,5 liter car? 3,0 is a sweeter engine in M or N and probably the same on fuel....

 

[Mr Tidy]

I've had BMWs for over 10 years, but only escaped from diseasels 2 years ago.

My limited experience relates to a 3 litre N52 in my Z4C and a 2.5 litre M54 in my 325ti, but FWIW the electric water pump on my first Z4C died last December at 9 years old. An OEM pump cost £500 and a thermostat another £100 plus fitting at my local BMW specialist, so the bill made my eyes water a bit!

But my 325ti got a complete cooling system refresh (new radiator, temperature sensor, expansion tank and aux. drive belt) and the bill from the same specialist was just over £400 including fitting.

As someone has said why not go for a 3 litre M54 - that looks like the best of both worlds to me! But sadly the Coupe never had that, and my Z4 just had to be an E86!

The N52 is a terrific engine, but there is potentially a price to pay - mind you if you found one that had a new water pump that may give you some reassurance, although as someone else said there can still be Vanos issues.

I supposed ideally it would be good to try all of the options - good luck anyway!

 

[Magicarcher]

Hi Llewelyn, the reason I am looking at a 2.5L over 3 is budget. Pound for pound I am finding a 3L is a couple of years older and 50% more mileage than a 2.5 and I would like to get as low a mileage and age as possible. Otherwise would love 3L. There are also less of them around, so much harder to find.

 

[csl1973]

I know the M54 engines like oil as a couple of my mates found out, not heard of the N52 using oil and mine has always been good. Yes water pumps can fail on these engines, but the M54 engines also can suffer too from a failed pump as these are plastic and prone to failure as they get brittle and crack with age. The hva issue is around, but regular driving will keep it at bay and the N52 is in a lot of cars and some with many many miles and still going without issues or failure of any engine. So don't be over concerned about the issues, all cars have problems as they get old and all cars cost money, unless you never use it and just store it away.

 

[Steve84N]

My old M54 on 110,000 miles used to use a fair bit of oil to the extent that if we were doing a long trip to France and back it would be prudent to take a litre with us. The N52s we have now in the Z4C and e91 both use a small amount but it's less than 0.5l in a few thousand miles. I had the breather pipe done on the M54 but it still used oil.

There's no real deciding factor reliability wise so I'd say get the N52 as it's more powerful and certainly in 3.0 form I think it's a nicer engine.

 

[Smartbear]

The n52 doesn't commonly suffer from piston ring/valve guide issues, oil burning issues are normally caused by a clogged up engine breather system the same as the m54.
Short journeys & bmw's overly long oil change interval increase the odds of this happening.
The n52 has improved disa & vanos systems according to bmw, the earlier m54 suffered problems in both these areas, don't worry about the 3litre covering more miles for your budget, they are tough & can take it.
Neither engine is perfect, they just suffer from different problems, as previously mentioned the n52 water pump is pretty expensive when it goes (but an easy diy)
Rob

 

[goldbcfc]

Hi I am trying to decide between a 2005 M54 2.5L and a 2006 N52 2.5L. I am a little nervous about the N52 reliability. It appears to have a number of issues which are reported as being quite common.

1. Electric water pump failures
2. High oil consumption due to piston ring problems and valve guide seal deterioration which can lead to catalyst damage.
3. Hydraulic valve problems

How common are these problems in reality?

The m54 was widely used in more bmw vehicles and is easy to work on having less over engineered parts like n52. There's the price of parts being a lot higher take the waterpump on a n52 £350+ and the M54 waterpump is £35. Bad oil consumption in m54 is usually a £20 gasket or a blocked CCV system. It can be replaced for £80 hardly worth mentioning really, using thicker grade oil 5w40 should help too. The n52 does have approx 30 bhp more power but the facelift Z4 was also heavier than the pre facelift Z4 with m54 engine. So its horses for courses do you want a car 0.2s faster 0-60 or a reliable engine that's 0.2s slower. I'm now on my 4th bmw with a M54 engine its a matter of start each morning and drive has been for the last 10 years costing very little to maintain. When I sold my 330ci in 2014 the plan was to buy a 6 series so I looked into a getting a 630i. It was then I found out it also had the n52 engine fitted so I checked 6 series forums and it was well documented the 630i and its issues. The only good thing I can think of is the was fact it was the lightest 3.0i engine made by any car manufacturer at that time and did win awards. Knowing all this I still went and bought another bmw with m54 engine being a Z4 3.0i. It doesn't use any oil it came with 3.5 litres of castol bottle from last owner and I've only just finished the bottle after 6 months driving daily. I really cant see anything going wrong with yet another m54 engine car im owning in all honesty TBH..........."M54 is BULLETPROOF" fact