Hot engine smell

Glen_Quagmire

I have a 2006 BMW 523i petrol with 130k miles which I bought a few weeks ago for small enough money. I've noticed the engine area gets very hot and there is a noticeable "hot" kind of smell when I stand near the bonnet or open the bonnet. There is no smell while in the car driving or no warning light to say the engine is overheating.

Is this the norm for this type of car or what could it be?

Also noticed there is a tapping sound when the engine is cold which goes away after a few mins when the engine heats up.

Again, is this expected or what should I be on the look out for?

Alanstrainor

It's hard to say really. I would wait until the engine is coo and check your coolant level. Then I would check the oil level and make sure both are in good order. If you've not owned something like this before it could just be that you're not used to it. But there could be something amiss.

As for the hot engine smell, I wonder if what you're actually smelling is oil burning, things like the rocker cover gasket could need doing. But so could a lot of things at that kind of mileage.

Check the above for starts and see how you get on.

Glen_Quagmire

I checked the coolant and it is low alright, however if the the coolant was low and the engine was running hot I would expect to see a high temperature notification but I haven't?

Also, there is evidence of oil around the engine so looks like a leak is or was there at some point in time.

Does this sound bad??

I only need the car another year or so before getting something new

Alanstrainor

Glen_Quagmire wrote: »

I checked the coolant and it is low alright, however if the the coolant was low and the engine was running hot I would expect to see a high temperature notification but I haven't?

Also, there is evidence of oil around the engine so looks like a leak is or was there at some point in time.

Does this sound bad??

I only need the car another year or so before getting something new

If the coolant is low then you most likely have a leak somewhere. It's expected in these cars at that mileage. As for what it is, its very hard to say. I suppose it depends on how bad the leak is, but personally I'd want it sorted. Low coolant doesn't mean that the engine will over heat, at least not while it is only slightly low.

As for the oil you can see, if it's around the top, near the rocker cover then I would think the gasket needs doing. Again, at that mileage this isn't surprising. It will leak oil, and give a burning smell.

I drive a 325ci, I've been around the block in terms of coolant and oil leaks!

Glen_Quagmire

Alanstrainor wrote:

If the coolant is low then you most likely have a leak somewhere. It's expected in these cars at that mileage. As for what it is, its very hard to say. I suppose it depends on how bad the leak is, but personally I'd want it sorted. Low coolant doesn't mean that the engine will over heat, at least not while it is only slightly low.

Alanstrainor wrote:

As for the oil you can see, if it's around the top, near the rocker cover then I would think the gasket needs doing. Again, at that mileage this isn't surprising. It will leak oil, and give a burning smell.

Alanstrainor wrote:

I drive a 325ci, I've been around the block in terms of coolant and oil leaks!

Grand sounds like it's a common thing so.

What I'm getting at is, does it sound like the car is on its way out or will I get another while out of it? The car drives smoothly and no other issues apart from a stater motor which acted up a few weeks ago which I need to get replaced as well.

Trying to decide whether to put money into getting it fixed or cut my loses and get something else?

corks finest

Glen_Quagmire wrote: »

I have a 2006 BMW 523i petrol with 130k miles which I bought a few weeks ago for small enough money. I've noticed the engine area gets very hot and there is a noticeable "hot" kind of smell when I stand near the bonnet or open the bonnet. There is no smell while in the car driving or no warning light to say the engine is overheating.

Is this the norm for this type of car or what could it be?

Also noticed there is a tapping sound when the engine is cold which goes away after a few mins when the engine heats up.

Again, is this expected or what should I be on the look out for?

Probably oil leak burning smell

Alanstrainor

Glen_Quagmire wrote: »

Grand sounds like it's a common thing so.

What I'm getting at is, does it sound like the car is on its way out or will I get another while out of it? The car drives smoothly and no other issues apart from a stater motor which acted up a few weeks ago which I need to get replaced as well.

Trying to decide whether to put money into getting it fixed or cut my loses and get something else?

None of my guesses of these problems are terminal. They're all fairly standard and nothing to be afraid of really. How much did you buy the car for? Are you going to attempt a DIY?

Leonard Hofstadter

BMW six cylinder engines run quite hot compared to other makes (they have a map controlled thermostat and under normal driving the coolant temperature can be as high as 110 degrees depending on the engine - whereas a conventional petrol engine normally runs around 90 degrees), so I wouldn't worry about it - unless it's a burning like smell. If it's a burning kind of smell then it's either the rocker cover gasket (as Alan said) or the oil filter housing gasket, some BMW petrol engines are dynamite for these problems although I didn't think the engine in your car was prone to it.

If you're doing it yourself you need to buy the parts from the OEM supplier or BMW themselves - not sure how much they are for an N52 engine but on the older six cylinder engines the rocker cover gasket is around €60 and the oil filter housing gasket is about €5. Whichever one it is, I would definitely fix it. At a garage, the rocker cover gasket should be about an hour's labour while the oil filter housing gasket should be about 2 to 2.5.

Regarding the noise, if it's just a ticking sound when starting up then those engines are notorious for it, they have a problem with the hydraulic tappets losing oil pressure after the engine is turned off. The ticking sound is caused by this; it disappears once the pressure has built back up.

https://en.wikipedia.org/wiki/BMW_N52#Lifter_noise

If it sounds like what's described in the link I wouldn't worry about it, if it's a louder noise and it goes on for a few minutes then it needs to be looked at.

Bmw123d

I would be fairly sure that ur vacuum pump is leaking on to the exhaust. But as stated these engines do run quite hot which isn’t a issue. There might not be a leak just because the violent is abit low. Then the rocker cover gaskets on all bmw engines do tend to leak.

Glen_Quagmire

Alanstrainor wrote:

None of my guesses of these problems are terminal. They're all fairly standard and nothing to be afraid of really. How much did you buy the car for? Are you going to attempt a DIY?

Only paid 2250 for the car, its very clean inside and outside. Only problem to date was that time it wouldn't start but a few taps on the starter motor and away it went. Has started every time since. No I won't be doing any DIY. I wouldn't have the time or patience or tools. I'd happily pay a mechanic a few quid to do it right.

Dropped it off at the mechanic today anyway, he said I could probably get away with not having to replace the starter motor and just give it a tap of it happened again but sure peace of mind to just get it done.

Hopefully the coolant leak isn't a big deal. Forgot to ask him about the tapping noice when it's cold too, that'll have to wait till next time I suppose

Glen_Quagmire

Bmw123d wrote:

I would be fairly sure that ur vacuum pump is leaking on to the exhaust. But as stated these engines do run quite hot which isn’t a issue. There might not be a leak just because the violent is abit low. Then the rocker cover gaskets on all bmw engines do tend to leak.

When people get these small oil leaks do they always get them fixed or just top up when the oil gets low?

I seem to be topping up with a litre or so every 1-2k kilometres but I read that these engines are notorious for going through oil.

Leonard Hofstadter

Yes, I would definitely get the oil leak fixed, it's not expensive to do and hot oil could set the car on fire if it touches for example the catalytic converters!

Being tight with maintenance on a BMW is not a good idea, it will cost you more money in the long run and they do not take kindly to skimping on maintenance.

Regarding the oil use well if it's leaking that will definitely affect it for sure. I don't know a lot about the N52 engine yours has because mine uses the older M54 engine. However, the M54 is notorious for oil use because of the low tension piston rings and they normally start to use quite a bit after 100,000 miles. It's considered 'normal' for that engine to use up to a litre of oil every 600 miles. Make sure you're using LL01 spec fully synthetic from a good quality brand. In the M54 engined cars changing from 5W30 to 5W40 will cut it down a bit but it will still use some. Yours isn't the first N52 I've heard of that uses oil so I'd say it's probably normal for one of them. Oil usage will obviously vary on driving style as well, lots of short journeys and very harsh driving will mean it will use more; long journeys, especially at main road/motorway speeds, which are very undemanding on the engine, will cause it to use less.

Glen_Quagmire

captainspeed wrote:

Yes, I would definitely get the oil leak fixed, it's not expensive to do and hot oil could set the car on fire if it touches for example the catalytic converters!

captainspeed wrote:

Being tight with maintenance on a BMW is not a good idea, it will cost you more money in the long run and they do not take kindly to skimping on maintenance.

captainspeed wrote:

Regarding the oil use well if it's leaking that will definitely affect it for sure. I don't know a lot about the N52 engine yours has because mine uses the older M54 engine. However, the M54 is notorious for oil use because of the low tension piston rings and they normally start to use quite a bit after 100,000 miles. It's considered 'normal' for that engine to use up to a litre of oil every 600 miles. Make sure you're using LL01 spec fully synthetic from a good quality brand. In the M54 engined cars changing from 5W30 to 5W40 will cut it down a bit but it will still use some. Yours isn't the first N52 I've heard of that uses oil so I'd say it's probably normal for one of them. Oil usage will obviously vary on driving style as well, lots of short journeys and very harsh driving will mean it will use more; long journeys, especially at main road/motorway speeds, which are very undemanding on the engine, will cause it to use less.

Thanks for the detailed post.

Silly question - how does a mechanic identify where the leak is coming from as it could be coming from multiple locations? Is it just a case of shining a light in and seeing or do they have more advanced technical ways?

As you can tell I may aswel be looking into a hedge when looking at engines

H3llR4iser

If you have a trusted mechanic, just get him to check the car out before you go into scenarios and possible solutions - there might be a leak, but it might also be that a spill/leak was present in the past and you're simply smelling the leftovers.

I had some power steering fluid leak out of the reservoir on my car about 4 years ago ("spray" would be a more correct term - it went more or less everywhere in the engine bay) and no matter how much I had the engine cleaned, after a long drive you can still smell a bit of it if you open the bonnet. It made me paranoid for a long time - I was in the garage almost once a month to get them to check if there was another leak in the power steering loop, which there hasn't been since that first repair.


****PERSONAL QUIRK WARNING****

As it's a petrol BMW, I assume the engine block to be made of aluminium? My experience of aluminium blocks is mostly with Alfa Romeos, but I always thought they do generate a peculiar smell when hot. For example, my current 159 has an aluminium block and does smell a bit like the 75, while the 155 and 156 I had, with cast iron blocks, didn't have that "hot metal" smell. Again, might just be my nose/brain being weird

Glen_Quagmire

So I brought it to a mechanic to get the starter motor replaced. He said there is evidence of an oil leak there was a lot of oil in some of the trays he had to remove to get at the starter.

To your point, this could have been an old leak as I haven't had to top up oil by much since I bought the car, a couple of litres in about 4000 miles.

The mechanic said the engine would most like need to come out to find where the leak is (if there is one)

Don't know what to do

H3llR4iser

Glen_Quagmire wrote: »

So I brought it to a mechanic to get the starter motor replaced. He said there is evidence of an oil leak there was a lot of oil in some of the trays he had to remove to get at the starter.

To your point, this could have been an old leak as I haven't had to top up oil by much since I bought the car, a couple of litres in about 4000 miles.

The mechanic said the engine would most like need to come out to find where the leak is (if there is one)

Don't know what to do

As I said, I've never owned a BMW so I'm not familiar with the specific engine - some of the BMW drivers here will be more qualified to tell you if 2 liters over 6000km are excessive consumption and the sign of a leak.

My current 159 (1.9 petrol) uses no oil whatsoever at about 140.000 Km, but when I had Twin Spark engines they required pretty much regular topping up.

An idea could be to go to a detailer and get the engine bay cleaned properly - at that point, keeping an eye on it (and the ground beneath the engine where you park the car overnight) could shed some light onto the situation.

mikeecho

What's wrong with hot engine smell.. If only they'd make a magic tree in that scent

commited

Glen_Quagmire wrote: »

The mechanic said the engine would most like need to come out to find where the leak is (if there is one)

Get a new mechanic, that sounds like absolute nonsense.

Leonard Hofstadter

commited wrote: »

Get a new mechanic, that sounds like absolute nonsense.

Couldn't agree more with the above. BMWs do a few strange things compared to other makes but it's perfectly normal for one. For example, in cars M54 engines if you do a lot of short trips, you will see a lot of smoke out of the exhaust and you will see a lot of yellow stuff in the oil filler cap. It's just steam build up, a good motorway blast will cure it. But it looks like head gasket failure to the untrained eye (for the record, that engine never has a problem with the head gasket unless you've driven it for quite some time with the temperature gauge in the red).

The OP needs someone who is familiar with them and knows their apparent quirks.

Petrol BMWs only leak oil through the rocker cover gasket or the oil filter housing gasket (or the vacuum pipe in certain four cylinder engines). It would be very unusual for them to leak anywhere else.

Voodoomelon

Funny I always got the faintest whiff of coolant from my M52 after it had been running for a while, and it never leaked a drop. I remember the plastic engine cover being roasting too, you couldn't touch it. Never gave a moments trouble that engine.