COOLANT ISSUE - 2023 M4 Comp - advice needed!
Discussion
Hi all, new to this forum so apologies if I get anything wrong!
I bought an M4 Comp M Convertible new in Oct 2022, running in service seemed fine, then the car was serviced again in Oct 23. Jan 24 threw up multiple errors, recovered by Park Lane BMW and after investigation they discovered that the local dealers (Exeter) had overfilled the diff oil by 1/2 a litre. Obviously concerns that this could have caused excessive pressure, and had been running like this since either running in service or service in 23. BMW extended the warranty by an additional year until 2026 to give me peace of mind as they couldn't confirm damage hadn't been done to the vehicle.
Car serviced again by local dealer 300 miles ago (end of June 24), visual report shows coolant with a green circle, which apparently means all fine. They can't confirm whether they checked the consistency of the coolant only, or the levels (!) - but have gone off to find out.
Roll forward to last Friday, car had been absolutely fine, suddenly coolant light comes on. Straight to dealer, service person called later that day to say they thought it was an airlock. Watched video sent by technician, clearly shows reservoir as absolutely empty. Dealer happy to just give keys back having topped up coolant, but I refused to take car back until they can advise why there was either an airlock or the coolant was low enough to cause warning light to come on. They said they pressure tested and can't see any leaks, visually checked oil around cap (!) and it doesn't look like there's coolant in the oil.
Asked how much coolant was put in, told 1/2 a litre. I've read that coolant loss should be max 0.25% every 4-6 months, so on a 21 month old car max would be 1-2 percent - not 1/2 a litre. Local dealer now calling regional technical expert as they 'don't have a crib sheet telling them what to do next'.
Coolant is lifetime apparently, and shouldn't need anything doing to it at all.
My mechanical knowledge isn't great, but I've read that over filled rear diff can put pressure on head gasket, and head gasket issues can cause coolant leaks as coolant can flow into to places it shouldn't.
I wondered if any of the far more mechanically minded people on here would be able to give any advice? My concern is that the overfilled rear diff (and several thousand miles with it overfilled) has caused issues that are now starting to show.
I am now seriously considering rejecting the vehicle - I absolutely love it, but there's a chance the diff oil was overfilled at 1200 miles and so the car may well have spent the first 16 months of its life with an overpressurised engine, which from what I understand may cause ongoing problems - and while the 4 year warranty is good, the original intention was possibly to keep it for longer than that - and as we know, once the warranty has expired, it could be £££ in repairs if it's head gasket etc.
Please help - advice needed!
I bought an M4 Comp M Convertible new in Oct 2022, running in service seemed fine, then the car was serviced again in Oct 23. Jan 24 threw up multiple errors, recovered by Park Lane BMW and after investigation they discovered that the local dealers (Exeter) had overfilled the diff oil by 1/2 a litre. Obviously concerns that this could have caused excessive pressure, and had been running like this since either running in service or service in 23. BMW extended the warranty by an additional year until 2026 to give me peace of mind as they couldn't confirm damage hadn't been done to the vehicle.
Car serviced again by local dealer 300 miles ago (end of June 24), visual report shows coolant with a green circle, which apparently means all fine. They can't confirm whether they checked the consistency of the coolant only, or the levels (!) - but have gone off to find out.
Roll forward to last Friday, car had been absolutely fine, suddenly coolant light comes on. Straight to dealer, service person called later that day to say they thought it was an airlock. Watched video sent by technician, clearly shows reservoir as absolutely empty. Dealer happy to just give keys back having topped up coolant, but I refused to take car back until they can advise why there was either an airlock or the coolant was low enough to cause warning light to come on. They said they pressure tested and can't see any leaks, visually checked oil around cap (!) and it doesn't look like there's coolant in the oil.
Asked how much coolant was put in, told 1/2 a litre. I've read that coolant loss should be max 0.25% every 4-6 months, so on a 21 month old car max would be 1-2 percent - not 1/2 a litre. Local dealer now calling regional technical expert as they 'don't have a crib sheet telling them what to do next'.
Coolant is lifetime apparently, and shouldn't need anything doing to it at all.
My mechanical knowledge isn't great, but I've read that over filled rear diff can put pressure on head gasket, and head gasket issues can cause coolant leaks as coolant can flow into to places it shouldn't.
I wondered if any of the far more mechanically minded people on here would be able to give any advice? My concern is that the overfilled rear diff (and several thousand miles with it overfilled) has caused issues that are now starting to show.
I am now seriously considering rejecting the vehicle - I absolutely love it, but there's a chance the diff oil was overfilled at 1200 miles and so the car may well have spent the first 16 months of its life with an overpressurised engine, which from what I understand may cause ongoing problems - and while the 4 year warranty is good, the original intention was possibly to keep it for longer than that - and as we know, once the warranty has expired, it could be £££ in repairs if it's head gasket etc.
Please help - advice needed!
Doesn’t sound like great service form the dealers.
I am struggling to understand your statement:
“My mechanical knowledge isn't great, but I've read that over filled rear diff can put pressure on head gasket, and head gasket issues can cause coolant leaks as coolant can flow into to places it shouldn't.”
Head gasket and coolant loss is correct, but I fail to see how an overfilled diff would affect the head gasket.
I am struggling to understand your statement:
“My mechanical knowledge isn't great, but I've read that over filled rear diff can put pressure on head gasket, and head gasket issues can cause coolant leaks as coolant can flow into to places it shouldn't.”
Head gasket and coolant loss is correct, but I fail to see how an overfilled diff would affect the head gasket.
Truckosaurus said:
Can you even over fill a diff? Isn't 'filling it to the fill hole' what you do, and you physically can't get any more into it?
(Let alone it having no connection to the engine/coolant).
Or is there some funny front diff oil setup on 4wd BMWs?
You can overfill even with a fill hole if the car is jacked up in a certain direction, you'd have to really want it to do it though lol(Let alone it having no connection to the engine/coolant).
Or is there some funny front diff oil setup on 4wd BMWs?
I agree that I don't think an overfilled rear diff would have any effect on the engine at all, these are two separate issues mechanically.
The only connection I see is that the diff proves that Exeter BMW are incompetent at servicing your car, and so their incompetence is the most likely explanation for getting a coolant light 300 miles after they serviced it. E.g. they drained some coolant and forgot to refill it.
The car's probably fine tbh, and any issues are overwhelmingly likely to surface within the now-extended warranty.
I would suggest (a) find a better garage to service the car (b) worry less about it, it's probably fine, enjoy the car
Tash73 said:
Car serviced again by local dealer 300 miles ago (end of June 24), visual report shows coolant with a green circle, which apparently means all fine. They can't confirm whether they checked the consistency of the coolant only, or the levels (!) - but have gone off to find out.
They wouldn't check the consistency, just the level.Tash73 said:
Dealer happy to just give keys back having topped up coolant...
As pretty much any tech would...Tash73 said:
but I refused to take car back until they can advise why there was either an airlock or the coolant was low enough to cause warning light to come on. They said they pressure tested and can't see any leaks, visually checked oil around cap (!) and it doesn't look like there's coolant in the oil.
But actually they've done a proper job when presented with an unexpected loss of coolant.Tash73 said:
My mechanical knowledge isn't great, but I've read that over filled rear diff can put pressure on head gasket, and head gasket issues can cause coolant leaks as coolant can flow into to places it shouldn't.
Absolutely, categorically not true.Tash73 said:
I wondered if any of the far more mechanically minded people on here would be able to give any advice? My concern is that the overfilled rear diff (and several thousand miles with it overfilled) has caused issues that are now starting to show.
Let them sort the coolant issue, but you can't expect them to make it perfect at the first attempt - monitor the coolant levels now it's been topped up (take a picture of the coolant level every week).What they've done so far is absolutely normal - the techs aren't psychic, you've got to let them run through a set of diagnoses and monitor for issues. You can't always resolve things in 5 minutes of running the car up on the ramp or a test drive.
Edited by Krikkit on Wednesday 4th September 11:58
Tash73 said:
My mechanical knowledge isn't great, but I've read that over filled rear diff can put pressure on head gasket, and head gasket issues can cause coolant leaks as coolant can flow into to places it shouldn't.
I wondered if any of the far more mechanically minded people on here would be able to give any advice? My concern is that the overfilled rear diff (and several thousand miles with it overfilled) has caused issues that are now starting to show.
I am now seriously considering rejecting the vehicle - I absolutely love it, but there's a chance the diff oil was overfilled at 1200 miles and so the car may well have spent the first 16 months of its life with an overpressurised engine, which from what I understand may cause ongoing problems - and while the 4 year warranty is good, the original intention was possibly to keep it for longer than that - and as we know, once the warranty has expired, it could be £££ in repairs if it's head gasket etc.
Please help - advice needed!
The diff and coolant issues are not (cannot be) related.I wondered if any of the far more mechanically minded people on here would be able to give any advice? My concern is that the overfilled rear diff (and several thousand miles with it overfilled) has caused issues that are now starting to show.
I am now seriously considering rejecting the vehicle - I absolutely love it, but there's a chance the diff oil was overfilled at 1200 miles and so the car may well have spent the first 16 months of its life with an overpressurised engine, which from what I understand may cause ongoing problems - and while the 4 year warranty is good, the original intention was possibly to keep it for longer than that - and as we know, once the warranty has expired, it could be £££ in repairs if it's head gasket etc.
Please help - advice needed!
An overfilled diff will not impact the engine in any way so do not worry in that respect. Physically, the diff is completely separate from the engine (at the opposite end of the car) with its own oil, and simply cannot affect the pressures or anything else in the engine. Half a litre overfill won't have done the oil seals in the diff any good, and may have impacted lubrication in the diff if the oil had foamed due to being overfilled, but this is a stretch, IMO. To be honest it's pretty unlikely to cause any issues in reality.
Coolant is an interesting one. I had an M140i with the B58 engine (which the S58 in your car is very closely related to), and that used a very small amount of coolant from new. I had the car for 40,000 miles and had to top the coolant up twice. Speaking to a BMW dealer tech I know (a proper mechanic as well - ex REME), this is apparently normal, and is caused by the design of the water cooling set up on the turbo. In both cases the coolant level in the tank had simply dropped below the minimum mark rather than run completely dry and about 250-300ml was enough to take it comfortably back over the minimum mark (and fine again for another 15k or so)
Edited by Limpet on Wednesday 4th September 12:12
A diff is nothing to do with the engine and over filling it is very unlikely to do any damage, they normaly have some sort of vent system so they dont pressurize.
As to the coolant loss, 0.5l isnt that much, and it may well have been an airlock from new, although unusual,if its been pressure tested then it is most likely ok
.
As it was bmw who checked it and said its ok, then i would just drive it, keeping an eye on the coolant level every day or so, btw never open the coolant reservoir cap unless the engine is stone cold. When hot it may look like the level is low, so always check when cold and engine not running.
If there is a further problem then thats on bmw.
As to the coolant loss, 0.5l isnt that much, and it may well have been an airlock from new, although unusual,if its been pressure tested then it is most likely ok
.
As it was bmw who checked it and said its ok, then i would just drive it, keeping an eye on the coolant level every day or so, btw never open the coolant reservoir cap unless the engine is stone cold. When hot it may look like the level is low, so always check when cold and engine not running.
If there is a further problem then thats on bmw.
Problem 1 the diff
Diff is not connected in any way to the engine coolant system.
To the best of my knowledge (I am not a BMW expert) the diff on the M4 is air cooled.
The over filling, meh, not a big deal.
Unless it was pissing oil out that is!
Moving on...
Problem 2 the engine
Losing coolant should not happen on modern cars. It needs to go somewhere as the systems are sealed.
So it either left via an external leak or it left via an internal leak.
Unless the M4 is prone to airlocks from the factory (I doubt it) then its happened suddenly.
My concern would be that coolant is leaking internally.
Any excess steam from the exhaust at start up?
A good test can be a hydrocarbon test of the coolant. But no always 100%.
If that's -ve then the first thing I would be doing is taking the plugs out and scoping the engine looking for a clean piston....
Diff is not connected in any way to the engine coolant system.
To the best of my knowledge (I am not a BMW expert) the diff on the M4 is air cooled.
The over filling, meh, not a big deal.
Unless it was pissing oil out that is!
Moving on...
Problem 2 the engine
Losing coolant should not happen on modern cars. It needs to go somewhere as the systems are sealed.
So it either left via an external leak or it left via an internal leak.
Unless the M4 is prone to airlocks from the factory (I doubt it) then its happened suddenly.
My concern would be that coolant is leaking internally.
Any excess steam from the exhaust at start up?
A good test can be a hydrocarbon test of the coolant. But no always 100%.
If that's -ve then the first thing I would be doing is taking the plugs out and scoping the engine looking for a clean piston....
On what basis are you planning on "rejecting" the car given that you've had it for 2 years now?
There may be a coolant leak. That needs investigating. You may need to pay a diagnostic fee for doing so which would be refunded should any resulting work be required under the warranty your car still has.
But as for rejecting it, I think you've read too many internet articles and somehow made 2+2=5
There may be a coolant leak. That needs investigating. You may need to pay a diagnostic fee for doing so which would be refunded should any resulting work be required under the warranty your car still has.
But as for rejecting it, I think you've read too many internet articles and somehow made 2+2=5
Relax about the diff..........they all have a breather, if slightly over filled there'd be slightly less air space in the diff it'd probably build a little more air pressure but the breather will let that out?
https://www.youtube.com/watch?v=5cMtslWURrc
Re the coolant you could take it back and monitor the reservoir yourself daily/weekly etc to actually see if it's using it or if it's been a case of previously poor topping up etc. If it's losing any noticeable amounts then you need to go back to them?
https://www.youtube.com/watch?v=5cMtslWURrc
Re the coolant you could take it back and monitor the reservoir yourself daily/weekly etc to actually see if it's using it or if it's been a case of previously poor topping up etc. If it's losing any noticeable amounts then you need to go back to them?
Some info here, ranging from had it once and went away to more serious things, so monitor closely yourself would be my first step?
https://g80.bimmerpost.com/forums/showthread.php?t...
https://g80.bimmerpost.com/forums/showthread.php?t...
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