BMW 2/3/4/5 series from 2015 to 2019 - BMW B48 2.0 petrol coolant vent tube failures

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Fri 28 Apr 2023 18:25
BMW 2/3/4/5 series from 2015 to 2019 - BMW B48 2.0 petrol coolant vent tube failures - craig-pd130

If any owners of a BMW 2, 3, 4 or 5-series with the B48 2.0 litre petrol turbo engine (320i, 328i, 420i, 428i etc) are experiencing coolant loss, I strongly recommend they read this thread: f30.bimmerpost.com/forums/showthread.php?t=1889354

The plastic 'coolant vent tube' which connects between the cylinder head and the coolant expansion tank is failing in significant numbers, so much so that it's a free 'service call' in the US market, with a BMW US technical service bulletin describing it.

The tube is a hard plastic which becomes brittle from repeated engine heat-cycles and cracks (causing minor coolant weeps / loss) and eventually breaking completely (causing major unexpected coolant loss.

The vent tube on my son's 420i has just failed (broken off at the cylinder head), after 4.5 years and 47,000 miles, causing major coolant loss. Luckily he was only a few miles away and so was able to nurse it home without any overheating warnings.

However, despite the BMW US technical service bulletin, BMW UK claim not to have heard of the issue, deny seeing any such failures on cars over here, and are not interested in offering any goodwill.

I would recommend anyone with a BMW described above (also detailed in the BMW US technical service bulletin) gets the tube replaced as preventative maintenance. The part is £35 and readily available from BMW dealers.

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Fri 28 Apr 2023 19:04
BMW 2/3/4/5 series from 2015 to 2019 - BMW B48 2.0 petrol coolant vent tube failures - sammy1

"""Worrying that such a small part can potentially destroy an expensive engine. Typical that the UK customers will probably have to suck up the expense themselves.

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Fri 28 Apr 2023 19:04
BMW 2/3/4/5 series from 2015 to 2019 - BMW B48 2.0 petrol coolant vent tube failures - elekie&a/c doctor
Sounds like the similar problem with the Ford eco boost de-gas pipe . Unable to withstand the heating / cooling cycle.
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Fri 28 Apr 2023 20:06
BMW 2/3/4/5 series from 2015 to 2019 - BMW B48 2.0 petrol coolant vent tube failures - craig-pd130
Sounds like the similar problem with the Ford eco boost de-gas pipe . Unable to withstand the heating / cooling cycle.

Exactly that.

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Thu 18 May 2023 16:28
BMW 2/3/4/5 series from 2015 to 2019 - BMW B48 2.0 petrol coolant vent tube failures - craig-pd130

A quick update on this - we bought the replacement tube ourselves and had my local trusted mechanic fit it, together with a coolant flush and refill. Engine is fine and appears to have suffered no ill effects from losing a third of its coolant.

I spent half an hour on the phone with BMW UK, they still claim to be totally unaware of the issue, and furthermore claim that "technical service bulletins issued in the US don't necessarily apply here." Yet the replacement tube is a different part number to the one removed from the car. Funny, that.

If any owner of a BMW with the B48 motor is experiencing a slight coolant loss, get this tube replaced ASAP. The tube typically cracks and weeps a little before breaking completely. If it broke at speed on a motorway, the rapid coolant loss could wreck the engine.

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Thu 18 May 2023 21:57
BMW 2/3/4/5 series from 2015 to 2019 - BMW B48 2.0 petrol coolant vent tube failures - John F

If it broke at speed on a motorway, the rapid coolant loss could wreck the engine.

Don't BMWs have a low level coolant sensor which illuminates a hard to miss warning light on the dashboard? Even my 43yr old TR7 has one! Additional advice might be to always carry a 5l can of water for emergencies!

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Thu 18 May 2023 22:56
BMW 2/3/4/5 series from 2015 to 2019 - BMW B48 2.0 petrol coolant vent tube failures - bathtub tom
Don't BMWs have a low level coolant sensor which illuminates a hard to miss warning light on the dashboard? Even my 43yr old TR7 has one! Additional advice might be to always carry a 5l can of water for emergencies!

Come on , get real. Most drivers will completely ignore warning lights, thinking it'll be dealt with at the next service - if they ever go there!

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Sat 20 May 2023 16:13
BMW 2/3/4/5 series from 2015 to 2019 - BMW B48 2.0 petrol coolant vent tube failures - craig-pd130

Don't BMWs have a low level coolant sensor which illuminates a hard to miss warning light on the dashboard? Even my 43yr old TR7 has one! Additional advice might be to always carry a 5l can of water for emergencies!

It pops up a low coolant alert in the infotainment screen together with a warning light, but at motorway speeds the coolant loss could be big enough to allow the motor to overheat very quickly, before the driver can safely pull over.

Interestingly, what most people assume is a coolant temp gauge in BMWs is actually an oil temp gauge.

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Sat 20 May 2023 00:14
BMW 2/3/4/5 series from 2015 to 2019 - BMW B48 2.0 petrol coolant vent tube failures - edlithgow
According to a British mechanic who runs a car sourcing business here, German cars are especially vulnerable to plastics failure (both trim and componentry) in Taiwanese conditions. He ascribes this to them using/having to use more ‘environmentally friendly’ biodegradable materials
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Sat 20 May 2023 08:59
BMW 2/3/4/5 series from 2015 to 2019 - BMW B48 2.0 petrol coolant vent tube failures - daveyjp
Brittle engine plastics after 5 years is a feature of any German marque. No doubt they all use the same supply chain manufacturers.
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Sun 21 May 2023 04:42
BMW 2/3/4/5 series from 2015 to 2019 - BMW B48 2.0 petrol coolant vent tube failures - edlithgow
I think the implication was that it was mandated by German environmental regulation, though I dunno if this is true, since I’d expect such rules to be Europe-wide
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Sun 21 May 2023 13:37
BMW 2/3/4/5 series from 2015 to 2019 - BMW B48 2.0 petrol coolant vent tube failures - Brit_in_Germany

It could be that they are trying to use recyclable plastics rather than higher specification engineering ones such as glass-filled nylon.

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