Coolant leak at side of the road

[Dr. Zed]

So last weekend I replaced both the belts, the thermostat and the water pump. Flushed the coolant out too. All seemed good but then today I was stood in traffic and it started overheating. Pulled over and there's coolant all over the place (typing this sat at the side of the road waiting for recovery).

I've had a look but I can't see where it's coming from. So my question is, is there any obvious/weak points I should look for?

It appears to be coming from the passenger side. The coolant and thermostat both appear dry, as are the belts. Reservoir perhaps as it might explain why it lost that much coolant that quickly.

Any help appreciated as I have 2 hours to wait for RAC.

 

[bigwinn]

Expansion tank mate

 

[bigwinn]

Look for small cracks in it

 

[N4LLY]

That's a bummer

 

[Dr. Zed]

Expansion tank mate

That was my first thought too but I've just thrown some water into it from a bottle of water I have in the car and it's not leaking. Unless it's higher up along the side walls. Is it relatively easy to replace?

 

[Dr. Zed]

If it helps, the coolant is all over my passenger front wheel. Somehow it got through the arch lining.
Just in case that's evidence of something in particular.
Thought maybe the pump if it was throwing coolant everywhere but that's dry and on the wrong side of where the coolant is on the road ...

 

[bigwinn]

I’m still saying expansion tank that side

You may miss the hole as they can be small or hidden

 

[Dr. Zed]

I’m still saying expansion tank that side

You may miss the hole as they can be small or hidden

You might be right. At least expansion tank is relatively easy to fix.
Should have done it when I did the rest. Idiot. What are the chances that would go after doing the pump and thermostat though!

 

[bigwinn]

When we did johns system next door the newer pump seemed to put more pressure in the system and popped the tank

Since we fitted a new tank it’s been fine and he is currently gallivanting around the uk in his z

 

[enuff_zed]

Another vote for expansion tank. Hairline cracks open up under heat and pressure then close again.
Mind you, mine was the o-ring seal at the bottom where it sits into the cradle.

Just checking: not an auto is it? If so you'll need to get a new oil cooler thermostat too. It sits in the bottom of the tank and the BFF spring inside blows it apart when you remove the tank. Mine shot past my ear!

 

[Dr. Zed]

When we did johns system next door the newer pump seemed to put more pressure in the system and popped the tank

Since we fitted a new tank it’s been fine and he is currently gallivanting around the uk in his z

Should have done it when I did the rest. I'll need to get more coolant and probably do another flush as I don't trust the stuff that RAC put in it.

Seems the new pump might be the culprit. Ironically.

 

[Dr. Zed]

Another vote for expansion tank. Hairline cracks open up under heat and pressure then close again.
Mind you, mine was the o-ring seal at the bottom where it sits into the cradle.

Just checking: not an auto is it? If so you'll need to get a new oil cooler thermostat too. It sits in the bottom of the tank and the BFF spring inside blows it apart when you remove the tank. Mine shot past my ear!

I'll get it off the ground tomorrow but expansion tank seems to be the likely issues

It's a manual, thankfully

 

[Dr. Zed]

Speaking of coolant stuff. I did a flush last time by cycling through water and coolant. The issue is that after doing the flush of water there's still water left when I put the coolant in there. Since it's ready mixed this would dilute it even more. Is there anyway to ensure I get most of the water out or is it literally just a case of doing a few flushed with coolant after the initial water flush?

 

[Sidewaze Samm]

What are the chances that would go after doing the pump and thermostat though!

Having not checked the coolant level for 12 months, I checked it the day before going on a 600-mile bank holiday roadtrip. The cap was very tight to get off but level was fine. Later in the day - coolant everywhere but where it should be and weekend plans for the zed abandoned!
What are the chances that would go after merely checking the level...?

 

[Chris_D]

Here's a tip I heard from more than one BMW mechanic - never fill your coolant tank to full!
Just keep it at the lowest indicated level possible, especially in summer.
You'll thank me later.

 

[Dr. Zed]

Here's a tip I heard from more than one BMW mechanic - never fill your coolant tank to full!
Just keep it at the lowest indicated level possible, especially in summer.
You'll thank me later.

Well I assume without anything resembling an overflow tank, any coolant passed max is just going to result in over expansion of the tank. But the level was definitely not more than the max at cold, that's for sure

 

[Chris_D]

Here's a tip I heard from more than one BMW mechanic - never fill your coolant tank to full!
Just keep it at the lowest indicated level possible, especially in summer.
You'll thank me later.

Well I assume without anything resembling an overflow tank, any coolant passed max is just going to result in over expansion of the tank. But the level was definitely not more than the max at cold, that's for sure

No I think the point is that the expansion tank is too small to compensate for expansion when running hot if the reservoir is kept topped up to max. Hence if you keep it at the lowest indicated level there is more room in the system for expansion.
There is a relief valve / vent for over-expansion but it’s obviously not effective enough to prevent the expansion tank from splitting when hot.