Car Hire & coolant issue

[[TW]Fox]

Actually it is not completely sealed, there is a pressure relief in the system and some steam can escape, and if the tank had been overfilled at some stage it can often blow it out, you also assume that it was fully bled at the factory, not always the case and hire cars often have their first inspection skipped.

Under normal circumstances, the level does not need topping up. It really is that simple - cars do not require coolant topups as a matter of routine like they might need oil topups or similar. Perhaps after tens of thousands of miles, but not at the age of a typical rental car.

If a system is losing coolant, it's got a problem - whether its using it, leaking it our or venting it due to excess pressure.

Why the hell would you want to be messing about with that on a rental car?! It's not your problem, get it swapped.

It is not uncommon for them to need topping up after new before first service, depends on how new the car is.

It is uncommon.

Also water contracts when cold and not frozen.

Not by enough to trigger a low coolant warning alert.

This car has a fault - exchange it for another and get on with your life.

 

[Dr Who]

Under normal circumstances, the level does not need topping up. It really is that simple - cars do not require coolant topups as a matter of routine like they might need oil topups or similar. Perhaps after tens of thousands of miles, but not at the age of a typical rental car.

If a system is losing coolant, it's got a problem - whether its using it, leaking it our or venting it due to excess pressure.

Why the hell would you want to be messing about with that on a rental car?! It's not your problem, get it swapped.

It is uncommon.

Not by enough to trigger a low coolant warning alert.

This car has a fault - exchange it for another and get on with your life.

If it was almost at the sensor level and contracted slightly then yes enough to trip the sensor.

It is pretty simple, top it up and see if it loses any more.

And yes it is very common, I have seen it at least a dozen times over the years.

Just because you haven't doesn't mean it doesn't happen.

Car not fully bled, run for a few hundred miles and the air replaces the coolant in the header tank. Doesn't mean it is losing coolant.

Same as what happens after you drain and refill coolant.

Sure get it swapped, no skin off my nose.

 

[[TW]Fox]

If it was almost at the sensor level and contracted slightly then yes enough to trip the sensor.

And why would it be at almost the sensor level? Because it's lost some! And why would it have lost some... because it has an issue somewhere.

It is pretty simple, top it up and see if it loses any more.

This is the right thing to do if its your own car. However, it is absolutely not your duty to be messing about watching coolant levels on a car you are paying 20, 30 maybe 40 quid a day to hire!

Who knows where the coolant has gone? Perhaps it was just wrong in the first place. Perhaps there is a leak and it'll eventually overheat 300 miles from home. Why would you even want to think about it?!

And yes it is very common, I have seen it at least a dozen times over the years.

Then you've seen a lot of broken cars.

Car not fully bled, run for a few hundred miles and the air replaces the coolant in the header tank. Doesn't mean it is losing coolant.

How many sub 1 year old cars are 'not fully bled'?!

 

[Malt_Vinegar]

My 750i pinged up with low coolant the other day. Turns out it was a bad o-ring on the lower hose coolant temp sensor. It would drop a small amount of coolant when it was cooling down and also warming up.
It cost me an extortionate £1.80 to fix it, genuine BMW parts only from the main dealer (of course) mrk..
They even mailed it to me for free!

However, as Fox said, if a car is using coolant it's broken in some way..

 

[Dr Who]

However, as Fox said, if a car is using coolant it's broken in some way..

Correct, I am disputing that it has definitely used coolant.

2 main things impact a new car coolant level.

1. Not bled fully at the factory, usually corrected and check at first free inspection, but cooling systems will self bleed and that air in the system swaps place with water in the header tank. Just needs a top up after a few hundred miles.

2. Hose expansion. As the new car settles some of the hose will seat and stretch and not return to original size. not much of an impact but will lower the coolant level slightly

Clearly Fox is not as fluent mechanically as he is with BMW specs, but hey ho, for the sake of peace, the car is broken, get it swapped immediately before it strands you.

 

[[TW]Fox]

Neither of those things are exactly common on a new car and other than specialist performance cars few if any new cars get a 'first free inspection' post sale.

However even if we concede there is a slight possibility of one of those two things you've suggested being true you are still missing the point - the point is that why would you even want to entertain thinking about what might be wrong? The most likely explanation is that the car is faulty - you are paying £££ per day to rent it, why on earth would you take working out whether its broken, watching the level, blah blah?

Frankly you'd swap a rental car if it asked for an oil topup and that *IS* something thats normal. The idea of not doing so with one displaying coolant level warnings is nonsensical.

 

[acemastr]

Correct. It is a sealed system - the car doesn't use coolant in its normal operation so there is no need to top up a brand new or even reasonably new car with coolant unless there is a fault in the system which has caused the level to drop from max to below minimum. An inch below is an inch below, if that was the correct level it wouldn't have a minimum mark an inch higher would it?

The coolant has gone somewhere and it's not the OP's problem where that is. The car has a problem with the cooling system.

New cars are delivered to dealers with minimal fluids, 'transport' amounts. My Subaru wasn't topped up correctly by the dealer prior to selling to me so I imagine this hire car hasn't actually used any, it simply wasn't topped up to the correct level by the dealership prior to giving it to the rental company. There's probably a perfectly fine amount for it to run and not have a problem, it's just the OP actually bothered to look.

 

[[TW]Fox]

it simply wasn't topped up to the correct level by the dealership prior to giving it to the rental company.

And yet the car was fine for months before randomly triggering the warning light only now...

 

[acemastr]

Cold weather, heater matrix being used to warm cabin... clutching at straws here

 

[[TW]Fox]

It's almost as if the best idea is to just make it the hire firms problem and get on with your life in a car without warning lights showing on the dash

 

[Clarkey]

It already is the hire firms problem, they said to top it up with some water, he did that. I really don't understand why anyone would give this even a moment more thought.

 

[Dr Who]

Cold weather, heater matrix being used to warm cabin... clutching at straws here

This is pretty accurate surprisingly. The heater matrix wont receive much water flow during the summer months, so once it get's cold, the increased flow can cause the air bubbles that might have been trapped to re-enter the system and end up in the header tank.

The cars are usually shipped on minimum water level, so it doesn't take much change to drop the coolant below and then you get your warning light.

Like I say, it is reasonably common on new cars, a quick google search will prove that.