When to change coolant and brake fluid?

NewFolder

My car is due a service pretty soon, and I was wondering whether I should ask them to replace the coolant as well.

The coolant has not been changed since I purchased the car 3 years ago, and I have no idea when it was last changed before I had it (I have FSH, but most just say 'Full Service' plus any extras e.g. tyres so I don't know whether it was changed on any of these services). The coolant is the non-OAT type and is green in colour.

I've heard from a few places that coolant needs to be changed every so often as the water can separate from the coolant and cause corrosion, is this true? Or can coolant stay in the car for very long periods of time without issue, as some others have said?

I've drained a small amount of coolant out of the radiator and into a container to examine it, and it just looks like brand new coolant, although there are a few small black particles in it, if this is relevant?

Also, should I have the brake fluid changed as well? I've heard that water can get into it and reduce the braking performance over time. However, the garage says that they 'test' the brake fluid, so wouldn't they just replace it if it needed it?

Iceweasel

The colour of the coolant really tells us nothing as it can be dyed any colour the manufacturer chooses.

But generally the traditional type is blue or green and the OAT stuff is generally pinky-red.

If yours is non-OAT it should be changed every 3 years. - the OAT type is often called 'long-life' and is OK for 5 years.

It's the anti-corrosive qualities which lessen with time and often folks top up with neat water rather than the correct 50% mix, as they should.

Brake fluid does absorb moisture over time and that will lower the boiling point and thus could be catastrophic if you were descending long steep hills in the Alps or braking with a heavy trailer, for example.

Most manufacturers recommend changing the brake fluid after either 2 or 3 years.

I have to say I'm not much impressed with a workshop that just writes 'Full Service' - you should have a detailed list of exactly what they have done / adjusted / changed.

Retrogamer

On most modern cars, the coolant should have a lifespan of 5 years.
Most people make the mistake of seeing they still have a strong mixture, so it is still able to work against water freezing but it will become corrosive.

Brake fluid, most will last 2-3 years so if that's not been done yet it would be worth changing it now. I'm not aware of any way of testing the fluid for water moisture though.

flashg67

A decent garage should have a brake fluid tester that measures the boiling point of the brake fluid - in my day the lower limit was 150 deg C, but may be higher nowadays with modern cars.

Some coolant changes aren't specified until 10 years, but for the cost, it's not worth skimping on IMO

Joe_Horner

Retrogamer wrote: »

I'm not aware of any way of testing the fluid for water moisture though.

There are three basic methods are available.

One is to send a sample for lab analysis of its boiling point - quicker and cheaper to just replace it.

The next is to test it electrically, which is what most garage testers do. Electrical testing isn't as accurate as a boiling point test because the results depend on the original properties fo the fluid as well as the moisture content, and the original properties won't be known. It will generally "fail" fluid that's still ok rather than pass fluid that's saturated, hence occasional claims that it's little more than a money-making device for the garage.

The third way is with chemical test strips - a bit like litmus paper for reading pH. This is the least accuratebut it's quick, easy and cheap - dip a strip in the reservoir and see what colour it turns.

Water in the brake fluid won't affect brake performance in normal driving, btw. It lowers the boiling point but, unless you drive very aggressively or live in mountains, you shouldn't be getting anywhere near the boiling point anyway!

What it can do is cause corrosion inside cylinders, calipers and steel pipes over time, leading to them leaking or seizing. Fluid has corrosion inhibitors to prevent this but they become ineffective over time. Changing the fluid every couple of years is a relatively cheap insurance policy against bigger bills.

NewFolder

I think it's probably better to get them both changed in that case then.

One other thing, my alternator belt has recently started squeaking a bit. It's noticeable, but not loud, i.e. I can hear it if the radio is switched off, otherwise I can't. How long approximately will I have before this starts causing problems or gets really bad? Will it last approximately 800 miles until the service is due, bearing in mind it only started doing it about a week ago?

Strider590

I'm gonna throw a spanner in the works here, I don't believe that coolant mix really matters until winter months and freezing temps, in fact in some very cold countries they increase the coolant to water ratio and in years gone by it was recomended to change the mix for different seasons. It also doesn't take much coolant to increase the boiling temperature of water. Coolant also doesnt help to dissipate heat to the outside more efficiently, if it did we'd be using it in our homes central heating, same logic applies to the corrosion argument.
What it does do very well, is leave residue whenever there is a leak, this makes finding/fixing leaks so much easier.

Your going to end up replacing it when you have a cambelt and water pump change anyway (which is usually X miles or 4-6 years). If you don't have these changed, then you should be worrying about the belt snapping long before the coolant becomes an issue.

Brake fluid, I don't think anyone ever changes it, but it should be done according to the service schedule in your owners manual.

vikingaero

I'm going to talk colours! Pink coolant is far prettier and better!

OK I'll justify my statement. I look after a range of cars for my extended family from brand new cars to half a dozen cars around 10 years old. With the pink coolant it is easier to check the visual condition of the coolant and the level. With the blue/green coolant it gets harder to check if it isn't sunny and if the coolant bottle ages and goes opaque.

When we have had problems with a car any contamination of the pink coolant is instantly easy to spot - it loses the bright pink colour. With the blue/green coolant the colour can just slowly go darker.

Prothet_of_Doom

Brake fluid gradually takes on moisture, and whilst this is okay in most day to day situations, it means that hill descents are more risky.

So I'd be asking them to change the brake fluid. If they can do it with a vacumm fill system, I'd be most impressed, as I've lost count of the number of bleed nipples that I've snapped off.


On the subject of hill descents, it is better to do short periods of hard braking, followed by time to allow air flow to cool the pads, rather than keep foot on brake, and have no chance for airflow to cool the pads.

Retrogamer

Strider590 wrote: »

I'm gonna throw a spanner in the works here, I don't believe that coolant mix really matters until winter months and freezing temps, in fact in some very cold countries they increase the coolant to water ratio and in years gone by it was recomended to change the mix for different seasons. It also doesn't take much coolant to increase the boiling temperature of water. Coolant also doesnt help to dissipate heat to the outside more efficiently, if it did we'd be using it in our homes central heating, same logic applies to the corrosion argument.

When we got a new boiler installed, it had an anti corrosive liquid put in a the same time

When the coolant turns brown from rust in the header tank, that's a good indicator that the anti corrosive properties are no longer working and the engine is starting to rust on the inside. Radiator and water pump failure depending on the materials used happens a lot more rapidly on cars that haven't had their coolant replaced often enough

Strider590

Retrogamer wrote: »

Radiator and water pump failure depending on the materials used happens a lot more rapidly on cars that haven't had their coolant replaced often enough

I think the cambelt interval would be often enough, another reason perhaps to always do the water pump at the same time. Assuming the car has one of course....