We do a "big" supermarket shop roughly every two weeks. Mostly from Aldi but also get some favourites from Lidl - Filtered milk, peppered salami and sweet chilli rice crackers for starters. As there's "heavy" stuff to lug about - like milk etc - and with Mrs J's bad back I tag along to do the heavy lifting. Of course while she's going around with the trolley it leaves me free to take a good look at the "specials" and on this occasion I was unable to resist temptation! https://offers.kd2.org/en/gb/lidl/pkRQj/
It's a resistive type tool and they don't get a particularly good name for accuracy but they are very convenient to use. Only £7.00? Wonder if I can sneak it into the trolley without Mrs J noticing? Wa hey, it's in the shopping bag!
Ok, so what's this all about? Well, as many on here will know very well, conventional brake fluid is hygroscopic which means it absolutely loves water and absorbs it out of the air at any opportunity it gets. - So don't take the top off brake and, clutch fluid reservoirs unless topping up. Yes there's an air hole but you'll let much more air, and so moisture, in if you take the top off - This is unfortunate because temperatures in braking systems can easily exceed the boiling point of water and when water boils it becomes a gas and gasses are compressible! Brakes work because the brake fluid is not compressible so can transmit the movement of the brake pedal to the calipers/cylinders at the wheels. If there's enough water mixed with the fluid - and it doesn't take much - then when it boils and becomes a gas the brake pedal, with almost no prior warning, can go right to the floor and you'll find the brakes will not now slow the vehicle. For this reason most manufacturers recommend flushing through the braking system with fresh fluid every 2 to 3 years. This problem is a most insidious one as the brakes will operate normally until enough heat is generated - maybe by descending a long steep hill with lots of brake use or doing a couple of consecutive very hard stops from high speed perhaps on a motorway in heavy traffic. Of course water in the brake fluid will cause more rapid corrosion of caliper pistons etc too, so it would be very handy to know if your brake fluid has absorbed a potentially dangerous amount of water wouldn't it? Well you can.
There are currently two main types of tester one type actually applies heat to the fluid until it boils the other puts a small electrical current across a carefully calibrated distance between two electrodes and measures the electrical resistance of the fluid between them. The Lidl one I bought - see above - is of the resistive type and I bought it partly because, if it proves to be accurate, it's going to be very quick and easy to use whenever I'm working on one of the family cars. Trouble is there are some claims that this type is not very accurate but I've been looking into this and I think I know why.
There are different specs of brake fluid! Ok, the obvious one is silicon based fluid - DOT5 - which this tester won't work with at all - indeed you wouldn't want to use it with this type of fluid as it doesn't absorb water in the first place (it has other reasons why I wouldn't use it however) so we can forget about it. "Standard" brake fluids are given a DOT number. DOT3 spec used to be very popular in everyday cars but has now been largely superseded by DOT4 which has a higher boiling point. Some manufacturers - my wee Seat Ibiza being one - now recommend DOT4 PLUS (you'll find it labeled as "super" sometimes) which has a higher boiling point again. Then there's DOT5.1 which is yet higher again and mostly used in very high performance or heavy vehicles. By far the most common you'll encounter is DOT4.
Many years ago I decided to buy the boiling point type because of it's greater accuracy and that I was looking after the "family fleet" so could justify the considerably greater cost. I went for the one made by Liquid Levers, just over the water in Fife, and it's been an excellent purchase:
You connect the leads to the car battery and dunk the probe on the bottom of the tool into the brake fluid reservoir until the wee hole in it's side is submerged. Then you press the red button and the element in the probe boils the fluid whereupon a reading is displayed directly on the screen in degrees centigrade. You simply need to compare that reading to the scale on the chart (of which there's a "quick glance" version on the tool:
Calibration of the tool needs to have an eye kept on it but the process is very simple. All you do is to operate the probe in distilled water when you should see 100 C displayed. If it doesn't show this you return it for calibration. So far it's always checked out so I don't know what they would charge for calibration.
The resistive tool:
Takes a triple A battery and is operated by dunking it's probes:
into the fluid and pressing the red button on the handle:
whereupon a series of lights illuminate against the scale indicating the percentage of water in the sample.
Having only bought it this week I haven't actually tried it yet but it seems very simple to operate. My intention is to check with both the older "boiling point tool and the new resistive one and keep a record of results which I'll compare after I've done checks on several of the family cars. Then we'll be able to see how accurate and reliable the new tool is? Bearing in mind that the different specs of fluid exist I'm interested to see the new tool has DOT4 printed on it. I believe it probably won't be so accurate if used on DOT3 or DOT 5.1 and maybe a little less reliable on DOT4 plus? It's going to be interesting to see.
I think the reputation for erroneous/unreliable results which these resistive tools seem to have may be because people don't realize they are only accurate with one DOT spec of fluid - in this case DOT4. As long as it proves to work well on DOT4 that'll do me fine because everything in the family fleet runs DOT4 except the Ibiza - and even that actually has DOT4 in it just now because I recently found out that the garage that did the flush for me back in the spring keeps their pressure bleeder filled with DOT4! This really shouldn't cause any problems but I'll be flushing it through with DOT4 plus next time I service her.
Once I've compiled my results, if there's anything interesting to comment on, I'll come back to this thread with some comment. Don't hold your breath though, might take me a year to get enough results to be meaningful.
It's a resistive type tool and they don't get a particularly good name for accuracy but they are very convenient to use. Only £7.00? Wonder if I can sneak it into the trolley without Mrs J noticing? Wa hey, it's in the shopping bag!
Ok, so what's this all about? Well, as many on here will know very well, conventional brake fluid is hygroscopic which means it absolutely loves water and absorbs it out of the air at any opportunity it gets. - So don't take the top off brake and, clutch fluid reservoirs unless topping up. Yes there's an air hole but you'll let much more air, and so moisture, in if you take the top off - This is unfortunate because temperatures in braking systems can easily exceed the boiling point of water and when water boils it becomes a gas and gasses are compressible! Brakes work because the brake fluid is not compressible so can transmit the movement of the brake pedal to the calipers/cylinders at the wheels. If there's enough water mixed with the fluid - and it doesn't take much - then when it boils and becomes a gas the brake pedal, with almost no prior warning, can go right to the floor and you'll find the brakes will not now slow the vehicle. For this reason most manufacturers recommend flushing through the braking system with fresh fluid every 2 to 3 years. This problem is a most insidious one as the brakes will operate normally until enough heat is generated - maybe by descending a long steep hill with lots of brake use or doing a couple of consecutive very hard stops from high speed perhaps on a motorway in heavy traffic. Of course water in the brake fluid will cause more rapid corrosion of caliper pistons etc too, so it would be very handy to know if your brake fluid has absorbed a potentially dangerous amount of water wouldn't it? Well you can.
There are currently two main types of tester one type actually applies heat to the fluid until it boils the other puts a small electrical current across a carefully calibrated distance between two electrodes and measures the electrical resistance of the fluid between them. The Lidl one I bought - see above - is of the resistive type and I bought it partly because, if it proves to be accurate, it's going to be very quick and easy to use whenever I'm working on one of the family cars. Trouble is there are some claims that this type is not very accurate but I've been looking into this and I think I know why.
There are different specs of brake fluid! Ok, the obvious one is silicon based fluid - DOT5 - which this tester won't work with at all - indeed you wouldn't want to use it with this type of fluid as it doesn't absorb water in the first place (it has other reasons why I wouldn't use it however) so we can forget about it. "Standard" brake fluids are given a DOT number. DOT3 spec used to be very popular in everyday cars but has now been largely superseded by DOT4 which has a higher boiling point. Some manufacturers - my wee Seat Ibiza being one - now recommend DOT4 PLUS (you'll find it labeled as "super" sometimes) which has a higher boiling point again. Then there's DOT5.1 which is yet higher again and mostly used in very high performance or heavy vehicles. By far the most common you'll encounter is DOT4.
Many years ago I decided to buy the boiling point type because of it's greater accuracy and that I was looking after the "family fleet" so could justify the considerably greater cost. I went for the one made by Liquid Levers, just over the water in Fife, and it's been an excellent purchase:
You connect the leads to the car battery and dunk the probe on the bottom of the tool into the brake fluid reservoir until the wee hole in it's side is submerged. Then you press the red button and the element in the probe boils the fluid whereupon a reading is displayed directly on the screen in degrees centigrade. You simply need to compare that reading to the scale on the chart (of which there's a "quick glance" version on the tool:
Calibration of the tool needs to have an eye kept on it but the process is very simple. All you do is to operate the probe in distilled water when you should see 100 C displayed. If it doesn't show this you return it for calibration. So far it's always checked out so I don't know what they would charge for calibration.
The resistive tool:
Takes a triple A battery and is operated by dunking it's probes:
into the fluid and pressing the red button on the handle:
whereupon a series of lights illuminate against the scale indicating the percentage of water in the sample.
Having only bought it this week I haven't actually tried it yet but it seems very simple to operate. My intention is to check with both the older "boiling point tool and the new resistive one and keep a record of results which I'll compare after I've done checks on several of the family cars. Then we'll be able to see how accurate and reliable the new tool is? Bearing in mind that the different specs of fluid exist I'm interested to see the new tool has DOT4 printed on it. I believe it probably won't be so accurate if used on DOT3 or DOT 5.1 and maybe a little less reliable on DOT4 plus? It's going to be interesting to see.
I think the reputation for erroneous/unreliable results which these resistive tools seem to have may be because people don't realize they are only accurate with one DOT spec of fluid - in this case DOT4. As long as it proves to work well on DOT4 that'll do me fine because everything in the family fleet runs DOT4 except the Ibiza - and even that actually has DOT4 in it just now because I recently found out that the garage that did the flush for me back in the spring keeps their pressure bleeder filled with DOT4! This really shouldn't cause any problems but I'll be flushing it through with DOT4 plus next time I service her.
Once I've compiled my results, if there's anything interesting to comment on, I'll come back to this thread with some comment. Don't hold your breath though, might take me a year to get enough results to be meaningful.