QuestionQUESTION: I have a few queries relating to servicing my 1998 Accent.
In the service manual it mentions that I should 'replace' coolant, power sterring fluid,
gearbox oil, transmission fluid, and brake fluids at certain intervals.
What do they mean by replace. Should I 'flush out' or try and pump some of it out first or just 'top up'?
Which oils/fluids should I flush/pump or just replace? Would it be detrimental or a waste to flush out certain oils/fluids?
Should I purchase liquids that supposedly assist with my flushing out process?
I appreciate your help.
ANSWER: Replace typically means drain and refill.
For the coolant, remove the radiator cap, loosen the radiator petcock, and let the coolant drain into a container. Then reinstall the petcock and refill and bleed the cooling system appropriately.
For the power steering fluid, you'll need to suck the fluid out of the reservoir and put new in.
For the transmission, remove the drain plug and refill. For manual, this refill will be through a bolt hole in the front of the transmission. For the automatic, it'll be through the dipstick tube.
The easiest way to replace brake fluid is to suck the fluid out of the reservoir, add new fluid, and then crack the bleeders open and let gravity drain the old fluid out while you keep the level full with new fluid.
Flushing the fluids won't be detrimental, but is typically more than was intended by the maintenance schedule. It does, however, have the benefit that you're replacing more of the old fluid. The method above for the brake fluid manual transmission should replace nearly all of those fluids.
While I don't have your owner's manual to look at, I don't recall Hyundai ever recommending replacing the power steering fluid, and if I recall correctly, replacing brake fluid hasn't been recommended by Hyundai since about 1989.
Any liquids you purchase will not assist with flushing. They may have some desireable properties, but if you're using the proper fluids, these fluids should already have the correct additives in them. If you have an automatic transmission, absolutely do not put anything other than SPIII automatic transmission fluid in it.
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QUESTION: Why is the brake and power steering fluids not recommended to replace? Would it be detrimental to do so?
AnswerHyundai (or any other manufacturer) normally doesn't release the reasons why certain things are and are not on their maintenance schedule.
For the power steering fluid, it would be my speculation that the only contamination should occur from pump and rack wear, so contamination should be a minimum. Furthermore, the fluid is used solely for it's lubricative and hydraulic purposes, which are retained over a very long period of time. Compare this to an automatic transmission, for example, which uses similar fluid but has clutches that will wear with normal use, causing additional contamination. In addition, the transmission also relies on the friction properties of the fluid, which can deteriorate at a much quicker rate.
The issue with brake fluid is that it's hydroscopic, meaning that it will absorb water. Over time, the absorption of water can lead to rusting wheel cylinders and caliper pistions, and can also reduce the boiling point of the fluid. There's debate in the automotive repair industry as to whether anything of significance is gained by replacing brake fluid. I can say I've never done this in any of my cars and have never noticed a decrease in braking ability over the life of the car, but I have had to replace a couple wheel cylinders because they were leaking. In my opinion, these type failures are often unrelated to brake fluid contamination and occur with a low enough frequency that there's no economic advantage to regularly replacing the brake fluid. On the other hand, some manufacturers, such as Subaru, do require brake fluid replacement as regular maintenance.
