==> | Part 1: Overview; tires/brakes |
Part 2: Underhood | |
Part 3: Headlights: the Big Schnoz | |
Part 4: Inverter pump | |
Part 5: Coolant testing | |
Part 5b: Engine coolant | |
Part 6: Transaxle / driveline, references |
Some of the rotation intervals were a bit longer than they should have been, to put it charitably. Somewhere around 76K I did one and immediately noticed a loud "wooba-wooba-wooba" sound coming from somewhere around the right side of the car while driving, peaking around 18 MPH when whatever was making the noise struck resonance with the suspension parts and/or body. Closer inspection and feeling along the inner part of the tread revealed that the tread blocks were becoming a little bit feathered -- where more wear was happening at one edge of each block than the other, leading to slight height mismatches between adjacent tread-block boundaries and a generally not-perfectly-round tread surface. The most noticeable wear appeared to be on the inner half of what used to be the rear tire, and the feathering direction strongly suggested that the right-rear hub was toed-in just a little too much and making its tire "crab" ever so slightly sideways down the road. This affected the inner part of the tread because the rear wheels have some negative camber [e.g. tilted inward] relative to the front wheels which are pretty much dead-vertical and thus the rears are taking most of their load on the inner half of the tread. Swapping wheels into a different camber situations suddenly brought out the effects of the feathering much more strongly. | |
Toyota claims that anything involving the rear axle cannot be aligned, the
entire rear axle has to be replaced to correct any problems there.
That's total bunkum. At somewhere around 90,000 miles I managed to realign the rear hub, using some shims generously provided by Bob Wilson from a kit of same he had purchased. Unfortunately I didn't get any pictures of this procedure but basically it involved finding a long straight board, laying it carefully against the tire sidewall and seeing how that matched up with the rocker panel of the rest of the car. Without the shims it definitely showed that the wheel was pointing somewhere toward the right-hand headlight, i.e. not straight; once the correct shims were slipped in behind the front two bolts for the hub mounting plate and everything tightened back down, the board lay exactly parallel with the car and I declared the problem fixed. But it's taken 20,000 miles and another couple of front/back swaps to very slowly start working the effects of the misalignment back out of the tires now that they track straight. I deliberately decided to put up with the noise as an experiment, and also realized that it would take me much longer than most owners to get the alignment fix to "settle in" since I run these tires at fairly high pressures and thus see less tread wear per mile than many other installations. I don't mind a little tire noise, really -- one gets a certain amount of that anyway when running at 55 - 60 PSI in these things, and the MPG advantages and better braking and cornering far outweigh any conceptual yacht-like "luxury" feel that is the only argument in favor of running lower pressure. This, in fact, is the ONLY alignment work the car has gotten since the check done before I took delivery in early 2005. Still tracks as true as the day I drove it home. And given some of the bumps it's been over, I'm often astounded that the thing has a front end left at all, let alone still in proper alignment. It's one tough little nut. Notably, all the struts seem to still be in fine shape as well -- no leaks or other issues, car still handles fine and doesn't bounce, etc. I expect to have to replace some of them sometime down the road, and when I do there are some excellent writeups in the reference section on strut replacement and suspension mods by other community members. Maybe some future "150K maintenance" writeup will include some suspension work, but at this juncture I'm probably a bit underequipped to tackle that sort of thing. |
(Toward front of car) | |
Left pair, 6K on the tires | Right pair, 6K |
Left pair, ~ 70K on the tires |
Right pair, 70K
*Note: rear is no longer a Hydroedge! |
This pretty clearly shows the Hydroedge treadwear changes to date.
There were some interim sets of comparison pictures, but looking at the
current endpoints -- a fairly early state versus the present 110+K -- is
more instructive in terms of seeing overall tread wear rate. Here we see
wear that is pretty much dead-flat across the entire tread on all of them,
as opposed to the
edge wear
we easily see from running at the door-placard pressure, and while I've
pulled the occasional fun lateral Gs around the mountain-road bends I'm
generally pretty gentle on tires so the overall wear is fairly low. But
after 70K on this set there's definitely less rubber on the treads than they
began with.
About a thousand miles before the second set of pix, the right-rear Hydroedge was lost after probably backing over something sharp on one of the 2009 summer road trips and sustaining a puncture that was declared too close to the sidewall to patch. So I wound up with one oddball cheap POS Korean tire just to get me back on the road, which astoundingly enough doesn't cause any handling problems so rather than replace any more perfectly good remaining tires I'll just run with the odd one, hopefully for the remainder of the Hydroedges' useful life. It's a larger circumference than the Hydroedges, screwing up my differential-speed TPMS something awful, but I'll live with that for now and just learn a new pattern in the green diamond. The cumulative wear on the right-side front Hydroedge can still be seen, and none of them are down anywhere near the wear-indicator bumps yet. They're supposedly a 90K life rated tire anyway. |
All brakes are taken apart, eyeballed, and cleaned per the procedures outlined
in the 50K brake check page. The slide
pins for the front calipers are still quite clean here, although at this point
needing a bit more grease applied before reassembly. It's important to keep
them moving freely so that calipers don't wind up frozen in place and pushing
only from one side or the other which would really stress the wheel bearings.
In general it's good to just remove a car's wheels once in a while and make sure it can still be done by the owner, especially if it's been anywhere near a garage where they even waved an impact wrench toward the lugnuts let alone applied it. It's an opportunity to clean off the backside of the rim, wipe rust away from hub parts, make sure the rotors or drums can still come off easily, and check the lug nuts and studs. I keep a light layer of anti-seize on the lug threads, ignoring the fervent and quite unfounded cries of those who insist they must go on dead-dry. They can go pound sand. *I* know the value of thread lube and what about 78 foot-pounds of torque feels like through the cross-wrench in my hands *and* I can always get my wheels off myself. |
More importantly, the ORIGINAL pads here have substantial thickness left, at 110K on the clock. We can Visually compare them at 50K and now, since I haven't bothered taking quantitative measurements at any of these inspections. Now they're a little further down, but nowhere near what most vehicles would show by now. Here is the best possible testament for A> regenerative braking that stays off the hydraulics until absolutely necessary and B> proper use thereof. These are likely good for another 100K, unless they succumb to plain old corrosion in the interim. With periodic cleaning and lubrication of various contact surfaces, that shouldn't get to be a problem either. |
Same with the rear shoes -- lots of liner left, no worries here. Minor cleanout and re-greasing of the backing-plate sliding points is done to discourage rust and make sure everything moves freely. |
On a slightly different tangent ... after 5 years, what state is the brake fluid in? Many people would expect it to be way overdue for a flush/replacement. There are numerous articles and posts floating around on brake fluid and its affinity for water and how the more water content it collects, the more likely it is to corrode internal brake system parts and boil into vapor under severe heating and cause spongy braking. The forums are full of self-styled "experts" telling each other that no brake fluid can possibly be any good after two or three years, and when the ambient babble gets loud enough one might be tempted to start believing it. |
Not so fast, bucko.
A company called Phoenix Systems is trying to debunk all that and offer that a much better indicator of impending brake system corrosion is dissolved copper, which comes from various parts of brake lines and valves and other plumbing as the corrosion inhibitors in the fluid lose effectiveness. After a bunch of studies, SAE papers, and testing hundreds of real-life on-road vehicles, they've come up with these test strips that turn various shades of purple to indicate parts per million of copper and are supposed to be about the last and best word on the condition of a car's brake fluid. Dip, wait, and compare; it's supposed to be easy as that. |
The NCF does mention that some parts of the brake system are made from
newer low-corrosion materials such as phenol-resin wheel pistons, but most
of the other parts -- valves, pumps, tubing -- are likely the same typical
brake plumbing found on any other car. And most importantly, if the brake
lines are made in the standard manner they've got plenty of copper to deliver
into bad brake fluid that attacks it. While the Phoenix information is
quick to point out many times over how their strips are NOT a moisture test,
one would think that after this amount of time *some* sort of perceptible
change would have happened. On the other hand, the stuff in the reservoir
has been exactly the same golden color the entire time, whereas the brake
fluid visible in many other cars is often a deep brown crud color and still
goin'.
Hmmm. What to do, what to do. This prompted a bit of deeper study on the subject, and eventually a call to Phoenix and a very entertaining and productive discussion with one of their staff. They have some interesting whitepapers on their website about brake-fluid chemistry and the product history, which I list in the reference section. I had read some of these before calling, so as soon as our conversation got going the guy knew I'd at least done a little homework. And he was very intrigued to learn of a car showing virtually *no* dissolved copper at over 100K miles! Perhaps there was something going on here that was about to shoot holes in the theory that PPM of copper in brake fluid advances fairly linearly over time no matter what you do? I floated the idea that since the lines out to the wheels are long dead-ends, perhaps the condition of the fluid at the wheel cylinders might be different and any changed chemistry there might never get the chance to make it back to the rest of the hydraulic system and the reservoir. Clearly, we agreed, the right thing to do was draw a sample at one of the rear brakes, to get as far away from the reservoir as possible, and see what was going on there. Meaning: open up one of the bleeder fittings, which I've never done.
It is possible to become VERY paranoid about screwing around with the brake hydraulics at all in a Prius, as all the forum pundits basically agree that anything involving bleeding the system needs an OEM-level scantool and strict attention to the procedure in the service manual. However, a DIYer's best tool is a solid understanding of any system, and what one can or cannot do with the car in different running states. One of the intangible but huge benefits of having the pressure monitors on my own system is that better understanding, as it allows seeing exactly when and about how much hydraulic pressure is sent to the front or rear wheels. Reading between the lines in the manual section hints strongly that the front brakes are best bled with the brake system depressurized and in its hydraulic-only backup mode, as shown here with most of the solenoid valves in their rest position, but the rears are done with the whole car powered *up* with full boosted brake pressure on tap. And no pedal-pumping, as the brake ECU will promptly send in more fluid to make up for any rear-line pressure drop all by itself. That has the happy consequence that rear bleeding can be a one-person job. |
The bleed fitting has a little rubber cap over it. Well, it should; my car's been missing one of them on a front wheel for years. |
The test is performed ... |
... and if anything, comes up with a *better* result than from the reservoir up front, even after a couple of minutes of letting it soak in. |
Most perplexing.
If Toyota had designed a whole new suite of brake parts that somehow magically prevented its fluid from degrading over time, they would have likely made much more ballyhoo about it in documents like the NCF and even the maintenance schedule. As it is, brake fluid is never actually *mentioned* in the Prius maintenance "passport" as a service item, leaving even the Toyota technicians to guess and/or try to upsell brake-flush services that might be completely unnecessary. However, Toyota may have indirectly provided something which extends brake fluid life longer than expected -- the hybrid system! Again, judicious use of regen lets me complete the majority of my trips with stone-cold brakes at all four corners, and only when playing in the mountains or during the occasional yellow-light hard stop do they ever get any real work to do. Finding this excerpt in one of the papers hosted by Phoenix ... The thermal effects on brake fluid while operating in a system are very important to the longevity of the brake fluid. When there is no thermal activity, i.e. vehicle sitting on a dealer lot for 1 year, there is little to no effect of thermal oxidation on the brake fluid. That is why brake fluid still appears as if new prior to the vehicle being driven. Copper levels have been found to directly represent the thermal effects on brake fluid condition in a vehicular braking system. ... The thermal effects wear the brake fluid. That is one reason why a vehicle may have only 12,000 miles, but due to the thermal effects of the brake fluid, as well as others, it may have a "virtual age" to that of brake fluid with 30,000 or more miles. This condition has been demonstrated on extreme demand vehicles that are repeatedly subjected to high amounts of heat.lets me more readily believe that there's nothing more magic going on here than a really low usage factor, which is also reflected in the amount of pad wear. |
Go to Part 2: Under-hood stuff