Archive for the ‘Geared Encounters’ Category

We have seen a large number of Toyotas with this slow forming cancer with potentially catastrophic results. Take a look at the pic below… Where’s Waldo


There he is!
This 2002 Tacoma was the most recent case of this phenomena.
The vehicle came in with the performance complaint of no power and heavy exhaust smell. A quick scan brought up trouble codes for oxygen sensors and fuel control near limits. Idle was slightly rough but acceptable.  The exhaust smelled rich which could be expected. Scan data ruled out plugged exhaust but showed that the computer was loosing a battle constantly trying to lean out a runaway mixture.

Having seen this many times before I decided to inspect the lower timing cover for signs od coolant leakage or residue near the lower timing cover while pressurizing the radiator. This is the area where coolant makes its way out of the timing cover when the water pump leaks. This one looked clean. We detached the upper timing cover to examine the synchronization of the camshafts and crankshaft and what we saw confirmed our suspicion that the timing belt had skipped four teeth on one cam ans two on the other. Now, I should say that we see what we call “jumped time” often and that by itself does not a phenomenon make. However deeper behind the mid and lower covers lied the automotive equivalent of kidney stones or perhaps an artery jamming clot of cholesterol. The infamous Waldo in this case was an ever so slow coolant leak. Too slow to leave a mark on the garage floor, too slow to show up as anything more alarming than a quart top off at each oil change, and too slow to cause an overheat. These water pumps can leak so slow that the hot coolant that leaks out instantly evaporates on the hot engine surface insulated by the timing cover. When the moisture evaporates the residue left behind accumulates and forms shale like stones that eventually beak off of the surface and fall into the cogs and sprockets below forcing enough stretch in the timing belt to disengage the teeth and skip enough teeth to cause the whole problem. If the timing belt breaks or enough teeth are jumped at a high enough engine speed the motor will be destroyed.

We can check this with a special snake spy camera that can view this area without having to disassemble the entire timing cover.


This car is a good illustration of one of the many ways that timing belts fail.


As you can see, visual inspection wouldn’t have tipped anyone off that failure was coming!

Hello boys and girls, welcome to pattern-failure corner. This round it’s time to cover one of the most popular roof-racked, top-heavy rolling toasters prevalent in the used car market. You guessed it, I’m talking about the Nissan Xterra of vintage 2001-2004. These babies exploded onto the market back in their day most commonly equipped with a 3.3L V6 engine. Their collective gear ratios provided a vehicle ideal for grocery fetching house-spouses and teenagers alike in that they both are well served with an underpowered, oversized rig with plenty of crumple room to protect the occupants. Don’t get me wrong, overall I like these vehicles for my customers. They have fewer common failures, are reasonable on maintenance and seem to be a pretty good buy from the standpoint of total ownership cost over the life of the vehicle and likewise a safe 100,000 mile used buy for the kiddo.
For my taste, however, this rig falls short. It still escapes me that the designers of these rigs chose the geared ratios that barely moved these rigs up any hill without downshifting into a near-redline vibrating engine roar that is loud enough to just make me uneasy. Like a nervous astronaut riding the rocket as it tries to escape earth’s atmosphere. But wait… it’s not the Challenger, Columbia, or Enterprise and we’re not headed for the moon… Its just an Xterra fighting with every ounce of guts to ascend the I-70 corridor. Personally, I just don’t want to feel like I’m taxing my rig out at 98% capacity when climbing the last mile up to Eisenhower tunnel.
Not so fast though… It’s not fair to single out this specific make and model as a slug. Equally power-band challenged are Toyota’s 3.0L, and 3.4L equipped Tacomas and 4Runners made over the span of nearly a decade and a half. What makes the Xterra stand out from my perspective is its physique, reminiscent of the late-eighties, early nineties Isuzu troopers. Tall, narrow, and toaster like yet ever popular as a top seller in its time. Additionally etched into my perspective are the pattern failures that we have been seeing on these ever-popular vehicles. Namely burnt electrical component at the fuel tank and paper thin aluminum walls bursting and purging antifreeze from the engine.
Rest on your rump, your ride is as dead as a stump, and its all because of your hot-headed pump.

If you own a Chrysler, Chevy, or Ford, you may have already become intimately familiar with the perils of a dying fuel pump. Nissan in general however is not as common to see pump failures. As many motor driven pumps do in their death spiral excessive current draw taxes circuits and expedites deteriorating connections to the point of metal turned to ash and a tow bill for the record pouch. Check out this particular pattern failure. You can see in the picture this common path of greatest weakness where the fuel pump circuit seems to burn through the metal and plastic in this top-cap that seals the gas tank. Don’t fret, the circuit is still safe as the fuse protects from developing enough heat to create an ignition. However, over time this seems to happen to nearly all Xterras right around 110,000 miles.

Remember what happened to the wicked witch of the west when she was splashed with water? Well recently I have begun wondering if it was 80,000 mile old engine water that they used, and please don’t get any on me! As acids are known to attack metals such as aluminum, acidic coolant degraded over time in the Xterra engine erode the walls of cast aluminum water jackets on their engines until their paper thin walls burst into leaks and overheats. Because of this prevalence, and the coincidence of their mileage-timing, we have been recommending replacement of these bolt-on aluminum parts with timing belt jobs so that the timing belt doesn’t have to be disassembled shortly after to replace these repeated offenders. It’s a differentiator that only experience provides. Just like an oil pump seal on a 2.5L Subaru, if these aren’t recommended with a timing belt job then your guy doesn’t have the experience to warrant you trust. Most of these failures have very subtle signs that are difficult to see when assembled yet become obvious once torn apart. Rather than getting a call once your rig is torn apart, you should be prepped in advance.

By far one of the most common transmissions in domestic GM trucks and SUVs the 4L60e is not without its own select set of common failures, design weaknesses, and aftermarket solutions.

On this 2001 1500 Silverado, one of the planetary assemblies decided to come apart at the center splined hub. Also, we often see reaction sun shells that crack and shear at the hub. Thats why we install “The Beast”, an aftermarket solution to this original design weakness. The Beast, is substantially thicker in the hub area and is pre-tempered for additional strength. I have yet to see or hear of one of these upgraded sun shells failing.

Another trouble code fix for these transmissions is the Trans-Go valve body spacer plate upgrade. Not only do we incorporate one of these into every 4L60e build that we do, but we are always impressed at the improved shift quality, and performance brought from the engineered improvements into the various flow passages in this plate. Just about every 4L60e we see has a valve body spacer plate with check ball ports mannered, dished and sometimes blown through. About one third have broken accumulator springs.