Terrible mechanical design decisions

[Alexander B]

In this topic, discus things you think are terribly designed by car manufacturers.
Perhaps something got ruined by the pencil pushers after a cost saving attempt.
Perhaps it just evolved that way from re-using existing parts.
Perhaps they just let the unpaid intern design it.
Perhaps it was designed on Friday afternoon when they just wanted to go home and didn’t care.
Who knows what happened, but its terrible if you have to work on it.

Some examples that come to mind from my Renault Mégane, after owning it 2 weeks:
Timing belt gears not keyed to the camshafts or crankshaft, flywheel (with crank position teeth) also not keyed to the crankshaft (1/7 chance of getting it back on correctly if you removed it without marking.)
Gearbox shift linkage connects on the underside, its leaky and damage-prone.
Unbolting the lower ball joint requires removal of the brake caliper to be able to get the bolt out.
The CV boot bolts to the gearbox and is also the shaft seal, the inner CV is filled with transmission oil, and a failed boot also kills the gearbox.
Subframe in the way of everything, I guess its normal on a lot of cars, but I’m used to cars where the gearbox just unbolts and drops out the bottom.
Things like engine mounts and bell housing using 3 different bolts to be bolted on, why not 3 of the same bolt, geez.

Some from Citroën:
TU5J4 engine, the intake manifold is difficult to unbolt, I had to cut up a 10mm wrench to have enough room to unbolt the nut closes to the engine mount, and the 2 nuts on the end only fit with an open-end wrench. Allen heads would fit so much better, but then there would be no studs.
TUD5 engine: have to unbolt the engine mount to get the exhaust manifold off, the manifold unbolts, but impacts the mount before it clears the studs.
TUD5 engine: the timing belt idler moved a bit compared to the gasoline version, and is no longer accessible from the little access window.
AX heater matrix, AX type 1 matrix had removable pipes, AX type 2 matrix has molded on solid pipes that require the entire dash to come out for replacement. type 1 still fits just the same though, and can be installed in a type 2 by just removing the glove box (7 screws), but the dealer doesn’t (officially) know that, charging a ton of extra labor to save pennies on a cheaper to produce part.
Rear suspension torsion bar spring held in place with an M8 bolt with a shallow T40 torx head, if you’re not super careful and/or they rust out, they strip and become impossible to remove. a regular hex bolt (or something with a deeper head) would’ve fit just fine too.
Having to remove the floor mat to access the rear nuts of the suspension control arm instead of being bolted from the underside like most other cars, including other Citroën cars.

There is probably more, but most of these caused me frustration or anger at one point or another. So lets see, what weird design choices or unreachable bolts have caused you to have a bad time?

Topic

[James P Grosso]

Plastic heater cores and intercoolers.

Although not a bad design, but a pain to replace would be the chain driven waterpump on a Pontiac Grand Am quad4 engine. It’s between the back of the block and firewall, and besides the fact it is chain driven, it also bolts to the block, front cover and thermost housing.

[Greg]

Chrysler 2.7 engine.

[Mike]

Remember the Chrysler Concorde, and its Dodge and Eagle “cab forward” siblings? (These cars weren’t really cab forward vehicles in the true sense of the term; it was just a marketing gimmick. But that’s a topic for another discussion.)

I hated those shrink-wrapped abominations. You actually had to remove a wheel to access the battery. Terrible.

[Noah]

Coil packs on the gen 4 Ford Taurus. Mounted to the valve cover with no real heat protection, not to mention the poor quality part to begin with.

Any engines where the alternator is also the belt tensioner (much easier to have a separate tensioner)

[Alexander B]

I’m kind of on the fence on that last one, if the alternator is also the only thing being driven, why does it need a tensioner pulley (that can wear out and costs money to replace) if it could just as well just had a slotted mount.

May be specific to my car though. 🙂

[Sam Roodman]

Any chrysler product where the cps is pinned by the firewall. Especially the trucks.

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[Noah]

It makes sense if the alternator is the only thing belt driven. Last alternator I changed was on a Toyota paseo where the alternator, AC compressor, PS pump and water pump were all driven off the serpentine belt. Would have been a lot easier if it had a separate tensioner. Another reason to advocate for a tensioner: They CAN be placed in a more convenient location when the mfg chooses to. Makes belt changes much easier than having to loosen the bolt on an alternator.

[Rick Cropper]

Pretty much all of the European trash build in the last 30 years.

Audi timing chains – the ones on the back of the engine under the bell housing. Have to remove engine or transmission (or both) to service. Some years like to let go before 100k and bend up valves. Nice.

Ford modular engines. Timing chains guides made from the tears of foreign child labor. Also very difficult to work on even in a truck body. That pretty much goes for all Fords though. I haven’t met one yet that I liked. :angry:

What really illustrates how bad the designs are is when you have spent many years working on a brand like Subaru or Honda where, for the most part, things are relatively easy to work on and reliable. Then someone hands you an Audi, or a BMW and the lack of design forethought just smacks you in the face and saps your will to live. If you haven’t known any better then you will probably be more willing to accept it. But when you do you just want to tell the customer to sell it and buy something that doesn’t complicate your life or theirs.

Rick

[Wyr Twister]

[quote=”Evil-i” post=178192]Remember the Chrysler Concorde, and its Dodge and Eagle “cab forward” siblings? (These cars weren’t really cab forward vehicles in the true sense of the term; it was just a marketing gimmick. But that’s a topic for another discussion.)

I hated those shrink-wrapped abominations. You actually had to remove a wheel to access the battery. Terrible.[/quote]

I helped a cousin replace a battery in a Chrysler that was like that . What were those idiots thinking ? !

It appears that cars , for the most part , are designed to go together quickly and cheaply as they go down the assembly line . No thought to repairs latter down the road .

God bless
Wyr

[Greg]

Any vehicle that puts the engine ecm next to the battery.

[Bluesnut]

The early Subaru automatic transmissions used a nylon govenor drive gear to drive a steel driven gear. So over time the nylon gear gives up and the entire transmission has to be diassembled to replace on expensive nylon gear with another.

Four years or so it took for them to realize the govenor drive gear should be steel; not nylon. So the change was made. Then what happened was the nylon driven gear (which was now nylon) was stripping out. At least in this case the repair could be done without too much trouble.

Finally it soaked in that steel on steel is the answer.

As for Subaru head gaskets; they’ve had that issue since the early 70s.

[Author]

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