Tell me I'm correct (or wrong if I am!)

[Fastpedeller]

Unsure whether to put this in braking or engines/drivetrain. Consider the latter to be correct but mods please move if you wish.
Anyway, to subject. Bought new car, in handbook it says:-

Parking Brake:- If you park your vehicle on a hill and facing downhill select reverse gear and turn the steering wheel towards the kerb.

I have always understood if a vehicle was to roll away in gear the engine compression will stop it, also the engine should NEVER be turned backwards, as it's not designed to do that. Therefore if facing downhill the car should be in a FORWARD gear, and if it rolls it will be prevented by the engine compression.

Am I correct? or is the vehicle manufacturer correct?

[Happy Jim]

You are wrong :-)

The engine only turns in one direction....that's why you have a reverse gear ;-)

[PoleDriver]

Happy Jim said:

You are wrong :-)

The engine only turns in one direction....that's why you have a reverse gear ;-)

Really? So what stops it from turning backwards?

[Hugo a Gogo]

it might well be forced to turn backwards if the brake failed, and it's possible that could cause damage, skipping a timing chain or slipping some tensioner or something

not likely if it only rolls a few inches though

[stevieturbo]

Fastpedeller said:

Unsure whether to put this in braking or engines/drivetrain. Consider the latter to be correct but mods please move if you wish.
Anyway, to subject. Bought new car, in handbook it says:-

Parking Brake:- If you park your vehicle on a hill and facing downhill select reverse gear and turn the steering wheel towards the kerb.

I have always understood if a vehicle was to roll away in gear the engine compression will stop it, also the engine should NEVER be turned backwards, as it's not designed to do that. Therefore if facing downhill the car should be in a FORWARD gear, and if it rolls it will be prevented by the engine compression.

Am I correct? or is the vehicle manufacturer correct?

Some engines wont be particularly bothered about turning backwards.

Many modern ste engines with stupid hydraulic tensioners on chains etc....turning them backwards could spell death.

So yes it really does sound like bad advice to do anything that would encourage an engine to rotate in the wrong direction.

[sunbeam alpine]

Happy Jim said:

You are wrong :-)

The engine only turns in one direction....that's why you have a reverse gear ;-)

Surely this has to be the correct answer?

[Fastpedeller]

sunbeam alpine said:

Happy Jim said:

You are wrong :-)

The engine only turns in one direction....that's why you have a reverse gear ;-)

Surely this has to be the correct answer?

It only turns in one direction WHEN IT IS RUNNING.... but if it's forced (by gravity pulling the car downhill) to turn in the opposite direction because the car is in reverse gear what then happens?

[PoleDriver]

Fastpedeller said:

It only turns in one direction WHEN IT IS RUNNING.... but if it's forced (by gravity pulling the car downhill) to turn in the opposite direction because the car is in reverse gear what then happens?

We're getting warmer!

[Stan Weiss]

I guess I must be the only one here that has ever used a positive piston stop to find / verify TDC with pointer and degree wheel on an assembled engine.

Stan

[Steve_D]

Stan Weiss said:

I guess I must be the only one here that has ever used a positive piston stop to find / verify TDC with pointer and degree wheel on an assembled engine.

Stan

No, you are not alone.
There would have to be something wrong if an engine cannot be turned backwards.

Steve

[stevieturbo]

Stan Weiss said:

I guess I must be the only one here that has ever used a positive piston stop to find / verify TDC with pointer and degree wheel on an assembled engine.

Stan

And you are turning the engine over in a more controlled manner....and probably an engine that doesnt have silly hydraulic tensioners etc

It isnt the same thing.

Obviously the handbrake should always work, and the car should never be placed in a scenario where the vehicle moving unattended can turn the engine over in either direction, but there is a risk of engine damage if the engine was to get rotated the wrong way under such circumstances on some engines.

[Little Pete]

It really depends on the engine type. Most OHC that are belt driven would be ok but chain driven/hydraulic tensioner types wouldn't.
A Transit 2.4 for example would be trashed if it turned anti clockwise.

[GreenV8S]

Little Pete said:

A Transit 2.4 for example would be trashed if it turned anti clockwise.

What's the failure mechanism?

[Mr E]

Saabs mandated reverse gear when parked (you can't remove the key unless it's in reverse).

[stevieturbo]

GreenV8S said:

What's the failure mechanism?

Simple.

No tension applied, jumps chain teeth because it's turning into the slack side or worse dislodges chain.

Try to start engine and it destroys itself.

[KiaDiseasel]

What a silly thread. The handbook says X. Do X. End of story. What other engines do when they're turned backwards is neither here nor there.

[Little Pete]

stevieturbo said:

Simple.

No tension applied, jumps chain teeth because it's turning into the slack side or worse dislodges chain.

Try to start engine and it destroys itself.

This in a nutshell. There's not enough strength in the internal spring in the tensioner to keep the chain tight.
I wouldn't bump start one either!

Edited by Little Pete on Sunday 30th October 12:29

[anonymous-user]

It's got nothing to do with the engine being turned "backwards" and everything to do with what happens when you jump back into thr car, and go to start it, forgetting it's in gear, back when cars let you do that sort of thing!

(if you'd put it in first, start in gear would, fire up, and zoom off down the hill. but in reverse, either the starter wouldn't be man enough to fire it up, or having to lift the car up the hill would just stall it out straight away)

[PoleDriver]

We have a winner!

[stevieturbo]

Max_Torque said:

It's got nothing to do with the engine being turned "backwards" and everything to do with what happens when you jump back into thr car, and go to start it, forgetting it's in gear, back when cars let you do that sort of thing!

(if you'd put it in first, start in gear would, fire up, and zoom off down the hill. but in reverse, either the starter wouldn't be man enough to fire it up, or having to lift the car up the hill would just stall it out straight away)

In many ways this stuff annoys me.

Automated lights, wipers, DRL's ( although full F/R DRL's should be compulsory...front only is just bloody stupid ) etc etc and including features that might prevent some retard crashing as they start a parked car

If aholes are so fking incompetent this sort of stuff is becoming standard...almost being necessary, it just highlights how many people should never be allowed behind the wheel of a car.