TR2/3/3A Pushing down the clutch pedal when starting the car?

[karls59tr]

I've been told that this can be hard on crankshaft thrust bearings? Is this so for a TR3? I hear that Spitfire engines have an issue with thrust bearings so maybe it;s just that model?

 

[NutmegCT]

Karl - in every manual gearbox car I've owned since the 1960s, the operator's manual indicated *not* to use the clutch when starting the engine.

Gearbox in neutral, start the engine. Use the clutch to change gears only.

But many of today's cars (the ones with manual transmissions) require both the clutch and the brake to be pushed down in order to start the car.

Hope this helps.
Tom M.

 

[mctriumph]

The 2 liter cars had very robust thrust washers unlike the later motors. These only fail when you run the motor
out of oil (along with everything else). It is recommended to NEVER run your motor out of oil, unless you like
long walks ....
Mad dog

 

[Sarastro]

I don't see why pushing on the clutch while starting should introduce any more force on the thrust bearings than when the engine is running.

That said, it's not necessary. Just be sure the transmission is in neutral.

 

[bobhustead]

I don't know where people, including those who write the manuals Tom mentions, get these nutty ideas (although it does slow the starter a bit). A starter turns the engine at 300 RPM or so. It turns 10 seconds until it starts. This is 50 crank turns. Don't talk to me about the times it is slow to start. Oil pressure builds from the first turns of the cam (oil pump). This oil leaks down onto the thrust bearings very quickly. Leakage is the same way they get lube while running. What the heck (Basil provided the "heck") is the problem. Might we hypothesize that the crank mounted fan puts forward pressure on the crank and thrust bearings every second the engine is running, so we should throw the factory fan away and use only supplemental electric fans? These cars are machines that are designed for an extreme amount of abuse. Imagine the flattening force applied to a rod bearing (same material as thrust washers) when, at 175 psi of ambient pressure, there is a sudden explosion that ups pressure to 1000 psi. Those are the numbers. That's what the rod hits the crank at. The wear of turning the engine with the clutch in is of absolutely no fargin consequence.
Bob

 

[CJD]

The water gets muddier when modern cars will NOT start unless you have the clutch pushed in!?!

Personally, I have never thought about it. Sometimes I use the clutch, and other times I don't.

 

[charlie74]

Might we hypothesize that the crank mounted fan puts forward pressure on the crank and thrust bearings every second the engine is running, so we should throw the factory fan away and use only supplemental electric fans?

When the engine is running then perhaps yes but at idle it’s probably negligible. Certainly there wont be any when only at “300 rpm” or zero…

Over the years everything I have read about excessive wear on the crank thrust washers is due to starting the car with the clutch pedal depressed or sitting at a light and doing the same thing. I have the upgraded TW’s in my car and intend to change nothing about my clutch use or startup.

Modern cars have a clutch interlock as a safety precaution because there was probably one too many idiots who tried to start their car in gear and it ran over their kids/kids bikes or it wound up in their living rooms or on the street with a garage door draped over the hood…

 

[karls59tr]

When the engine is running then perhaps yes but at idle it’s probably negligible. Certainly there wont be any when only at “300 rpm” or zero…

Over the years everything I have read about excessive wear on the crank thrust washers is due to starting the car with the clutch pedal depressed or sitting at a light and doing the same thing. I have the upgraded TW’s in my car and intend to change nothing about my clutch use or startup.

Modern cars have a clutch interlock as a safety precaution because there was probably one too many idiots who tried to start their car in gear and it ran over their kids/kids bikes or it wound up in their living rooms or on the street with a garage door draped over the hood…

If you push in the clutch pedal at every stop light dosn't that shorten the clutch life?

 

[charlie74]

That too…

 

[NutmegCT]

I'm thinking that the issue isn't just "pushing in the clutch pedal" - it's pushing it in and *holding* it in, like at a stop light, or in a traffic jam.

 

[CJD]

As long as the engine is running, the crankshaft thrust bearing is pressure lubricated...so that is not a problem. During starting, there is no oil pressure to the thrust bearing...so I see where it could be an issue. Sitting at a stop light, then, would not be a problem. The clutch fork throw-out bearing would be the worry there.

 

[mgedit]

In nearly 60 years of driving, it’s what I’ve always done. That was how I was told to start ‘er up when I first learned. No mechanical issues, and never had a car jump forward when started in gear by mistake. Maybe not “correct”, just my experience. Cheers, Mike

 

[JHaydon]

Properly-designed thrust washers, with the correct clutch and properly-adjusted clutch mechanism, will not have a problem. As others have said, the engineers anticipated the force of disengaging the clutch; also, the thrust washers get oil within moments of the starter cranking.

If the clutch takes significantly more force to release than stock (e.g., racing clutch) or if the clutch release over-strokes (a HUGE problem with hydraulic release bearings), the crank can be pushed forward with more force than what the engineers anticipated. We saw that several years ago when a bunch of FF1600s blew their engines at the Runoffs -- in (almost) every case, the HRB was over-stroked, which causes a massive pressure spike in the system.

Idling for extended periods with the clutch disengaged spins the clutch release bearing, which is (generally) not designed for extended periods of spinning with pressure applied. It's happy to spin freely or to spin under pressure for several seconds, but the full duration of a red light is pushing it.

Again, echoing others -- I have other owners' manuals from equally old cars (or older) instructing you to disengage the clutch before touching the starter. I have done it both ways -- disengaging purely out of paranoia -- and always sweat just a little when I crank without disengaging.

 

[mezy]

When i left school and started working on agricultural machinery, including tractors, some had to have the clutch depressed
at least to the first stage in order to start it, so for me it became a habit,
I had friends in those days driving cars which had gear sticks like pudding stirers and was a bit of a lotery finding the right gear,
on more than one ocation they had lurched forward thinking they were in neutral when they were not.