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jamesmckenzie

Engine loaded fresh after rebuild - possible complaints

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Hello all,

 

I had the top end (3.2) rebuilt at a cost of £10k last year (replating barrels, snapped head studs, valves, chains, cams, clutch, exhaust etc). The engine was filled with mineral oil and I was instructed to drive regular duty cycles (not labour the engine) for 1500 miles until the engine bed-in, the oil could be changed and the heads re-tensioned. 

Long story short. The car has not been driven for 18 months and has now undergone light commissioning (brakes). The garage (not the same one who did  the rebuild) has driven the car and reports that there is a transmission noise 'under load.' (There was no transmission noise noted from the engine builder when they ran the car after build was completed).

I explicitly told the mechanic not to load the engine (as was told me). 

I would like to know what possible concerns could eventuate from an engine that has been loaded in its bedding in stage before I go and pay any money (and take back the keys).

I don't yet know what the garage meant by 'under load' just yet - I'd just like to have some ammunition when i go in later today.

This whole thing has left me rattled.

Thanks very much.

James

 

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Think I’d be inclined to ask them what they mean by under load. It might just mean being driven rather than taken high up in the rev range.

Also, ask them to get in with you and show you the transmission noise on the road. You can the hear it yourself and make a judgement call maybe.

I'm sure an engine expert will be along shortly to tell you what potentially can be harmed by high revs on a fresh build. I don’t think it will hurt if not sustained as running in is really about changing the revs and load as much as possible rather than sitting at a certain rev range and gear as on a motorway. 

Hope they haven’t damaged it for you 🤞

Edited by Busybee
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These engines are pretty strong, bedding in means not redlining it for the first 1000 miles or so. The engine will be under load at 4 or 5K, shouldnt be a problem

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Have you done the 1500 miles or not?

I bet the noise is the G50 rattle. :twocents:

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30 minutes ago, Dr Rock said:

I bet the noise is the G50 rattle. :twocents:

+1 

to the uninitiated that rattle wouldn’t sound right. What gearbox mounts do you have in the bar? It can be quite loud with superpros I have found. 

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It reads like two separate issues: transmission noise - if genuinely from the transmission - cannot be related to an engine rebuild.

 

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2 hours ago, Busybee said:

Think I’d be inclined to ask them what they mean by under load.  

Im no expert, but from my experience, loading is running in too high a gear for the engine speed (solved by a downshift to prevent the engine bogging down)

Im unclear what issues loading causes, however.

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I would have interpreted 'under load' as not on a trailing throttle and would view it quite differently from 'labouring' which would be running in an inappropriately high gear?

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6 minutes ago, Roy M said:

I would have interpreted 'under load' as not on a trailing throttle and would view it quite differently from 'labouring' which would be running in an inappropriately high gear?

+1 What Roy said

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19 minutes ago, Roy M said:

I would have interpreted 'under load' as not on a trailing throttle and would view it quite differently from 'labouring' which would be running in an inappropriately high gear?

I did say I wasn’t an expert :)

Whats a trailing throttle?

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Thanks all. Here's the analysis... And I quote.

'We are fully aware that the engine has not been run in and it has not been rotated over 4000 rpm nor has it been overloaded. The gearbox makes the noise when driving at around 40 mph in the upper gears. It’s just a drivers comment, we haven’t been testing the engine or the gearbox. If you get here in time this morning I’ll go out for a drive with you.

This (and your comments) puts my heart at rest.

Dr. Rock/Wingnonut what is the G50 rattle and does this analysis describe it?

Champions,

James

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35 minutes ago, jamesmckenzie said:

Thanks all. Here's the analysis... And I quote.

'We are fully aware that the engine has not been run in and it has not been rotated over 4000 rpm nor has it been overloaded. The gearbox makes the noise when driving at around 40 mph in the upper gears. It’s just a drivers comment, we haven’t been testing the engine or the gearbox. If you get here in time this morning I’ll go out for a drive with you.

This (and your comments) puts my heart at rest.

Dr. Rock/Wingnonut what is the G50 rattle and does this analysis describe it?

Sounds like it to me. 

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1 hour ago, SP72 said:

I did say I wasn’t an expert :)

Whats a trailing throttle?

Trailing throttle us basically when you're not accelerating - when you back off the accelerator then you're on a trailing throttle 

Except for the lucky few none of us are experts which is why the help on this forum is so useful. I've always found the help given very supportive and long may it continue!

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The infamous G50 rattle as I understand it. 40mph in 5th, than slowed to under 40 in fifth:

 

Edited by Dr Rock

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4 hours ago, SP72 said:

I did say I wasn’t an expert :)

Whats a trailing throttle?

You just keep that loverly new engine of yours under moderate load till it’s fully run in and you’ll hopefully not have to worry about labouring 👍. Is it a G50 box in yours? 

1 hour ago, Dr Rock said:

The infamous G50 rattle as I understand it. 40mph in 5th, than slowed to under 40 in fifth:

 

Not having a g50, that does sound like a flipping coffee grinder. Would scare the **** out of me. What causes it? 

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Gents,

 

I cant hear any sound from that video - yet I can from other youtube clips. What can i do?

Also, what is the root cause of the so called 'G50 rattle'?

 

James

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1 hour ago, Busybee said:

You just keep that loverly new engine of yours under moderate load till it’s fully run in and you’ll hopefully not have to worry about labouring 👍. Is it a G50 box in yours? 

Not having a g50, that does sound like a flipping coffee grinder. Would scare the **** out of me. What causes it? 

Do you not have the 915 rattle on your SC when the engine is idling in neutral?

 

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Just now, Leicestershire said:

Do you not have the 915 rattle on your SC when the engine is idling in neutral?

Don’t think so. Is that another “thing”? 

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29 minutes ago, Busybee said:

Don’t think so. Is that another “thing”? 

It’s just the shifter mechanism in the bottom of the gearbox rattling.

Common feature on 915 transmissions and often identified as a fault.

Have a listen next time you are at the rear of the car with the engine running. It usually gets louder when the gear oil is hot.

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On 5/26/2018 at 7:13 PM, jamesmckenzie said:

Also, what is the root cause of the so called 'G50 rattle'?

 

Have a search on here. Its one of those they all do that things. Porsche released a technical bulletin for the fix, which actual involves a rubber band (with its own part number lol) being fitted to the shifter mechanism. It takes up some tension removing the rattle.

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In regards to running in rebuild engines, I have heard mileage ranges from 500 to 1500, most saying slowly build up the Rev ranges as mileage increases but never red line it.

What are people’s experiences and/or what their engine builders have recommended?

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Hi all,

So got the car back today and it's horrendous! I don't remember this noise as bad as this before I have it to them. Sounds like someones pulling a train of large ball bearings over the top of the engine, kind of what I'd imagine chain backlash would sound like.

And the sound is large (not just in 4th and 5th but) in 3rd gear under anything but light acceleration.

Wingnonut, you mentioned particular gearbox mounts in the bar. What does this mean? Could these have perished amplifying a noise?

Car has done 70k miles.

Warmest,

James.

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James, maybe you are worrying too much?....these engines are not quiet! Would it be possible to post a video of the engine running, and that way would enable a lot of very learned gentlemen to voice an informed opinion on it?

David

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