Jump to content
  • Welcome to AutoLanka

    :action-smiley-028: We found you speeding on AutoLanka Forums without any registration! If you want the best experience, please sign in. Safe driving! 

  • 0
jake_harper

After An Engine Overhaul

Question

Does an engine actually need special attention after an overhaul? (assuming the mechanic has done a perfect job)

What is the reason behind driving at a moderate speed (40) for a while? Or is it a baseless precaution?

Share this post


Link to post
Share on other sites

19 answers to this question

Recommended Posts

  • 0

the idea is to drive at moderate engine speeds and not over rev the engine. same goes for brand new vehicles. the reason for this is the pistons and cylinder linings are new and there are slight imperfections on them so they need to form grooves on them to slide against each other smoothly. after 10000 kms your engine will be nicely run in.

So don't wast time driving at 40 all the time or give the engine a hard time accelerating hard to 40. just keep the revs below 2000 rpm and you should be ok.

Share this post


Link to post
Share on other sites
  • 0

I don't know what the serious damage is but i'm guessing its along the lines of overheating.

I once pushed an overhauled engine a little hard and pierced a hole in the oil cooler. because everything is working at factory tolerances and optimal pressure the weaker parts could give in. anyway in a real rebuild all worn parts must be replaced so I guess it was worth it.

Share this post


Link to post
Share on other sites
  • 0

Does an engine actually need special attention after an overhaul? (assuming the mechanic has done a perfect job)

What is the reason behind driving at a moderate speed (40) for a while? Or is it a baseless precaution?

'jake_harper',

During good old days when we do a full engine overhaul, we used to do a bench test run continuously for 24 hours, with a mechanic near the engine monitoring the temperature, oil pressure and RPM, all said meters was fitted externally on front of the mechanic so that he can monitor. RPM we set to 1000. Thereafter only we fix the engine to motor vehicle and stat a road test. I used to go on to my land 75 miles away from Colombo, at about 35 miles maximum speed, with the owner and give the vehicle to the owner after that. At 500 miles after the engine overhaul I get the owner to change oil.

Periodically I used to check the engine after overhaul till the owner does about 2500 miles, finally adjust the tappets and forget about same.

Above is my experience in carburetor engines. Since I gave up my electrical and engine repairs carrier, I have not done any heavy repairs for motor vehicles engines, only one and half years back last Chinese vehicle. I had few problems, I did the repairs my self with my staff, engine and brakes.

Sylvi Wijesinghe.

  • Like 3

Share this post


Link to post
Share on other sites
  • 0

Sylvi thanks for replying. In my case it is a diesel engine. And it is the previous owner who has done the repair. After a rough calculation I doubt the after repair mileage might be less than 10k.

Share this post


Link to post
Share on other sites
  • 0

'jake_harper',

Do you have any problem with the engine any bearing knock or engine is noisy, get a good diesel engine mechanic to test your engine. Do a compression test it will cost you about 1500.00 Rupees.

Then you will come to know about the engine condition.

Sylvi Wijesinghe.

Share this post


Link to post
Share on other sites
  • 0

Its working alright. But by the time I found the engine might be still in the risky zone I drove it the normal way for like 500km. I was worried I might have damaged it.Thanks for the advice.

Share this post


Link to post
Share on other sites
  • 0

I am not quote sure about this running in periods for new engines nowadays. I remember watching this program on discovery where they showed a sports car being assembled, I cant remember the make but after the car was out of the production line it was test driven at very high speeds, and every single car was individually tested.

I think since technology has improved so much they maybe able to make the engine blocks and pistons without any imperfections and so could drive it the way it was built to be driven from the day you purchased it. If you say 10,000k that's a long time for running in a vehicle and that's a long wait . Most cars brought down to SL is less than this ( assuming the millage has not been tampered with ).

Share this post


Link to post
Share on other sites
  • 0

CARBON B4,

All new engines do not need running in period, because technology has advanced with lubricants, so it is not necessary for running in period. All tolerances on bearings are there for thin film of oil to go through.

Sylvi Wijesinghe.

Share this post


Link to post
Share on other sites
  • 0

So then why do people who buy new cars run in the vehicles ? This guy I know bought the new 508 and the agents have said to run it in, so he is driving it very slow below 2k RPM.

Share this post


Link to post
Share on other sites
  • 0

CARBON B4,

Can you climb from Gampola to Nuwareliya on top gear, you have to change gears according to the road conditions. then definitely engine revolution go more than 2000 Rpm.

Sylvi Wijesinghe.

Share this post


Link to post
Share on other sites
  • 0

I just want to clear this up:

Yes machining tolerances have improved a great deal over the past 20 years as far as bearing manufacturing etc is concerned.

Brand new vehicles do NOT need to be kept below 2000rpm for a period of time.

it is impossible to recommend a rev range without knowing the vehicle in question as some engines rev to 5k max some to 7,8,9....it’s all in the engine design of how its intended to make power.

It is RECCOMENDED that a brand new vehicle is not thrashed (revved up to the red line, driven hard, raced, abused etc) until a period of 500 miles (800km) “running in" has been done AND the oil & filter changed.

this is because for those first few hundred miles any "high" spots left in manufacturing will be removed by the normal frictional wear from piston rings, bores etc.

If you abuse an engine too early, the high spots get worn off and the wear continues.

The oil and filter change is required as anything that’s worn off is being carried round the engine in the oil system.

Engines that have been rebuilt should ALWAYS have a running in period. I would always recommend this in any country but (no offence to anyone intended) especially in countries like Sri Lanka.

From what I have seen in the time I’ve spent here, due to lack of spare part availability, and in-formal training corners are cut with most of repair work carried out over here so I wouldn’t expect tolerances to be great.

But regardless of who or where an engine is built a running in period of a rebuilt engine should always be done.

a mate of mine holds the top speed record for road going Cosworths 323KPH.......the guys work is top notch, cost you over double to have an engine built by him compared to his competitors so naturally everything is done precisely with only the best parts used and he still runs engines in under low load only running a few PSI of boost before they are mapped correctly and higher boost run.

If in doubt of how long ago the engine was rebuilt, change the oil and filter now. Be gentle with it for the next 800-1000km then change the oil and filter again.

It may be in your interests to have a compression check done but this will only tell you if the head gasket and piston rings are holding pressure as they should . It will give no indication of bearing wear or small piston slap. So only do this if you are losing power, losing coolant, misfiring or the engine is pinking.

The only way to measure bearing wear is with a micrometer or with a substance such as plastigauge, which requires removal of the sump then big end & main bearing caps one by one as each spot is measured. It’s a time consuming procedure and one I would not carry out unless bearing "knock" is being heard from the engine.

  • Like 1

Share this post


Link to post
Share on other sites
  • 0

sorry about that all being in bold type, i did not realise untill i had posted that it was all in bold!

Share this post


Link to post
Share on other sites
  • 0

Thanks for the comprehensive info, also heard you need to use mineral oil after a overhaul and not synthetic.

Share this post


Link to post
Share on other sites
  • 0

I think somebody already mentioned this but the engine oil and filters would probably need to be changed at more regular intervals than normal. I'll probably do the first change at about 500/1000km and then slowly increase the interval up to 150000km and then go back to the standard routine. This is because the oil will get saturated with metal particles from the newly rebuild engine being run in and this may cause some excessive wear if not removed from the lubrication system.

Share this post


Link to post
Share on other sites
  • 0

can someone please explain to me what is this " muppet or muffett" or whatever shaft adjustment after an engine overhaul ?? thanks in advance

Share this post


Link to post
Share on other sites
  • 0

can someone please explain to me what is this " muppet or muffett" or whatever shaft adjustment after an engine overhaul ?? thanks in advance

'hasmax',

Are you mentioning about tappet adjustment of valves. normaly after about 500 to 1500 killometers mechanics do the final tappet adjustment.

Sylvi Wijesinghe.

  • Like 2

Share this post


Link to post
Share on other sites
  • 0

Ok this is like yonks after the last post. But figured i'd bump this up. Got a 1988 Mazda and did a rebuild on the engine. My right leg is itching to floor it, but I'm grinding my teeth and trying to behave for the first 1000km. Did find this contradictory article though:

http://www.mototuneusa.com/break_in_secrets.htm

How much of it is real though I wonder. Had actually planned to swap out the engine but couldn't find a suitable one so went ahead with the overhaul.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Register for a new account in our community. It's easy and FREE!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now




×