12HT Engine noise after overhauling and its checklist

Submitted: Thursday, Sep 05, 2013 at 23:07
ThreadID: 104196 Views:4453 Replies:15 FollowUps:11
This Thread has been Archived
I recently overhauled my 12HT engine and I think there is excessive noise. Whenever I am on high RPM on low gear I felt something is hitting inside the engine somewhat fast like ‘tak-tak-tak’ and then at the same time there is the normal sound of the diesel engine humming . My mechanic is a petrol engine expert and he and is pretty sure he has overhauled it correctly.

I wanted to know is there any way to determine through engine sound on the engine condition? Or is there any testing checklist to make sure on engine condition.

I recently went on long trip but had to return back as I noticed the engine oil was leaking through the filter and was worried incase if there was exceesive pressure built up? My mechanic is somewhat confused as new problems seemes to surface up and I thought I can provide him a checklist to make sure he verifies it and get potential issues sorted out incase if he has inadvertently goofed up.
Back Expand Un-Read 0 Moderator

Reply By: DiscoTourer - Thursday, Sep 05, 2013 at 23:52

Thursday, Sep 05, 2013 at 23:52
Many years back in Karratha I had a friend with a older style Landcruiser (excuse my ignorance for early Toyota models) like Roothys, and the head was put on the wrong way around. I thought he was having a lend of me, but apparently it was possible according to his mechanic. It caused noise and oil leaks. Once it was put on the right way, he was good.

I hope you work out what is wrong.

Brett....
AnswerID: 517708

Follow Up By: Ross M - Friday, Sep 06, 2013 at 08:45

Friday, Sep 06, 2013 at 08:45
DiscoTourer
I am interested to know what engine it was which can have it's head on the wrong way around, it is possible on early Victa mowers and some two stroke bikes, makes no difference for them.
At the moment, I do not know of any car engine or diesel engine which can have the head fitted back to front.
Can't imagine any Toyota engine being reversible.
It is possible to learn something new each day they say.

Ross M
0
FollowupID: 797447

Follow Up By: DiscoTourer - Friday, Sep 06, 2013 at 10:08

Friday, Sep 06, 2013 at 10:08
Hi Ross,

Just spoke with him....it was the head gasket.....20 years had gone by doh!.

It was an FJ40 1982 4.2litre 2F motor (a petrol one....but I guess you would know that). It was rebuilt, and he drove about 2000kms, before he had head issues....but was a little noisy to start with but the Karratha mechanic told him this was normal.

Broome mechanic realised the issue. It was actually the head gasket was installed up side down causing the oil lines in the head not to match up.

Karratha mechanic copped it on his return and ended up paying the Broome mechanic.

Brett....
0
FollowupID: 797453

Follow Up By: Batt's - Friday, Sep 06, 2013 at 11:10

Friday, Sep 06, 2013 at 11:10
I had the same thing head gasket on the wrong way on a 2F which I bought as a rebuilt motor apparently blocks the oil flow I got 400km before it made a noise.
0
FollowupID: 797456

Follow Up By: Ron N - Friday, Sep 06, 2013 at 13:28

Friday, Sep 06, 2013 at 13:28
It's not uncommon to be able to fit a lot of head gaskets the wrong way around.
I just bought a fully reconditioned Nissan A14 engine for a mates Bobcat from a young bloke in Sydney.
Mate installed it, started it up, and it ran hot.
Pulled the head and found the head gasket on the wrong way around.
This reconditioning was reputedly done by a qualified mechanic.
Engine rebuilds must be done with exceptional care and attention to detail.
0
FollowupID: 797459

Reply By: bluefella - Friday, Sep 06, 2013 at 07:48

Friday, Sep 06, 2013 at 07:48
May sound silly but check the exhaust for leak in the engine bay. After engine replacement maybe the manifold hasn't seated properly to the exhaust pipe flange. I have seen this before.


AnswerID: 517712

Reply By: tojofixa - Friday, Sep 06, 2013 at 09:20

Friday, Sep 06, 2013 at 09:20
It sounds to me that you may have insufficient deck clearance on one or more of the pistons. This sometimes happens when new pistons are installed and the deck clearance not checked.
The fix entales removing the head and measuring the height the pistons protrude above the top of the block, and then machining the tops of the pistons to get the required clearance.
Your mechanic may have also assembled the motor with a thinner head gasket than what is required, (I think these motors had graded head gaskets) and it may be as simple as installing a thicker head gasket.
Hope this helps.
Derek
AnswerID: 517719

Follow Up By: Ron N - Friday, Sep 06, 2013 at 13:37

Friday, Sep 06, 2013 at 13:37
I reckon Derek is on the ball. Engine overhaul should involve checking every specification that the manufacturer supplies for the engine.
Many mechanics don't check specifications on overhaul, they presume every part is O.K.

There not only specifications for piston-to-head clearance, as Derek mentions - there are often specifications for conrod twist, conrod straightness, crankshaft twist, crankshaft runout, flywheel runout - and a dozen other items than can seriously affect performance if not checked upon overhaul.

If you can acquire a mechanics stethoscope, you can often pin down the fairly precise location of a noise in the engine.
Deep noises are usually bottom end - lighter noises such as tapping are usually valve train noises, broken ring, or piston contact with the head.

Once you have defined the area where the noise is, disassembly is on the cards.
The fact that the noise comes in at high RPM certainly seems to indicate the piston touching the head.
0
FollowupID: 797460

Reply By: Naveed Merchant - Friday, Sep 06, 2013 at 10:54

Friday, Sep 06, 2013 at 10:54
It sounds more like a bottom end knock .... with oil leaking from the oil filter

AnswerID: 517725

Follow Up By: Batt's - Friday, Sep 06, 2013 at 11:12

Friday, Sep 06, 2013 at 11:12
Take it to a qualified diesel mechanic
0
FollowupID: 797457

Reply By: Member - Alastair D (NSW) - Friday, Sep 06, 2013 at 16:47

Friday, Sep 06, 2013 at 16:47
Assuming new rings were fitted, was the wear ridge at the top of the cylinder removed? If not this will usually cause the top ring to break and causes lots of rattle type noises and poor perfomance including blow pass which might fit with the oil appearance. Saw this on a friends car that was rebuilt by a 'specialist' engine refurbisher. Check if the crankcase breather is showing oil build up.

Hope it is just your imagination but it sounds not.

cheers
AnswerID: 517738

Follow Up By: Naveed Merchant - Friday, Sep 06, 2013 at 17:58

Friday, Sep 06, 2013 at 17:58
The mechanic was able to fix the oil leak today from oil filter due to faulty seal....

the top noise seems OK and good... its just the bottom tap sound thats getting me worried as dont want to get stranded with family during my offroading trips ..

i have uploaded its sound in one of the post here...
0
FollowupID: 797470

Reply By: Naveed Merchant - Friday, Sep 06, 2013 at 17:23

Friday, Sep 06, 2013 at 17:23
I have made recording of the engine sound as per below link from mobile handset by placing it on the upper floor of car interior near the manual gear in between the 2 front seats and this sound becomes more prominent once engine reaches say around 2000 RPM and more on any gear mainly on 1st and 2nd gear and even on idle . The somewhat bottom "tap-tap" sound can be heard more prominently after 40 seconds on https://soundcloud.com/naveed-ahmed-25/12ht-engine-sound

AnswerID: 517739

Reply By: Lyn W3 - Friday, Sep 06, 2013 at 18:33

Friday, Sep 06, 2013 at 18:33
What did the overhaul include?

Did it include an overbore, new pistons, crank grind etc or just a hone, new rings and bearings?

If thats the sound inside the cab it must be pretty loud under the bonnet and you should be able to tell if it is bottom or top end.

Either way it doesn't sound good.
AnswerID: 517744

Follow Up By: Naveed Merchant - Friday, Sep 06, 2013 at 19:05

Friday, Sep 06, 2013 at 19:05
I had first purchased as overhauled engine but it went bust due to faulty fuel pump and even at that time there was this similar tap tap sound from bottom but it was more louder and i think it was the sound of main bearing.

The mechanic changed its main bearing, rings, connecting rods, camshaft bush, camshaft, did oil pump overhaul and lathe machining. Its pistons were fine from the last overhaul

Any ideas what could this be?
0
FollowupID: 797473

Reply By: Axle - Friday, Sep 06, 2013 at 19:24

Friday, Sep 06, 2013 at 19:24
G/Day Mate, ... If it was bottom end noise, i would think all bearings where worn out when it makes a racket like that with revs up, However they have been replaced, so me thinks it sounds like a pump timing ....valve timing issue somewhere! have heard it before....Hope all works out


Cheers Axle.
AnswerID: 517749

Reply By: Shaker - Friday, Sep 06, 2013 at 21:37

Friday, Sep 06, 2013 at 21:37
Not sure if they have them, but could be a loose cylinder liner.

AnswerID: 517757

Reply By: mike39 - Saturday, Sep 07, 2013 at 08:14

Saturday, Sep 07, 2013 at 08:14
Sounds very much like big end bearings to me.
How much oil pressure (ie where does the needle point at around 2500 rpm?)
When driving at around 50kph put your foot down to accelerate. If the noise diminishes then becomes more noticeable as you lift your foot to slow down and continues during the over run then loose big end bearings will be the problem.
Was the crankshaft miked for out of round, were correct size bearing shells fitted (crank may have been ground?)
The 12ht is a strong engine, quite basic in design with a usually trouble free bottom end.
It is possible the piston/con rod assembly has been installed the wrong way round.
mike
AnswerID: 517763

Follow Up By: Naveed Merchant - Saturday, Sep 07, 2013 at 18:17

Saturday, Sep 07, 2013 at 18:17
Oil pressure needle goes at almost full F on the top on 2000 RPM. On 50 km/hr speed i did notice the main bearing sound diminishing on full acceleration and when i released the pedal the sound was there, however oil pressure remained at full.. whereas on idle it comes down to say around 25%.. my mechanic says if main bearings were loose the oil pressure wouldn't be there.

he thinks its probably the fuel pump injection timing ....

I will also ask him to relook at the installation of piston/con rod assembly incase if he has installed the wrong way round
0
FollowupID: 797511

Reply By: Member - Frank P (NSW) - Saturday, Sep 07, 2013 at 09:09

Saturday, Sep 07, 2013 at 09:09
Does that engine have standard oversized or undersized bottom end bearing shells to adapt to production tolerances on the crankshaft?

I overhauled a VH Commodore engine once and fell into that trap. Didn't know about it, bought and installed the wrong shells and had a noisy engine with low oil pressure until corrected.

Cheers
FrankP

Lifetime Member
My Profile  My Blog  My Position  Send Message
Moderator

AnswerID: 517765

Reply By: Naveed Merchant - Saturday, Sep 07, 2013 at 13:28

Saturday, Sep 07, 2013 at 13:28
Thanks for all the feedback... I will go through all the suggested checklist with mechanic today ... hopefully i will be able to resolve this
AnswerID: 517772

Reply By: Tim HJ61 (WA) - Saturday, Sep 07, 2013 at 13:47

Saturday, Sep 07, 2013 at 13:47
I think it sounds pretty normal.

The quality of the sound diminishes when the engine is at speed so makes it hard to hear specific noises. At idle, the engine sounds normal.

It is important to have resolved that oil filter leak, and it is good that the knock seems to be less than before.

A well worn 12h-t, such as over 350,000km, can break a ring and a bit can sit on top of the piston and make a tak tak sound. But this is not relevant to you.

Let us know what you find is the solution.

Tim

AnswerID: 517774

Follow Up By: Naveed Merchant - Saturday, Sep 07, 2013 at 18:29

Saturday, Sep 07, 2013 at 18:29
Tim .. my concern was mainly related to the tak tak sound which can be heard after 40 secs of recording.. and this sound gets more clearer when i release acceleration on 50km/hr (haven't made recording of that as yet)

Whats your gut feel? based on my above feedback and the recording you heard.. do you think its ok?
0
FollowupID: 797512

Reply By: Tim HJ61 (WA) - Saturday, Sep 07, 2013 at 18:54

Saturday, Sep 07, 2013 at 18:54
Naveed

I have made a short recording of my engine, running on biodiesel so it may be little quieter than running on full diesel.

I placed my iPhone about 150mm from my injection pump with the microphone pointing towards the engine.

This is what it sounded like
https://www.dropbox.com/s/c7oqfefkd2abgcs/07_09_2013_4_40_43_PM_2000014.WAV

It's done 260,000km

Maybe you do the same and compare the noise.

Tim
AnswerID: 517785

Follow Up By: Naveed Merchant - Friday, Sep 20, 2013 at 12:38

Friday, Sep 20, 2013 at 12:38
Tim

I compared it with your recording which i assume was taken while your car was in neutral, whereas mine was taken while it was running on 2nd and 3rd gear over 2000 RPM and i noticed the bottom "tap-tap" sound which can be heard more prominently after 40 seconds on https://soundcloud.com/naveed-ahmed-25/12ht-engine-sound ... i didnt note the bottom tap tap sound in your recording.

i am planning to spend some time with mechanic this saturday and hop he is able to find the source of problem
0
FollowupID: 798348

Reply By: Tim HJ61 (WA) - Friday, Sep 20, 2013 at 13:06

Friday, Sep 20, 2013 at 13:06
Hi Naveed

Yes. My vehicle was in neutral and I held my iPhone down near the injection pump.

My thoughts are that with you recording from inside the vehicle while on the road, that there are far too many other noises and possibilities, plus sound muffling, to be clear.

A freshly done up engine should run smoothly, quietly and with no shuddering. It is a thing of beauty, not something that should be causing you angst.

Tim
AnswerID: 518490

Sponsored Links

Popular Products (13)