tapping noise on 12ht

[blis]

i will have the compression check, what about the fact that the engine have over 400 km on it, i am concern about reliability, but i also want to save that money. thx

400 000km on 12ht is no worries if the engine works ok, it isnt that uncommon to get good 500 000km-600 000km on them without need for engine overhaul...

 

[roscoFJ73]

i will have the compression check, what about the fact that the engine have over 400 km on it, i am concern about reliability, but i also want to save that money. thx

Try the 20-50 as well

Its unlikely it will die quickly,you normally get a decade or so warning with a 12HT

 

[rideglobally]

blow by?

Thanks blis and Roscoe,
what about the amount of blow by, at what point do i start worrying about that?

it cost 5 to 6 thousand dollars to overall an engine here in los angeles, ca. that include taking out of the engine bay and putting it back after the overall.

Try the 20-50 as well

Its unlikely it will die quickly,you normally get a decade or so warning with a 12HT

 

[roscoFJ73]

Thanks blis and Roscoe,
what about the amount of blow by, at what point do i start worrying about that?

it cost 5 to 6 thousand dollars to overall an engine here in los angeles, ca. that include taking out of the engine bay and putting it back after the overall.

How much blowby do you have? Try the thicker oil ,it may help.

$5-6k is cheap if they are installing it. The 12HT needs a good rebuilder so I would be wary of taking it to someone who has not done one before

 

[maxigaz]

hello forum,
this is my first post. I like the 12 ht so i couldn't resist to add my little comment.
I have rebuilt a few 12 ht, and like the australian felow said, the weak spot of those engines are the piston.
there is a company in perth australia selling pistons with the steel insert, these are called alfin inserts.
The ones i got from perth were made in japan , i know of a turkish company ,part of the mahle group ,making some for the 12 ht.
i also found quite a few rod bearing shells that had a very strange erosion, and that produced a constant little pinging.
i since use only ACL trimetal bearings .
cheers
stef

 

[bigbrowndog]

Cheers, The pistons I bought were from Precision International [Hypatic Pistons] and I believe this company is in the U.S.A. also.
I find it hard to believe the 12HT needs rebuilding at 400,000 Ks unless it has been abused like run very low on oil or overheated. The oil squirter's usually keep the 12HT pistons better than a 2H Turbo motor also. Rattling and knocking in the 2H is nothing to worry about but the 12HT is usually quieter and not as Mack truck sounding as the 2H. When you checked the valve clearance did you inspect the rocker arm as once the hard facing wears the face soon becomes concave where it contacts the pushrod thus being outside the setting when the feeler gauge is inserted and contacts the unworn face and the top of the pushrod. Do the rocker arms need refacing at all? As others have said the 2H/12HT should be run on 20.50 oil after 120,000Ks in warm to hot places. That is what is recommended here.Check none of your injector bodies are broken or loose. Check all the easy obvious things first. If you want a picture of the pistons I will dig one up. Goodluck.

 

[Garry]

When were the injectors last serviced? A dodgy injector can cause the odd strange noise Also, could be a worn valve guide or two? (my 2 cents)

 

[prado t]

Hi guys , My 12H-T has a ticking noise also ; went over everything and came to the conclusion that the clutch may have a loose spring ., tick,tick,tick,tick at idle . When I step on the clutch it goes away. Even High idle it is consistant with RPMs

 

[Stephen835259]

Sorry, I realize it's been a while. How did the lifters look when they were pulled at 400km? Any idea what was causing the tapping noise?

 

[relaxedcruiser]

Hi guys, again a while since the last post...
just want to mention that I got rid of a tapping noise when I re-ground my rockers where they meet the valves. Some of them were quite badly worn. And because of that "hole" the valve stem has worked into the rocker you are not able to set your valve clearances correct, you´ll always have to much of a clearance - giving you that annoying sound. I´ll now have a look at them again as I want to replace the lifters on which had found cracks and pitting when I had the head off couple of months ago. I´m curious to see how the reground faces look now. I´m well aware that I ground away the hardened surface on them, but this was already gone anyway where the valve stem has done its own milling job....

 

[Greystroke]

Be interested to see how the non hardened faces hold up over time. Might be something to look at on my old girl as she's doing something very similar. Think I would get them refaced though.

 

[relaxedcruiser]

Hi Greysroke,

I´m sorry to say that I have postponed the lifter replacement for at least 8 weeks as I´m travelling overseas - back to good old Germany where I´m originally from. Will report after returning ...Happy cruising !

 

[Fred12HT]

Howdy anyone that may still be in tune with this thread!
1988, 12HT, been running well the past 4 years i've had it, had the injectors overhauled 18 months ago with a reputable firm, never an out of touch noise until 2 months ago, randomly started tapping on top end around cylinder one, not noticeable on idle but under power and revs it was crazy loud. I immediately parked it up till i could sort it out. Did an oil change, nothing out of normal using Penrite 15-50 semi synthetic extra ten, full zinc oil. No change.
Since then I checked and set valve clearances, no change. Lifting push rods, i found the C1 exhaust rod and lifter (call this lifter L2) made a catching/flicking sound on lifting and depressing where all others were smooth. So I stripped that side of the motor, push rod panels off, and upon simply removing L2, inspecting and reinserting it wasn't catching anymore! Nevertheless i checked all lifters, inspected the cam shaft and rotated to see if i could notice any wear or scoring etc, nothing obvious. Cleaned everything up, some light emery paper on a few stickier lifters and the main question mark L2, reinserted with moly paste etc etc.
Fitted valve train, adjusted everything, fired up, little to no noise but not much revving and warmed it up. Fired up again today to build to temp and similar noise came back. Once warm, checked and adjusted all valves again with very snug feeler gauge fit. Ran up and still getting the same noise. Not as bad as when it first started but not gone and i suspect under driving will be back!

I do have a snapped exhaust stud on the bottom side of the front of the manifold but this happened 18months ago which i never replaced, wondering if this could be the source of an exhaust knock or is that only from a valve? Can an exhaust knock literally come from an unsealed part of exhaust manifold?

I don't know the condition of the pistons but suspect no rebuild and original pistons.

Any other ideas??

Thanks for anyone who may be listening!