Jump to content

Probably a standard knock thread


The hatch
 Share

Recommended Posts

Hi folks I need some experience.

The story so far is i was having over heating issues so changed thermostat, then changed water pump etc and eventually turned out the head gaskets went. So had that sorted and skimmed. About 1000 miles maybe less later I started up and then smoke was coming into the cab through the vents so I checked the oil which wasn't showing on the dipstick but wasn't dry (took under 2ltrs) then no issue. 100 miles later ive now got a ticking noise only starting at 2/2.5k revs. My question is does anyone have any ideas where to start checking/whats the issue and also any ideas why it used so much oil? (No oil leaks anywhere).

Appreciate any input good or bad. 

Link to comment
Share on other sites


Many years ago I had oil pipe leak that unfortunately lead to big-end going. Early signs were a ticking type noise under load which over the next few months got worse and evolved into a loud rattle and finally engine seized.

Don't intend to alarm you but given your low oil it may be worth investigating to at least rule it out. Quick redneck check you could hold long screwdriver to top of engine block while engine running and press your ear against the handle and you would be able to hear any unusual noise (ticking, rumble etc). Of course there may be some non related noises but if nothing stands out then that is likely a good sign.

If temperature related, the ticking is more likely not rev dependent and would be heard as components cool down, particularly around the headers and heatshields.

 

Hope it turns out favourably.

Link to comment
Share on other sites

Thanks for your replies. Its is a tinny noise, louder than the usual ticking noise but nothing like what i've saw on videos of knock. Think I'll get a compression test done to see if the oils went by a piston. If it was a bearing that was away I would have thought it would tick on idle and as it revs. The temps are sitting spot on since the heads were sorted but there must have been an underlying issue to make them go. 

Link to comment
Share on other sites

Yeah that is the main issue but also need to find out where the oil was lost from because theres no leaks anywhere. Already spoke to subaru and they said they would do the checks to see where the oil was lost from to cause the issue. Just looking to see what yous guys have experience with the same problems.

Link to comment
Share on other sites

Do you have a oil pressure gauge fitted , if so what's the hot idle in bar ?

If the crank bearings are on the way out it will probably have lower oil pressure.  My old v7sti had a crank rumble , I rebuilt it before it let go but oil pressure was at 1 bar hot idle and you could hear a feint rumbling between 1.5k to 2.5k when blipping the throttle. 

Other tell tale signs where the metal flakes in the sump .

Did you do the h.g yourself,  if not maybe send the builder a video and see what they say .

Link to comment
Share on other sites

I will get a video tomorrow hopefully. It went back to him after using the oil and he said its bearing failure and needs a new short short block and most things oil related (pump, sump, lines etc) he never drained it or anything and is going on his experience I think but first thing I thought would be a compression and leak down test to see where the problem started. 

Link to comment
Share on other sites

I wouldn't rely on the app for oil pressure or knock readings , it was more to see if youd noticed a general drop in hot idle oil pressure. 

Knock is generally either big end or main bearing,  more crank orientated rather than rings .

So a leakdown and compression test would help diagnose if its piston slap , valve seat or maybe early ringland failure but not crank bearings or rod knock tbh . 

Link to comment
Share on other sites

The compression/leak down test is more so to find out where or why the oil went so low in only 1000 ish miles. The lack of oil I'm guessing will be why the bearings have failed which I'll put my hands up for not checking it but after 1000 miles on new oil after the work was done surely means theres a problem somewhere else. 

Link to comment
Share on other sites

If the bearings have failed due to low oil then it must have burnt a hel of alot in that time. Also the bearing failure is just an outcome, not the rot cause of the issue.

1L per 1000 miles is subarus official concern point, but Thats higher than most tuners will accept as being ok. If yours has done 2L in 1000 miles then something is serious wrong.

  • Like 1
Link to comment
Share on other sites

any traces of oil between the engine and gearbox? if there is the rear main seal has gone...alot of people fail to check this and think its engine oil being splashed back from other places which are leaking...oil pressure gauge is a must as its first indication of a problem and not waiting for a light to come on,by that time engine is shot,had it,knackard

  • Like 1
Link to comment
Share on other sites

That's what gave my old v7sti crank rumble @nictriumph👍.

The rear seal leaking pressure but not much oil , dropped the oil pressure down 0.8 bar on hot idle.  The previous owner didn't notice as he didn't do many miles . 

Think you'd have seen smoke outta the tail pipe and cold start piston slap, if the rings were bad enough to use 2ltrs in 1k miles .

Subaru's don't tend to burn much oil through stem seals due to the flat opposing layout . If the bottom end hadn't been rebuilt after the headgaskets were replaced ?

It's a possibility that the initial damage was done by overheating ,burning excessive coolant or pressuring the coolant system with combustion gasses. That could cause a bearing to pinch but the loss of oil would suggest its run low enough for the oil pick up tube not to feed the oil pump .

Oil leak and low oil could easily cause crank failure and if the compression is low,wear rings too .

I'm sure you'll find out once the teardown is done , are you having it rebuilt to stock spec or fitting forged pistons and stopper headgaskets?

Either way best of luck and keep us posted 

Link to comment
Share on other sites

It went back in once I found the oil because there was smoke piling in through the vents into the cab and coming from behind the timing cover. Hopefully next week I can get a second opinion on what's happened. Can't upload the video being the wrong format and can't convert it somehow. I'll try get under and see if there's anything back there. Had a good look about and can't see any visible leaks so its either back there or internal some where.

Link to comment
Share on other sites

Also one of the belts are sqealing really loud which never happened before and when I had the corner of the timing cover off it was like a misting of oil behind it. But the garage said they looked and there was nothing at all behind it.  

Link to comment
Share on other sites

  • 2 weeks later...
  • 1 month later...

Just an update it was the main bearings that went so I have now got a new short block fitted and all oil route (pump, cooler lines etc) replaced. Currently on run in miles just now. Never actually had it stripped down so hopefully the new block lasts plenty of miles this time. 

  • Like 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share






×
×
  • Create New...




Forums


News


Membership