Piston Slap After Oil Change.

[rebuilder86]

Been a while since ive posted on these forums.

My old 4k engine (not in a corolla) is giving me some scary noises and i wanted to consult with my friends to check the sanity of my thoughts before i take action.

 

I recently changed oil and went from a cheap mineral oil at about 10W-30 (at a guess) to a mid price range synthetic 10w-40. The cheap mineral oil worked well, however.....

Since that oil change i am now getting something which sounds to me like piston slap, similar to what i used to get when i owned a subaru outback; notorious for their piston slapping.

in this instance it only happens once the engine has warmed up properly and everything is nice and hot. (including the oil which reduces its viscosity).

I suspect piston slap as a result of slightly worn out old main bearings and probably big end bearings too, which might be letting out the hot, thinned out, slippery, synthetic oil and reducing the pressure so much that it now doesn't have enough pressure to reach the pistons at the volume required to create adequate cushioning and lubrication.

The whole world of mechanics would try to tell me piston slap only occurs when the engine is cold, but what if piston slap is occurring because of lack of lubrication rather than a bore clearance issue??

 

I am also getting a slightly hotter than usual running condition according to the heat gauge, just below red area when going up hills or on a stinking hot day. However I'm not convinced its truly getting hot as when i turn the ignition key off and on again the gauge resets to the middle normal operating range faster than that amount of heat could possibly dissipate. but this could be an indication of improper lubrication of the cylinder walls leading to severe friction and thus heat.

 

anyone have any insight or thoughts that might help my brain think clearer??

[LittleRedSpirit]

Did you overfill it?

[rebuilder86]

no, its spot on, but why would you ask that just out of interest?

[altezzaclub]

How fast are you driving?? Crawling over rocks at walking pace will certainly keep it hotter than a 100kph cruise.

 

Does the oil pressure light flicker at idle?

 

Drop the oil into a clean container and replace it with some cheap stuff and see if that is the difference. You can get Castrol GTX 15W-50 at Supercheap.

[LittleRedSpirit]

I asked about oil level because I once bought a ke that had a wierd knock described by the seller. I checked the oil, and realised the knock was the crank slapping the oil around. Let a litre out and it was perfect. The noise sounded like a wierd ping/knock.

[rebuilder86]

ahh i see.

altezza, i do a lot of driving slowly over rocky mountainous roads nand through rivers to get to the main highway, but indecently it never gives a hot reading when doing so. only when i get to the highway and start pushing it overtaking tricycles and multicabs does it start to get hot.

 

Update:

I just took the radiator out and found every single tube in the radiator clogged with lime haha. SO i put the radiator on the ground and filled it with hydrochloric acid. and flushed it out.

Also, just put in some thick 20w-50 mineral oil and it seems to have stopped banging. the sounds was more like pinging at idle, and only happened once hot.

 

sigh, i guess thta means i have ot drop the sump n do the big ends at some point. I'm getting too old for this shite.

[altezzaclub]

Can you hear them rattle when you start up??

 

I had to do it on the Girls KE70 after we bought it, purely becasue someone had fitted an oil filter with no non-return valve. Every time you turned the motor off the oil would drain back to the sump, and then it would take 5seconds to get oil pressure when you started.

 

The sump job was impossible in the KE70, it was easier to take the motor out and do a head job at the same time. With the head off I scraped all the scale out of the block coolant galleries. It surprised me how two handfuls of rusty flakes could hide in there. I had the crank cleaned and fitted new bearings, but never took the pistons out.

 

Its never run hot since then.

 

You can buy hi-flow thermostats too, so they control temperature when cold as usual, but flow 30% more water when open.

[rebuilder86]

yes i also have an oil filter without a non return valve. At the beginning of the day, i remove the spark plugs and crank the engine over to get things lubed up, it helps a lot.

This thicker oil has definitely helped a lot.