Piston slap or lifter tap???
03-08-2014, 07:46 AM
#1
Piston slap or lifter tap??? Is there a definite way to tell the difference between the two without changing lifters to see if that fixes the problem? I thought my car had piston slap on startup when engine is cold but a LS shop I took it to said its definitely lifters rattling. The engine was understood to be bone stock when I bought the car but the guy I bought it from only had it a short time and didnt know crap about it. 
I have unusually high oil pressure for a high mileage engine IMO. When warm it is 45-50psi at idle with 5W-30 synthetic oil in it. When crusing its 60psi and when at roughly 3500RPM its shown 70PSI at times. It might have different oil pump in it than what was factory but IDK.
I have unusually high oil pressure for a high mileage engine IMO. When warm it is 45-50psi at idle with 5W-30 synthetic oil in it. When crusing its 60psi and when at roughly 3500RPM its shown 70PSI at times. It might have different oil pump in it than what was factory but IDK. Last edited by JRENIGAR; 03-08-2014 at 10:22 AM.
03-08-2014, 08:57 AM
#2
He probably sold it because he thought it was piston slap. From, what I read here, a lot of the lifter tick noise is from a lifter wheel damage. I'd just replace the lifters to be safe.
03-08-2014, 10:20 AM
#4
Yes, it all but goes away and thats why I thought it was piston slap. When it warms up sometimes there is a faint tick that remains but its very light. Shop said it was lifters gummed up and not letting oil flow properly and that is probably why the oil pressure is so high. They told me that on LS1's with high mileage the pressure hot should be 30PSI or so when ideling and that only a Meling pump could make the pressure as high as it is.
03-08-2014, 10:41 AM
#5
Yes, it all but goes away and thats why I thought it was piston slap. When it warms up sometimes there is a faint tick that remains but its very light. Shop said it was lifters gummed up and not letting oil flow properly and that is probably why the oil pressure is so high. They told me that on LS1's with high mileage the pressure hot should be 30PSI or so when ideling and that only a Meling pump could make the pressure as high as it is.
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03-08-2014, 12:03 PM
#12
Piston slap and lifter noise is 2 different worlds apart. Piston slap sounds like a hollow knocking diesel engine noise. Lifters tick and tap<noway you can mistake one for the other.
I wanna tell you what most people hear in these engines cold that completely freaks everyone out.
What you are actually hearing is the carbon on tops of the pistons hitting the cylinder heads. It makes a hell of a lot of noise THAT IS LS1 noise. You can take a NOISY when cold high mileage engine and DECARBON it will be quiet as a mouse.
I had a 99 TA with 135k on it that knocked so bad cold I would CRINGE every time I started it cold. It knocked and knocked and then after about 5 mins it would be quiet but you could still hear a faint diesel noise in the engine.
Dealer mechanic heard it while driving the car and recommended DECARBONING service. I blew him off UNTIL he explained that these aluminum engine GROW ALOT when hot and then shrink when cold then the carbon on the pistons whack the heads until you get some heat in the engine and it grows again.
I had them do and that engine WAS QUIET AS A MOUSE AFTERWARDS!
After listening to that knocking for over 80k miles it was SILENT!
I wanna tell you what most people hear in these engines cold that completely freaks everyone out.
What you are actually hearing is the carbon on tops of the pistons hitting the cylinder heads. It makes a hell of a lot of noise THAT IS LS1 noise. You can take a NOISY when cold high mileage engine and DECARBON it will be quiet as a mouse.
I had a 99 TA with 135k on it that knocked so bad cold I would CRINGE every time I started it cold. It knocked and knocked and then after about 5 mins it would be quiet but you could still hear a faint diesel noise in the engine.
Dealer mechanic heard it while driving the car and recommended DECARBONING service. I blew him off UNTIL he explained that these aluminum engine GROW ALOT when hot and then shrink when cold then the carbon on the pistons whack the heads until you get some heat in the engine and it grows again.
I had them do and that engine WAS QUIET AS A MOUSE AFTERWARDS!
After listening to that knocking for over 80k miles it was SILENT!
03-08-2014, 12:08 PM
#13
That filter bypass is only there to bypass oil IF the filter is blocked OR the oil is too cold to flow through the filter.............it has no effect on the line pressure you see at the gauge.
I wouldn't believe the factory gauge, it could high or low by 5-20 psi. Only way to really know is use a CALIBRATED test gauge.........
I wouldn't believe the factory gauge, it could high or low by 5-20 psi. Only way to really know is use a CALIBRATED test gauge.........
Last edited by RockinWs6; 03-08-2014 at 12:13 PM.
03-08-2014, 02:24 PM
#14
Piston slap and lifter noise is 2 different worlds apart. Piston slap sounds like a hollow knocking diesel engine noise. Lifters tick and tap<noway you can mistake one for the other.
I wanna tell you what most people hear in these engines cold that completely freaks everyone out.
What you are actually hearing is the carbon on tops of the pistons hitting the cylinder heads. It makes a hell of a lot of noise THAT IS LS1 noise. You can take a NOISY when cold high mileage engine and DECARBON it will be quiet as a mouse.
I had a 99 TA with 135k on it that knocked so bad cold I would CRINGE every time I started it cold. It knocked and knocked and then after about 5 mins it would be quiet but you could still hear a faint diesel noise in the engine.
Dealer mechanic heard it while driving the car and recommended DECARBONING service. I blew him off UNTIL he explained that these aluminum engine GROW ALOT when hot and then shrink when cold then the carbon on the pistons whack the heads until you get some heat in the engine and it grows again.
I had them do and that engine WAS QUIET AS A MOUSE AFTERWARDS!
After listening to that knocking for over 80k miles it was SILENT!
I wanna tell you what most people hear in these engines cold that completely freaks everyone out.
What you are actually hearing is the carbon on tops of the pistons hitting the cylinder heads. It makes a hell of a lot of noise THAT IS LS1 noise. You can take a NOISY when cold high mileage engine and DECARBON it will be quiet as a mouse.
I had a 99 TA with 135k on it that knocked so bad cold I would CRINGE every time I started it cold. It knocked and knocked and then after about 5 mins it would be quiet but you could still hear a faint diesel noise in the engine.
Dealer mechanic heard it while driving the car and recommended DECARBONING service. I blew him off UNTIL he explained that these aluminum engine GROW ALOT when hot and then shrink when cold then the carbon on the pistons whack the heads until you get some heat in the engine and it grows again.
I had them do and that engine WAS QUIET AS A MOUSE AFTERWARDS!
After listening to that knocking for over 80k miles it was SILENT!
Last edited by JRENIGAR; 03-08-2014 at 02:44 PM.
03-08-2014, 02:27 PM
#15
That filter bypass is only there to bypass oil IF the filter is blocked OR the oil is too cold to flow through the filter.............it has no effect on the line pressure you see at the gauge.
I wouldn't believe the factory gauge, it could high or low by 5-20 psi. Only way to really know is use a CALIBRATED test gauge.........
I wouldn't believe the factory gauge, it could high or low by 5-20 psi. Only way to really know is use a CALIBRATED test gauge.........
03-08-2014, 03:42 PM
#16
Are you certain about the bypass in that it only flows oil if the filter dosent. I wonder how cold 5W-30 oil has to be to not flow through a filter on startup? This might still be the problem with the rattling at startup when the engine is cold, No? If the guage reads zero when key is on and engine is not running then wouldnt that mean its fairly accurate, atleast at the lower end of the spectrum?
03-08-2014, 04:14 PM
#17
I personally have not made an A/B oil pressure comparison, but the Service Manual (as well as other internet articles) consistently indicate that a blocked oil filter/oil filter bypass valve/oil pressure relief valve results in higher oil pressure readings at the vehicle's gauge (but not a direct connect physical gauge).
03-08-2014, 05:46 PM
#18
i personally have not made an a/b oil pressure comparison, but the service manual (as well as other internet articles) consistently indicate that a blocked oil filter/oil filter bypass valve/oil pressure relief valve results in higher oil pressure readings at the vehicle's gauge (but not a direct connect physical gauge).
03-08-2014, 05:59 PM
#19
The pressure is created by the pump, but is not measured at the pump. It is measured by the sensor located downstream of both the pump and the oil filter loop (which can be either open, and therefore included in the stream, or closed and thereby excluded from the stream.).