repair question

[florykitty]

when i first start my tr 4 ,cold start ,i have a engine nock ,after car warms up ,the noise dissapear ,any sugestion?Thank you

[dlb]

could be piston slap. it's commonly heard when cold and then is less noticeable as the engine warms up. i'm not sure how to definitively diagnose it though. in the case of piston slap, i think it's best to do a rebuild (including new pistons) before the piston skirt fails and possibly destroys the block. or you could just live with it till the engine fails and then swap in a known good one.

here's a good description of piston slap i found a while ago:

Piston slap is nothing new to piston driven internal combustion engines and compressors. It is the secondary (sideways or perpendicular) movement of a piston against the side of a cylinder bore where the primary movement of a piston is intended to be parallel (up and down) to the cylinder bore. All piston driven internal combustion engines and compressors have a certain amount of piston slap.

Excessive piston slap occurs when the clearance between the piston and the cylinder bore is too great. The piston to cylinder bore clearance becomes too great either through wear, mismatched pistons and cylinder bores at manufacturing or, a combination of both. The audible noise associated with excessive piston slap is due to the perpendicular impact of the piston against the wall of the cylinder bore. Audible piston slap is typically loudest when the engine is first started up. The pistons then expand with heat reducing the piston to cylinder bore clearance thus, reducing the perpendicular impact of the piston against the cylinder wall and its resulting noise.

[florykitty]

its helpfull ,Thank you DLB

[Petros]

piston slap does not really knock as you get with large bearing clearances. Usually if it was rod knock it will not be noticeable when cold (when the motor oil is cold and thick), but get worse after it warms up, but it would be a hard internal knock. Putting something like STP or other thick additives will reduce that kind of knock. Piston slap is more of a soft "clack" kind of noise, and the STP or similar will also reduce the slap since it will better fill the excessive space between the piston skirt and cylinder wall.

And there are other things that can a knock. bad fuel pumps can knock, as is bad valve train parts. I have also seen a broken tip of a spark plug cause a knock sound when it gets stuck between the piston and head where the clearance is small. If it has a chain drive for the cam shaft, a worn chain will be long and sloppy, and will make a loose chain kind of knock until the oil pressure comes up. most cars have an adjustment if you take off the front cover to take up the slack of a worn chain. if too worn the chain should be replaced.

Good luck.

[florykitty]

Thank you Petros

[Petros]

are you referring to a Tercel4wd as the "tr 4", or is this another type of car? the only TR-4 I know is the Triumph TR-4 sports car, a four cylinder convertible made in the sixties and early 70'ss, replaced by the six cylinder TR-6 later.

[florykitty]

no,my 83 Tercel sr5,i also have 76 mgb but runs perfect,Thanks.i got to projects Petros,try my 83 Tercel from Ashland oregon make a good-perfect runner,and i have to put back together on 85 sr5 Tercel the transmission and good diff that i got from gottolovem,until summer.But i like The one from 83 beter,probably cause is got the inclinometer ,sunroof,try to be my Daily Driving,any advice about oil change.i usualy run sintetique in my all toys,what type for Tercel?10w-30,5w-30,and how many qurts?i also gon put a quart of duralube i think ,probably take some off that nock out when cold start

[Petros]

I do not think I would use 5w-30 in a high mileage engine, but stick with 10w-30. I have recently tried synthic blend 5w-20 in my recently rebuilt 4ac, oil pressure actually appears to have improved, and runs smooth and quit. it seems my fuel economy has improved a bit too.

[Gottolovem]

I run synthetic In all my cars
Back when i was a kid my familly spent a year traveling the us in a large motorhome my father changed to mobil 1 synthetic and improved fuel economy 8%

[florykitty]

i will do that ,Thanks much Petros.Gottolovem-everyone here for help,i run sintetique in my all cars ,it s not gon hurt anything,and sintetique oil becomes cheep ,special here in USA,in Europe they pay $8 box per gal of gas and double for oil ,so

[irowiki]

I would run synthetic in mine but one burns and the other leaks!

[Petros]

if you go through oil that fast there is no point in using costly oil, just use the cheapest stuff you can find.

If the consumption is that bad it might be worth looking for a new motor, or take one of the parts cars you have and rebuild the engine and swap it out one weekend.

[irowiki]

Yeah, I'm thinking of trying to start up the 87 we just got with 277k on the clock and see how the engine runs. Or at least do a compression test.