my 97 honda civic HX with 99K recently developed a knock upon start up on cold mornings. They said its piston knock and its nothing to worry about.... are they feeding me a line or what?

 

Good choice on model.

Yup, it's piston slap, common among cold honda engines.

 

so it is common.....ppl tell me i might have a vacuum leak....the knock goes away when the motor is warm though

 

No honda engine I have ever seen with stock pistons has had any piston
slap.

 

in a gangsta voice (true)

 

Hrm, my EX engine does it and it also has 99k on the od.

 

sounds like its getting worn out.

 

FWIW, I'm the original owner of a '90 Civic Si. When I first picked it up, I took it back to the dealer because I detected a faint rattling noise. I was told it was piston slap. The aluminum pistons fit slightly loose in the bore until they heat up. Over the years, when the weather was like zero degrees, the cold engine sounded like a diesel until it warmed up. Anyway, long story short, the original engine has over 241,000 miles on it now and it uses about 6 ounces of oil between 4,000 mile change intervals.

 

Yeah I am gonna rebuild it some day...........Maybe.

 

its normal, my g/f has a bone stock '96civic that does it in the mornings


[Modified by fiebru1119, 11:48 PM 1/30/2002]

 

Not true.
Honda pistons run such tight clearances that it scares most (domestic)machinists.

 

It's realy nothing to worry about, Honda issued a TSB stating that it's normal...not common but again nothing to worry about. Just give your car time to warm up.

 

I've only heard of "piston slap" with forged pistons. That doesn't mean it doesn't happen with stock ones, just letting you know what I've heard.

 

piston slap is common with forged pistons because they have roughly twice the thermal expansion rate as cast slugs. So you have to run a looser piston-to-wall clearance with forged to make them work. Forged pistons are not common on emissions motors because of this, the cold emissions are terrible.
my 91 teg GS has piston slap too, i just let it warm up for 1 min before driving and dont worry too much.

 

warm up the car man

 

I have the same issue too and I do have forged pistons, so yea it must be something with em forged pistons - just let it warm up I guess...

 

Ah f**k its 02 thread - honestly did not see that guys lol

 

i knew sombody that drove for quite a whille with a piston slap