hearing a knock when engine is revved upto 2500 rpms

kfcmgr
0

Asked by kfcmgr Feb 20, 2013 at 02:37 PM about the 1994 Subaru Legacy 4 Dr L Wagon

Question type: Maintenance & Repair

10 Answers

tenspeed
63,785

That's never good. Rod knock? Does the knock go away above 2.5K?

1 out of 1 people think this is helpful.
Derek Dilts
135

Knocking isn't a good thing. How fast is the knock, and does it get faster as RPMs increase? If the knock is more of a "tick" that's really fast, it's likely in the valve train. If it's slower and more "low pitched", it's probably rod knock.

2 out of 2 people think this is helpful.
Jeff Smith
1,535

It could also be piston slap on cold starts. Does it go away once the car warms up?

3 out of 3 people think this is helpful.
John Sturman
1,525

youve also forgot about the shells on the bottom end as theese wear if the car has been thrashed hard on a regular basis

Jeff Smith
1,535

John, what 'shells' are you talking about?

John Sturman
1,525

on the crank shaft there is a series of shell bearings normally made of phosfer bronze if theese wear you will hear a knocking sound when under load as the crank will vibrate and start causing damage to the crank itself to get access to theese you will need to drop the sump/oil pan and then undo the crankshaft this will give you access to the shells. if you can read a micromiter then mic up the shells to work out how much wear there is and replace them accordingly with new shells to correct tolerances and dont forget to replace the oil seals at the same time you will have a rebuilt bottom end which will last quite sometime you can also drop out the pistons from the bottom end if you wish and replace the rings with a set of cords piston rings which hone out the bore and clean it up but you would have to run in the engine for at least a thousand miles drop the engine oil and replace with a good quality oil after this and it would be as if it was a new engine

1 out of 1 people think this is helpful.
Jeff Smith
1,535

What you are recommending then is a full rebuild. The block must be split to replace those rod bearings.

1 out of 1 people think this is helpful.
John Sturman
1,525

a rebuild is the best option as a second hand motor would cost more with fitting than you rebuilding the bottom end

1 out of 1 people think this is helpful.
tenspeed
63,785

Rod knock is a result of the "shells" or rod bearings being worn out. The noise is only heard when the gas pedal is pressed. --- Sometimes engines will make noise from pistons with short skirts. They will rattle a bit until the engine warms up and the piston expands to fill the bore. Pontiac 3100 and 3400 engines do that.

Jeff Smith
1,535

In the Subaru world, this is referred to as piston slap. It's very common on the higher mileage EJ engines.

Your Answer

Add photo

Related Questions

Legacy
Looking for a Used Legacy in your area?
CarGurus has 8,681 nationwide Legacy listings starting at $1,621.
ZIP:

Search Subaru Legacy Questions

Subaru Legacy Experts

#1 Nick Eidemiller
Nick Eidemiller
Reputation 530
#2 dandyoun
dandyoun
Reputation 330
#3 Tom Hawkins
Tom Hawkins
Reputation 270
View All

Related Models For Sale

Used Subaru Impreza"
207 Great Deals out of 10,475 listings starting at $1,950
Used Honda Accord"
1,157 Great Deals out of 61,709 listings starting at $900
Used Toyota Camry"
1,516 Great Deals out of 78,431 listings starting at $1,200
Used Honda Civic"
1,042 Great Deals out of 64,862 listings starting at $1,599
Used Nissan Altima"
1,323 Great Deals out of 84,086 listings starting at $1,495
Used Acura TL"
296 Great Deals out of 5,915 listings starting at $2,000
Used BMW 3 Series"
1,384 Great Deals out of 35,174 listings starting at $1,000

Used Cars For Sale