Something leaking in car

Er Rizwan Patel

Asked by May 18, 2015 at 12:02 PM about the 1998 Toyota Corolla LE

Question type: Maintenance & Repair

I had replaced my gasket few days back and this codes are showing up in OBD reader don't know why and if it is serious? There is something leaking in car

P0302 - Cylinder 2 Misfire Detected
P0304 - Cylinder 4 Misfire Detected
P0303 - Cylinder 3 Misfire Detected
P0135 - O2 Sensor Heater Circuit Bank 1 Sensor 1
P0300 - Random/Multiple Cylinder Misfire Detected
P0420 - Catalyst System Efficiency Below Threshold Bank 1

11 Answers


What makes you say something is leaking? Puddles or visible fluids? If so please describe. Where, color of fluid. None of those codes have anything to do with a leak. Misfires on cylinders can be caused by a multitude of things, and especially the P0300. Do you have the 1.8L?


The P0135 is not necessarily a bad o2 sensor. It's a heated sensor and the code is almost self-explanatory, the heating circuit to it. The P0420 MAYBE is a bad cat, but cats are damaged by lean running, and a vacuum leak, working backwards vacuum leak= lean= ruined cat after a period of time

Er Rizwan Patel

yes i have 1.8L and i can see few drops on the ground and under the hood its look like something is leaking one of my friend said its because of Head gasket can it really be the issue?

2 out of 2 people think this is helpful.

Possibly. But let's not jump too far ahead What gasket did you replace?

Er Rizwan Patel

i had replaced head gasket and spark plugs 3 months back and color of liquid is not sure but it looks like yellowish but leak is not much little i had into minor accident 2 days back was hitted on front right slightly no outer damage

1 out of 1 people think this is helpful.

ok, more questions. Is it-was it-- overheating, before and/or after head gasket job? How does the motor oil look? Have you done a compression check?

1 out of 1 people think this is helpful.

And ignore the bank 1 stuff. It only has one bank

Er Rizwan Patel

no over heating car is driving smooth no such issues while driving, heating and AC also works good only when i put fan on or ac it gives some scratching noise some time other than that car is working well it consumes more oil usually i have to do oil change in 2000-2500 miles and other thing i'm worried is there is something leaking

1 out of 1 people think this is helpful.

Hopefully when the head was off it was sent out for a magnaflux at least, to check for cracks in head, and maybe even milled just SLIGHTLY, and a valve job. Sure, it cost more but is money well spent. Since the car is running well, and not overheating, if the fluid leak is small I really wouldn't worry about it. But if your motor oil begins to look like chocolate milk, or if you see bubbles in radiator while running (don't pop a hot cap), do a compression check. If none of those things happen, I wouldn't be too concerned. Look around for obvious vacuum leaks, like a hose off. If you find one, that is probably the main problem

Er Rizwan Patel

ok thanks for reply


I forgot, if it is blowing white/blue tint smoke from tail pipe, DO the compression check

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