I have a 2002 Toyota Corolla (1zz-fe engine) and recently noticed an important coolant leak, dripping from under the car, apparently from the oil pan. I took a closer look and was able to identify that the coolant is coming from the very bottom of the timing chain cover. It is leaking through one of the bolts, or possibly through the timing chain cover gasket. It is right next to the crankshaft pulley.

I saw posts suggesting to check the water pump. I changed the o-ring but it did not solve the issue.

Does somebody know what could be going wrong?

I am not even sure there should be coolant behind the timing chain cover in the first place. Do I need to replace the timing chain cover gasket, or to first find where this coolant is coming from?


  • Have a look at the first image on this page (sorry, couldn't link to it). Where is the leak? Here's another image, and here is the timing chain cover
    – Zaid
    Commented Dec 19, 2016 at 18:30
  • Thanks. I highlighted on the image where the coolant is leaking from. My timing cover is still in place, I have not seen the inside, but the bold is where I see the coolant leaking from. See the Image: drive.google.com/file/d/0B9eo8fSBvMK_WWNqU2s3dldyVVU/…
    – Florent
    Commented Dec 19, 2016 at 18:56
  • 1
    To make sure you don't damage your engine, check to see if there is any coolant in the oil. With the close proximity of the these components to the oil pan, and a leak being present, it could happen. If there is coolant in the oil, make sure to change it before running the engine.
    – CharlieRB
    Commented Dec 20, 2016 at 13:43
  • Here's is what I did so far: - Changed the water pump o-ring - Re-sealed the timing chain cover The issue is not solved, and at this point I do not know what to check next. Do you know where this leak could come from?
    – Florent
    Commented Jan 3, 2017 at 18:09

2 Answers 2


I think you need to reseal the timing cover

I found several images uploaded in a ZIP by an enterprising Corolla owner.

Here's an image showing the O-ring you replaced next to the water pump/pulley assembly. If that was leaking you would see water dribbling down the front of the timing chain cover.

O-ring & Timing Chain Cover

Here is another image showing how the gasket maker/sealant is to be applied:

Gasket Maker Trace Example

You can see from the image that if the sealant bead breaks anywhere in the vicinity of the water pump, pressurized coolant will make its way towards the bottom of the cover.

  • 1
    Thanks, this is really helpful. I will start by removing the water pump again and re-sealing this area. Crossing my finger that I do not have to remove the whole thing!
    – Florent
    Commented Dec 19, 2016 at 19:35
  • @Florent unfortunately you will have to take off the timing cover to reapply the sealant. The image shows the reverse side of the timing cover
    – Zaid
    Commented Dec 20, 2016 at 3:22

Had the same problem, Coolant going everywhere. changed the plastic thermostat neck, changed the water pump. Still coolant going everywhere. Took the timing chain cover off to reseal and discovered that the chamber inside the motor mount that is bolted thru the timing chain cover has a hole in the top for ventilation I guess. Well over the years it sealed itself off and the chamber filled with water. on a good cold night the forming ice in this chamber expanded and cracked the timing chain cover directly into the water pump area. I consider this a design flaw. Who puts a vent hole in the top of such an area. I will correct this flaw upon assembly.

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