Exhaust Blow? Clears After Engine Warms Up - Confused!

[EastLondonGuy]

Hi,

New Rav4 owner; I have a Rav4 Auto 2004 with genuine 46k.

When starting the car, it sounds like there is a blow when auto choke is on and idles at 1300-1600rpm. When engine warms up within 30-45 secs (it's Summer - just about!), car sounds fine. When driving at speed with revs at 2500 to 3500 exhaust still sounds fine.

Is it me or am I going mad??? Pls help.

Cheers!

[gjnorthall]

It's not unusual for an engine / exhaust to sound a little unusual whilst warming up. There are several factors in play including an enriched mixture and tappets which may be a little noisy. However a cracked or loose exhaust manifold can blow when cold but seal as it comes up to running temperature.

[EastLondonGuy]

What can I do to check? Do I get my local bod to put the car on the ramp?

[Madasafish]

I drove a 1953 Rover 75 with the same problem. Leak found by running hand carefully around manifold/exhaust system when engine was cold.. In this case, it was a small hole in the manifold gasket which was nosiy when cold, but partailly closed up when warm - and the noise disappeared.

Nearly killed us through CO posioning..

[Parts-King]

Oh those 1953 Rovers.............

[alan333]

What can I do to check?

Put your hand over the end of the exhaust for a few seconds, temporarily blocking it. You'll hear if any gas is escaping, and you'll feel the build up of pressure releasing when you remove your hand. Remember it'll be hot if the engine has been running, and it'll be dirty, so maybe wear a glove.