Hi again,
So, I don't know that this is a problem, but on cold starts, the engine is pretty loud and sounds almost like a diesel or like it has an exhaust leak. If I let it run for about 30 seconds it seems to lower rpm and get quiet again. If I don't wait and put it in gear, it will also quiet down. I hear the SAI going, but that's pretty quiet and not the source of the racket..unless the SAI system pushing air into the manifolds is kind of loud in general. Once in gear and driving, the truck is quiet. Any one else?

 

between the viscous fan clutch and any noise from your sai, it is going to be a pretty loud roar on cold start up. the goo in the clutch has to wake up and get moving, so fan is full on. in gear you are lowering rpms. unless you are hearing more than that roar (clanging, grinding, rattling, etc) probably normal

 

The symptom of a bad SAI solenoid is a low frequency burble which is actually exhaust backflowing through the SAI valves as the pump is pumping. When the pump is told to pump the solenoid opens the valves which allow the air from the pump to go into the valve covers. If the solenoid fails then the vacuum controlled SAI valves allow exhaust to flow backward through the valve to the pump. Common failure. Cheap fix.

If the noise is jet engine style then that is the bearings in the pump itself.

 

Thanks for the replies. It's definitely a low frequency sound. Is there a way to check the SAI selenoid? I have a feeling that my noise is normal, but wouldn't mind making sure. Thanks again.

 

I just tested and replaced mine.

2 minutes to take off the car. Put 12v across it and it should have a very definite tick as it opens and closes. Mine had a very sloppy broken spring kinda noise.

I also had the CES light on, throwing vacuum codes. Sorted all that out.

 

Cool. Thanks, I'll test it this weekend.

 

Looks like the solenoid is good. Is it possible that a control valve isn't working properly? Do those need to be cleaned ever?

 

I had two Land Rover discovery.
A 1997 and a 2001.

The 1997 did that a lot for the first minute.
Gets worse with miles on the engine.
Sold the D1 at 170,000 miles.

D2 did that too - at 107,000 was getting louder.

I think it is pistons slapping.
When the motor gets hot - the noise calms goes away.

You will notice the clatter happens louder when you give it just a little acceleration.

you may also have a head gasket getting ready to go and it could be leaking a bit.

or you have exhaust manifolds loose or loose exhaust elsewhere.

When you tighten the bolts then the bolts will snap off.
Best to leave this alone and keep driving.

 

A failed pump motor will also cause this sound as the valves open and the pump has no pressure exhaust will go out this way.

check your pump to make sure it is running, pumping, and not clogged with old filter debris.