Mechanical question

[cdavis3361]

So I have an 04 DII. When I start it from cold it sounds like an air-raid siren for about 30 sec. Then winds down and is done.

It also pops up occasionally while driving for a few seconds. Very strange, almost sounds like a cooling fan.

What is this?

 

[LtFuzz]

that noise right there is your viscous fan clutch warming up

totally normal

 

[cdavis3361]

Excellent, glad it is not something serious.

So perhaps it is my imagination, but it seems to have gotten louder over the past few months. Would that indicate that it starting to go out? Or don't worry about it?

 

[ZG]

it's also been getting colder the past couple months


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[I Leak Oil]

As said, perfectly normal. My previous coilers have done this and my Chevy silverado does it. Just the way it is.
When it does it all the time or not at all is when you need to worry about it.

 

[LtFuzz]

Excellent, glad it is not something serious.

So perhaps it is my imagination, but it seems to have gotten louder over the past few months. Would that indicate that it starting to go out? Or don't worry about it?

It's probably not necessarily louder, but staying on a bit longer because, as RNPhoto said, it's getting colder -- so it takes longer for it to warm up.

Indications of it failing will be when it's cold and you don't hear it at all on first time startup.

 

[cdavis3361]

Awesome info, it's great that you all are such a resource. Thanks for the feedback

 

[fishEH]

Here's my remedial understanding of how it works. Please correct me where I'm wrong because I'd like to better understand it myself.

The viscous coupling contains a temperature sensitive fluid/oil. When the truck sits that fluid pools on bottom of an inner ring. Because the fluid is pooled the weight distribution is on one side which causes the fan to spin when first started. It spins until that fluid is evenly distributed throughout the inner ring, at which point the fan stops spinning. This part has nothing to do with temperature or being "warmed up", I think.
As the temperature inside the engine bay climbs the fluid warms and thins out. As it does this it works its way to an outer ring. Once there centrifugal force causes the fan to spin. The fan spins until the engine bay temperature drops enough for the fluid to cool and return to the inner ring of the coupler and the fan stops spinning.

What say Ye?

 

[david despain]

did any 03-04 have SAI?

 

[ipgregory]

Here's my remedial understanding of how it works. Please correct me where I'm wrong because I'd like to better understand it myself.

The viscous coupling contains a temperature sensitive fluid/oil. When the truck sits that fluid pools on bottom of an inner ring. Because the fluid is pooled the weight distribution is on one side which causes the fan to spin when first started. It spins until that fluid is evenly distributed throughout the inner ring, at which point the fan stops spinning. This part has nothing to do with temperature or being "warmed up", I think.
As the temperature inside the engine bay climbs the fluid warms and thins out. As it does this it works its way to an outer ring. Once there centrifugal force causes the fan to spin. The fan spins until the engine bay temperature drops enough for the fluid to cool and return to the inner ring of the coupler and the fan stops spinning.

What say Ye?

Probably right on some but on the LR Coilers at least there's a slight difference. The fluid is not heat sensitive, there is a bi-metallic spring on the front of the unit. When the temp changes it turns a valve inside that opens or closes passageways to allow the fluid to move into different areas and lock or unlock the unit. Kind of like a torque converter. The temp comes from the air coming through the radiator. As the rad heats up the air passing through heats up and in turn warms up the spring on the front of the unit changing the path for the fluid inside.

Thats my understanding anyway.

 

[The Rover Shop]

I am gonna say its the SAI (Secoondary Air Injection) blower motor..the black unit in the right hand rear of the engine bay...basically just a big air blower..the bearings go bad in them and they make that noise..next time you start the car cold open the hood first and put your hand on that unit and you will soon know if thats it or not..if any doubt, disconnect the wiring to it and see if it goes away... it MAY flag the check engine light on...

 

[NSGINC]

Rover shop is right. Its your SAI pump. They go bad all the time. Pop your hood in the morning then start it up. Place your hand on the pump. You will feel it run and hear your noise. When you feel it stop and your noise stops. You know. Easy fix, 3 10mm nuts, a connector, and one hose to remove.

 

[brushogger]

Secondary Air Injection pump.


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[baja5337]

I concur with Secondary Air Pump, super common, I wouldn't replace it until it seizes

 

[cdavis3361]

A follow up and confirm my suspicions. So now the air-raid noise has stopped, for the most part. New symptom is the idle is really low, feels like it is going to stall out. Symptom resolves with application of throttle, no problems when driving.
I'm feeling like this pump has finally crapped out & needs to be replaced, engine not getting enough air & all.

Am I on the right track? Way off?

Thanks for the help