Cold Start Whine

[Tonyfeb14]

My 2003 X5 4.4 has a cold start whine, that is pretty loud and stops after a few minutes as the engine heats. It is only on cold start. I have researched and found that the timing chain guides are prone to failure on the M62, but I don't know what that sounds like. The timing chain guide issue was described as a grinding sound on one of the DIY videos. My car is more a of high pitched whine that stops after a few minutes. Sounds like a jet turbine, then stops. Any idea what this might be? I am not convinced its is the timing chain guides as that will be a "project" to tear down to replace.

[Boston01X5]

Can you send a short video, of a cold start with hood open, so is easier to diagnose what the problem is?

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[andrewwynn]

if it stops after exactly 90 seconds it's the secondary air pump; bearing shot.

people have pulled them apart to replace the bearings. I just replaced my wife's about a month ago and i took the old one apart for forensic purposes and i could not figure out how to remove the blower off the shaft that you'd need to do to replace the bearings.

we have the 3.0 and the pump is directly behind the right headlight, it will have a filter that goes through a hose to the pump. search for the pump follow the sound after a cold start, the pump is about 5" around at the top with a hose going into it from the filter.

the 'good news' (possibly) is that ours continued to work for over a year from when the jet taking off sound started; the pump is very expensive; $465 at fcpeuro.

I reengineered one that I got from a 7-series; i can share pics how to do that, it greatly expands the options for hand-me-down possibilities.

Find one at a pick n pull yard to save a bunch of $

[andrewwynn]

followup on the chain guides; the sound made from timing chain guide failure people refer to as marbles getting chewed up by the engine. it would not be confused with jet sound, but also; the problem could likely be avoided entirely by regular replacement of the timing chain tensioner with an OEM model; don't use a knock off, they can't be trusted. The tensioner should probably be replaced every 60,000 miles to maintain proper tension on the timing chain; without enough tension the chain will slap onto the PLASTIC chain guides which get brittle and will crack into pieces. It's about $70 for an OEM or OE tensioner. It's about $1000 in parts and 30 hours DIY to replace the timing chain guides. (or $5000 at dealer).

[Boston01X5]

Great advice, Sir Andrew Wynn

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[Overboost]

Definitely sound like the SAP pump. Mine went out and sounded just like a jet engine throttling up for take off.

[andrewwynn]

Post mortem on Lumba2's SAP.

It is an interesting design. It's a stacked set of blowers with aluminium blades. The output of the first goes into the input or the second stage. It has to make more pressure than the exhaust at full RPM.



5 series v X5 SAP. I think BMW went to the external filter so they could have a bigger filter to deal with more dust in off road situations.

The fitment was so tight having the filter attached to the pump I had to cut a notch out of the frame around the headlights as it touched and used the headlight like a megaphone.

[Tonyfeb14]

Thanks everyone. I will check out the pump. Not ready to jump in to replace the timing chain and guides if I can avoid it.

[andrewwynn]

wife's SAP started doing the jet whine about a year before i replaced it, it shouldn't die outright too soon just is very annoying for the first 90 seconds every time it cold starts.. eventually it will stop putting out enough air and you'll get SAP related errors.

[Tonyfeb14]

Circling back on the timing chain, I see the lower timing chain tensioner is externally removable on the 4.4. A genuine BMW unit is about $98 from ECS tuning.

Andrewynn, were you recommending just changing that one tensioner out and that was enough to stave off some timing chain guide problems? I have 140k miles on my X5, and is the SAP is making all the jet noises.

I am also looking at chasing down a coolant leak and that might have been taking the manifold off to replace the galley gaskets, etc. So as long as i have it all apart, maybe this is an easy preventive measure. I just don't like replacing one tensioner if this is only part of the problem. Then replacing one is false sense of security.

Let me know what you think. You have been very helpful so far.