Power Loss - EGR or Head?

[rg]

Folks,

My 2.5 seems to have a definite lack of grunt at the moment.

There's much written about stuck EGRs, and I'll follow the procedures to check it. However, I don't get much smoke out the back, and the power loss is not like that of my old Vauxhall Monterey when it's EGR stuck. That seemed like some catastrophic failure, smoke, noise, power loss. It went when I by-passed it.

Can anyone relate any experiences as to how much power is lost when it goes? Also, more worryingly, I have lost a bit of coolant, and there's still some oily grey gunge in the tank, although I've not flushed out since I by-passed the oil cooler, so it may be left over from that. Does head gasket failure/head cracking cause a loss of power? I'm hoping that the loss of coolant may be due to a seeping cap.

Not a happy time for my XM at the moment. It's at 186K, and seems to have a mid-life crisis...

rg

[robertmnorton]

Hi rg, you've certainly dived in at the deep end, as i'm sure you're aware many things can cause loss of power. I only have experience of XUD fuel systems, but have you ruled out any air leaks, disconnected sense lines or connectors, adequate fuel supply ie. filters, tank pickup, air in fuel, correct operation of needle lift and tdc sensor, throttle cable adjustment etc,etc ? A diagnostic run would rule out a lot of this and present any fault codes. A pressure check of the cooling system is easier enough (i have a cap with a schrader valve, use a tyre pressure gauge to monitor) to rule out hg/intercooler, a seeping cap may be due excess pressure caused by hg failure. EGR more difficult but a vacuum (siphon pump) applied to the control line will actuate it and you should hear it open and close. You state, not much smoke, only under load would i expect smoke, and then not much, so the colour of any smoke and under what load conditions help with diagnostics.
Hope someone else can give you a better guide.
robertm

[rg]

Many thanks.

If it's the HG, then this will be adieu XM.

r

[rosspa]

Have you checked the large rubber pipe at the front of the engine fo splits. This pipe from the intercooler to the manifold often splits, usually out of site on the underside. I have had this happen twice. It is accompanied by a substantial loss of power, as the effect is the loss of the turbo. You wont notice it at idle or low revs.

[rg]

Many thanks. I'll take a look.

The scare about the head seems only a scare. I found an intermittent, temperature-related leak from the bypass mod. I did around the oil cooler. This must be the only time I've actually been glad to see a coolant leak...

[nightmare]

Noz did a very good help file on the turbo wastegate sticking.
If it sticks partly open you'll get power loss.

http://club-xm.com/forum/index.php?showtopic=2717

HTH

This post has been edited by nightmare on December 29, 2012 10:40 am

[rg]

Thanks!

As always, this is reassuring.

This will line up behind the other jobs. Driveshaft bearing first, I think.

Was Noz in the New Years Honours List? If not, then why not? :-)