EGR Blank and Valve Failure (she's dead,solved)

[jimmy_jay89]

ok so the word is that the blanking plate that was put in by my usual mod guy was non-existant

in a way that it completly disintegrated into the intake (it was way to thin)

the gasket had also went

on top of this, the butterfly valve in the egr was missing... they dont know if some of it had gone through the intake but it was melted away aswell

this allowed for all exhaust gases to flow through the intake starving the engine

they put a test blank in and the car started first go no worries

they are putting a new larger, heavier blank in to ensure it doesnt happen again

 

[doc]

SWEET! See, nice and easy, and hopefully a labour bill which isn't horrible.

Now....this weekend I'll check my EGR plate...

 

[jimmy_jay89]

labour bill will be bad atleast 8hrs +

 

[nathand22]

what was the original plate made out of? and how thick was it?

 

[jimmy_jay89]

they couldnt say

all they could tell was that it was metal and very very thin

 

[nathand22]

yeah i have read a thread on 4x4earth (i think) where a few guys had used a really thin sheet of mild steel and had it disappear.
I ended up using around 1.5mm thick stainless, hope that is ok??, i used it on my last nav and no probs for at-least the first 110k

 

[Old.Tony]

That's scary.

The temps at that part of the manifold shouldn't be that high. What did they use, foil? Aluminium plate? Jeez.

Mine's made of about 1mm stainless plate. I'll check it soon.

Here's a better question - how did the EGR butterfly valve melt too? What kind of temps had to be in there for it to do that?

I wonder if some post-combustion injection made its way into the EGR tube and ignited once the gas in the tube started flowing? That means two things:

1) It's vital to make sure your EGR blanking plate is thick enough to NOT fail, and

2) It would make sense to try and block the exhaust side with an even thicker (perhaps cast) plate.

Now, this latter one gives me an idea. I might make a plate to fit the exhaust side, and fit that with a thermal probe for measuring EGT.

After the house reno is over - got my hands very, very full at the moment.

 

[doc]

I was wondering Tony - those who have a small hole through their plate could potentially suffer this problem due to the flow of heated gas past the plate.

No hole - the pipe pressurises, but there is no circulation of gas as such.

Hole through plate - there is circulation of gas. But because the hole is small, the hot gasses are forced to remain in the vicinity of the plate for an extended period.

Only a theory...

 

[Old.Tony]

Interesting theory, certainly makes you think. The hole is essential for those with flow sensors. But - in a normally-functioning car, there's no blank plate, so there's even more flow = more potential problem?

Maybe it's a combination of soot buildup + exhaust stroke fuel injection + the creation of the hole. This might mean that those with the (necessary) hole will likely eventually have the problem too?

It's more support for blocking the exhaust side of the EGR tube.

 

[ourd40]

My plate has been in for 35k and checked it last week and other than being a little black no sign of failing

 

[camo.b]

I made mine out of 3mm steel plate but it was a pain to fit it back up due to the extra thickness..but it will last...old tony when I installed my egt probe I used the same place you are thinking I first removed the egr tubing again total pain..and couldn't refit it within 10 mins,got mad so I cut off both ends just before and after the heat exchanger tube.used my blank as a cap for the egr valve and the steel flange on the exhaust side as a cap with the egt probe bung welded to it..could have saved a heap of time if I just did that in the first place.I'm running a 09 model so no hole is necessary. I'm not sure on the temp reading of that spot tho mine seems a tad cool @200deg normal running..sorry for the slight hijack.

 

[Old.Tony]

It seems relevant enough to me, particularly the EGT measured at that point.

It makes me wonder what went wrong with JimmyJay's engine to make things hot enough to melt the butterfly in the EGR valve!

 

[camo.b]

I was thinking that too..if your egr valve is blocked on the cool side of the tubing....so no gas is passing thru.... how does it even heat up that side? I would assune that there wounldnt be any flow that side.just stale exhaust gas.....does much heat transfer thru a 30mm pipe that is 800 odd mm long with no flow?

 

[Old.Tony]

No, not a chance - not normally. That's why there are so many people out there with EGR systems blocked on the intake side with no issues whatsoever.

The thing that is concerning me is:

1) We KNOW that soot builds up in the tube, slowly, over time

2) We KNOW that diesel is injected during the exhaust stroke so that fresh diesel is available for the CAT as a reductant (it needs a hydrocarbon - our cars use diesel, buses/trucks/Mazda CX* use AdBlue).

The combination of these WITH a newly introduced flow (specifically, the failure of the blanking plate) could have caused the fuel-soaked soot to ignite, and with pressure behind from the exhaust flow, pushed this new combustion like a jet through the remains of the plate destroying the EGR valve. This is what I'm assuming has happened given the description.

It relies on the failure of the blanking plate, but I'm still concerned, because even without that failing, the tube before it could fill with soot and fuel and eventually if that ignites it could cause a catastrophic failure, igniting something like a solid fuel rocket motor.

Blanking the exhaust side would seem to be the only real means of preventing it, because then nothing can enter the pipe. For those with late 2010 or later (with EGR flow sensors) this plate would have to have the hole drilled - or look at an alternative, like never paying attention to the EGR valve.

 

[camo.b]

I wonder if jimmy jays egr blank was pre drilled before fitting? With the late model ones is the egr senson looking for heat or gas flow/pressure?would a hole with a air supply satisfy the sensor?...only appilcable if the blank was on the hot side.

 

[jimmy_jay89]

all i know was that i asked for it to be put in

and clearly it was but was not done properly

 

[Old.Tony]

Given that his is a 2007 I would think not - they changed the shape of the EGR gasket.

And with the reported thickness of the "plate" he had in his car, it sounds like someone cut it from foil specifically for the task. Nobody (surely!) would manufacture a plate that thin for sale or supply?

 

[jimmy_jay89]

Given that his is a 2007 I would think not - they changed the shape of the EGR gasket.

And with the reported thickness of the "plate" he had in his car, it sounds like someone cut it from foil specifically for the task. Nobody (surely!) would manufacture a plate that thin for sale or supply?

thats wat im thinking

 

[camo.b]

How many kms have you done with that blank fitted

 

[Old.Tony]

He at least came to Qld and back - passed us between the roundabouts on the north and south side of Armidale!