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[terry paget]

More pics of the EGR valve. Here is the head, inlet side, showing part of the exhaust gasket

Here is the exhaust side

[terry paget]

I note that 4 studs remain in the head, exhaust side, so 9 studs came out. That's fine by me, as long as no studs break off in the head.
I presume the exhaust gas recirculation is from ehaust side to inlet side via holes cast in the head when the EGR valve opens. That means that all exhaust ports need to be connected.

[dave the builder]

I presume the exhaust gas recirculation is from ehaust side to inlet side via holes cast in the head when the EGR valve opens. That means that all exhaust ports need to be connected.

nope ,
Look at your 2nd picture
exhaust port 4 (far right )lets gasses via the extended Chanel(in gasket,manifold or head) back into the head via the square-ish small hole that is between the 2 studs remaining  far right .

gasses then exit the head casting into the EGR cooler casting (as shown in my previous pics )

if the egr valve is open (only opens above certain revs/speed and varies how much it opens again relating to revs /speed)
gasses pass through the EGR valve ,back to the head casting (via egr cooler) and exit from the small square-ish hole inlet gasket side (see your first pic ,hole far left in gasket ,inlet cylinder 4 )

the gasses are sucked into the inlet manifold for re-burning

thus , EGR

exhaust gas re-circulation 

you can buy EGR blank plates that sit under the EGR valve to block gasses being recirculated
but if you have a "gud un" (one that works ,does not throw up codes for egr faults .or stalls,hesitates etc )
keep it un-blanked , sometimes blanked EGRs stick due to heat build up,crud etc ,report back to the ECU ,EML on ,headache 

EGR valve sucking un-metered air (due to exhaust manifold gasket leak,EGR gasket leak,or the inlet gasket on your engine,a pipe on other engines) can cause major power loss,stalling,poor running,emission problems etc etc

hope the manifold is with you soon so you can get that test sorted ,car back on the road 
 

[terry paget]

Thanks Dave. That achieves recirculation on cylinder 4 when the ECU thinks desirable, but not 1, 2 and 3. Is it a token clean air effort?

[dave the builder]

Thanks Dave. That achieves recirculation on cylinder 4 when the ECU thinks desirable, but not 1, 2 and 3. Is it a token clean air effort?

It only uses/recirculates exhaust gas from cylinder 4 BUT as the gas goes back into the inlet manifold , it mixes with fresh ,metered air and can be sucked by 1,2,3 and 4 cylinders for tr-burn   

[Nick W]

Thanks Dave. That achieves recirculation on cylinder 4 when the ECU thinks desirable, but not 1, 2 and 3. Is it a token clean air effort?

Recirculating exhaust gas is supposed to reduce combustion temperatures. So it doesn't need to be drawn from the whole exhaust system.


So it's definitely a token effort. I suspect that it's effectiveness is within a very small window that matches a specific emissions test. Blanking it off makes no discernible difference to a V6.

[Kevin Wood]

Yep, it's adding exhaust gas to the intake that matters, not taking it from the exhaust, so it doesn't matter if it comes from all 4 pots or just one. In fact, the exhaust manifold is hardly more than a plenum anyway, so it probably mixes all over the place in there anyway.

I'm guessing the intake side is more careful to distribute the gases evenly among the cylinders but I can't remember exactly what it looks like on a 4 pot.

EGR done well is quite beneficial to a petrol engine because not only does it cool combustion of the rather sparse cylinder charge under light load, reducing NOX emissions, but it also reduces the pumping losses against a partially closed throttle giving better fuel consumption.

It's worth maintaining in working order if you can.

[dave the builder]

So it's definitely a token effort. I suspect that it's effectiveness is within a very small window that matches a specific emissions test. Blanking it off makes no discernible difference to a V6.

But this is a 4 banger , unless Mr Paget builds an extension and adds another 2 cylinders 

[terry paget]

Here is the exhaust manifold, 6 missing studs replaced. I imagine the middle row of holes was for the secondary air injection system. The top 3 threads also seem redundant. The RH channel tothe EGR is clear here.

Inlet side. I note the rectangular connection to the EGR. I assume the coolant pipe to the EGR base is the only coolant feed to the head.

EGR base. The 2 electrical connections are for the temperature sensors.

Thanks to all for advice and enlightenment.

[dave the builder]

I assume the coolant pipe to the EGR base is the only coolant feed to the head

no, if you look at a head gasket , there are many coolant channels around the fire rings (as well as bolt holes and 710 ways )

710 is OIL for people who put their filler cap on upside down 

[Doctor Gollum]

EGR channel is built into the coolant bridge... Neat bit of packaging as it probably helps the engine warm up times

[terry paget]

I assume the coolant pipe to the EGR base is the only coolant feed to the head

no, if you look at a head gasket , there are many coolant channels around the fire rings (as well as bolt holes and 710 ways )

710 is OIL for people who put their filler cap on upside down 

I was aware that coolant circulated between head and block. I was changing the head gasket because of a coolant leak. I imagined that cool water entered the head by the EGR base pipe and left it, somewhat hotter, by the pipe at the front of the head.

[dave the builder]

Yep , on some vauxhall family 0 engines, (I've never worked on the one you have) there is a pipe direct from the water pump to the EGR cooler ,then coolant goes through the head back to the water pump
other outlets on the water pump take coolant to the heater matrix and rad ,and overflow to expansion vessel

[terry paget]

For some reason I removed the EGR from the head. Here is its back. Both the gaskets in the gasket kit were wrong, so I bought one from Vx. I imagine the machined groove around the gas channel is for cooling purpose, and the two stumps in the centre are the temperature sensors.

[dave the builder]

For some reason I removed the EGR from the head. Here is its back. Both the gaskets in the gasket kit were wrong, so I bought one from Vx. I imagine the machined groove around the gas channel is for cooling purpose, and the two stumps in the centre are the temperature sensors.

machined slot between gas channel / temp sensor pocket is there so that if the gasket fails , coolant leaks out, down the engine and not sucked into inlet (causing hydrolock ) BANG !
yes to the brass stumps being the ECU CTS (coolant tempreture sensor) ,and the other being the dash cluster sender 
(hence why sometimes the ecu temp reading via scan live data is different to the temp the dash reports )

nice photos BTW Mr Paget