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[Mike Collins]

As I found, the core was blocked, flushing appeared to be bypassing the core, probably through the auxiliary pump.

[shyboy]

It really does sound like a blocked radiator core. I'm not completely certain about this, but if your heater is off, static water will still be heating up to differing high levels in parts of the system, (eg. the engine block perhaps), and as it is not being cooled through the radiator this could show a temporary increase on the temp. guage when you open the heater matrix until that hotter water mixes with the rest of the system and equalises in temp., albeit too high.
I'm not sure that's a good description of what I mean, but I hope you understand.
Don't you dare give up on this yet.  

[markey mark]

i would defeinatly go for a new rad bud classic signs cold bottom hose !!

[Albus Dumbledore]

I think I know what you mean, and no I haven't given up I thought I should have my radiator testet, to se if it's working properly.

I does sound like my problem is the rad, but what confuses me is that when I disconnect the rad from the rest of the system, and put a garden hose through the top rad hose, water comes out of the bottom hose. Can it still be blocked then?
Or maybe sufficiently block for my problem?

[markey mark]

I think I know what you mean, and no I haven't given up I thought I should have my radiator testet, to se if it's working properly.

I does sound like my problem is the rad, but what confuses me is that when I disconnect the rad from the rest of the system, and put a garden hose through the top rad hose, water comes out of the bottom hose. Can it still be blocked then?
Or maybe sufficiently block for my problem?

yes mate it will find a way round with higher pressure but when connected to engine pressure is lower and struggles to get round hence why it gets too hot !!

[Albus Dumbledore]

New radiator, no change. Same problem

[TheBoy]

sorry, just read this.

I'm wondering about blockage along coolant transfer pipe or coolant bridge (or hbv), preventing circulation.

Additionally, the rad switches for fans are near top hose so they should come on when hot, though frequently fail after oil cooler...

[Big_Roger]

Hi,
I am only familiar with the 3.2 V6 engine, but have been following this very intriguing problem. More twists than watching Eastenders!!

I just wonder that at the very start when you did the engine change etc, have you used the correct head gasket, and is it the correct way up? maybe there is no passage from cyl block to cyl head? (as I say, don't know about your engine, but on 3.2 hot water exits engine from the cyl block)

You have done so much work and seeming tried just about everything it's surely got to be something so simple wer'e all missing it !!

Keep up the good work.

Roger

[Kevin Wood]

Another stab in the dark (which may not even be relevant to this engine). You say the engine came from a Vectra. Is the water pump driven by the cam belt or the aux. belt on this engine?

I have seen engines where the aux belt run is different on different models, so the water pump turns the opposite way. This requires a different water pump since the impellers are angled incorrectly.

I'm wondering if the engine, as fitted to the Omega, therefore requires a different water pump and the pump you have is running backwards and thus not effective.

I said it was a stab in the dark, but you seem to have covered all obvious issues.

Has the head been off this engine, or was it a replacement after you changed the HG on the old engine?

Kevin

[Kevin Wood]

Couple of other things to try:

Run it with the thermostat completely removed. Do you get circulation of warm water through the radiator hoses? Does it go the right way (top hose warm, bottom hose cooler)?

Bypass the heater circuit completely with a length of hose (taking out the HBV and everything else, so you just come out of the engine and back in). Does the system now flow coolant through this hose?

Kevin

[Albus Dumbledore]

The new engine (from a Vectra) is identical to the old Omega engine I  had. Only had to change sump, block brackets and inlet manifold. The new engine was complete with cylinder head fitted (I asked so I wouldn't need new head gasket and cyl. bolts:) ). The water exits from the cyllinder head through a coolant bridge (think it's called that), and on the coolant bridge the thermostat is fitted. Then now in easter times I decided to change Headgasket (just so I could rule that out), in addition I fitted my old cylinder head (since I new it worked properly). The HG is the right way ut It's printed on the gasket witch way's up:) (and I tripple checked too ), and I cleaned the block water channels and the new cylinder head since I was down there.

The waterpump is driven by the timing belt (cambelt), and I compared the waterpump already fitted to the new engine with the pump from the old Omega engine.

I haven't tried bypassing the heater circuit, so I'll try that, and see want happens. I'll try just about anything, cause I don't know what else to try:)

witch is the coolant transfer pipe? and with the coolant bridge, if I disconnect the retur hose (one that goes from CB to inlet man. and then continues to eks. tank) hot water comes out. It's fitted right before the thermostat.

[Kevin Wood]

OK. As I said, a stab in the dark.

There should also be bypass flow through the thermostat housing. Sometimes this is provided by the heater circuit, sometimes there is a separate hose or two, perhaps routed from the thermostat housing through the throttle body down to the bottom hose connection (pump inlet). (wish I knew this engine better)

If the bypass flow is not there due to a blockage, etc. and the thermostat is on an external housing, which it sounds like it is, it could be that the thermostat doesn't respond to true engine temperature becase it is sitting in a "dead end" of cold coolant. It's vital that the base of the thermostat has coolant circulating around it when the 'stat is closed, son that it responds quickly to coolant temperature.

I'm not sure how this happens on this engine but perhaps a faulty HBV or something is preventing this bypass flow - hence the suggestion to bypass the heater circuit. Running it without the stat temporarily will also eliminate this as a sanity check that the coolant is being pumped around OK.

Kevin

[shyboy]

Don't let's forget that the start of this problem was oil contamination of the cooling system. I haven't experienced this (yet  :-?), but know that clearing the narrower parts of the system can be very very difficult. Have you found and used the specialist degreaser to which I referred in an earlier post?
Was the replacement radiator brand new or had it seen previous service?
BTW, the coolant transfer pipe is the metal tube connecting the thermostatat housing to the top radiator hose, (it runs through a tunnel in the block), and the coolant bridge is at the back of the V connecting the two cylinder heads.
Kevin Wood's 'by-pass' suggestion should provide some more clues.
I know we all seem to be clutching at straws now, but have you actually removed all the hoses, (even large bore ones), to be certain that they are quite free of obstructions.
The only other thing I can suggest is to bring the car over to the Lake District meet and let everyone have a go at it.  
Sorry to be frivolous.    I do hope you get this sorted out soon. it must be driving you mad.

[shyboy]

I've just remembered that this is a 2.0l engine, so i don't think my comments about the coolant transfer pipe etc. applies. Sorry!.

[Albus Dumbledore]

Well, my fantastically long thread is back I had the car at one garage, waited 2 weeks so they could look at it, when they finally did, the recommended another garage that had more experience with Opel, so then I waited another 2 weeks for THEM to look at it. They changed the rad thermo- switches, and said that now there is some circ. but not enough. That the fan didn't cut in till about 100 Celsius. I took the car out of there (right after they ripped my arm of for payment),  and found out: still no circulation, and the fan DIDN'T cut in.

Now I have resumed degreasing and flushing, and it seems that there's still (after already 10 ltr of degreaser) alot of gunk in the system.

And then I noticed today, when the car was running, I tried turning on the A/C and suddenly the rad fan came on with the A/C fan, and the car cooled down!! When I turned of the A/C the rad fan stopped too, and when I turned it on again the rad fan came on again!??! It cooled the car down to 70 Celsius (then I turned the A/C off).

When I turn on the A/C (push the A/C button in the car) are both fans supposed to start?? I thought it was only the A/C fan behind the front/grill that was supposed to start, to cope with the extra heat?? Or have garage no. 2 done a wrong turn with the wiring??

At least I am happy now 8-)