V6 C25XE Oil Cooler

[GP123]

Hi everyone,

Going to replace my oil cooler in the V6 as i know they are very common to fail in these engines so im putting a new fuel pressure reg and new injectors on the fuel rail anyways so i might as well go on down a bit. A few questions though..

The lower inlet divider is there a gasket etc needing replaced here when removed?

and also what mm size are the 2 nuts on the cover plate holding on the radiator? and are the coolant bridge nuts the same size?

I also have a new thermostat here which i was going to get put on when the timing belt and water pump where being done (not by me lol) i remember reading that access to it is good when installing a new oil cooler? is this true? as if so i will surely unbolt it and fit the new one in place.. its just the hose coming out of it im just wondering if access to it is OK?

Thanks for any help/replies.

[GP123]

also the 2 pipes with banjos at top of the plate i take it these will need to be removed at the front of the engine also to have play in them to get the plate and oil cooler out?

Are they best got at from top of engine bay or underneath and is there anything else needs removed to gain access to them?

Thanks

[Robsey]

Apologies for the lack of answers so far.

There are not many prominant V6 owners on the forum.

I hope that Cavalier342 or James McGrath will have some advice for you.

Sadly, if it has more than eight valves, then I am paddling out of my depth.

[Robsey]

Reading bits from TIS for the C25XE...

Sealing the heat exchanger cover -
Use light grey silicon sealant - part number 9 163 307 (probably should be 90 163 307).

The Haynes manual for the Omega V6 says...

Ensure the mating surfaces of the oil cooler, cover and cylinder block are clean and dry.

Fit new sealing rings to the oil cooler unions
then refit the cover and screw on the large nuts,
tightening them by hand only at this stage.

Apply a bead of suitable sealant
(Vauxhall recommend the use of sealant detailed above available from your Vauxhall dealer),
approximately 2 mm in diameter, to the groove on the oil cooler cover.

Refit the cooler assembly to the cylinder block
and refit the cover retaining bolts,
tightening them evenly and progressively to their specified torque.
Once the cover bolts are correctly tightened, tighten the cooler nuts to their specified torque.

Manoeuvre the oil cooler pipes into position and screw their union nuts into the cylinder block by a few turns each.
Position a new sealing washer on each side of the pipe unions then refit the union bolts.
Tighten the union bolts to the specified torque then
tighten the pipe union nuts to the specified torque.

Fit new sealing rings to each side of the coolant outlet then refit it to the cylinder heads,
tightening its retaining bolts to the specified torque.

Reconnect the hoses to the outlet, securing them in position with the retaining clips,
and the temperature sensor wiring connectors.

Refit the inlet manifold
and install the exhaust manifold heat shield and (where necessary) front pipe.

[Robsey]

I suspect with the heads off, you will indeed get better access to the block, and therefore water pump etc.

I think - If in doubt, get a decent full engine gasket set, and replace all seals and gaskets that you disturb along the way.

As they say - do it properly, do it once.

From my understanding...
You need:-
Chapter 1 - Draining the Cooling System
Chapter 2C - Working on the V6 engines.
and
Chapter 4A- Removing and working on the Inlet manifold.

- from the Omega-B (X25XE) Haynes manual.
Do you have all of these?.

[cavalierian64]

Hi,
Bit late to the party as I've been off the forum a while but owned a V6 since 2004.
It is possible to change the cooler with the heads on, just need to wriggle it out of the vee.
Nice little upgrade while you are there is to fit an Omega lower bridge as they are made of plastic rather than ally in the Cav.Will stop a load of heat soak into the plenum.
A couple of things you should do before getting it on the road is change the cam belt and tensioner and also look at the crank damper for deterioration of the rubber.
My first v6 in bought ,the damper had separated and chewed its way thru the cam belt causing that to fail.
Changing the belt is possible in car but can be daunting depending on your skill level,
If the cars been sat for 17 years the belt is well overdue.

My own v6 went through many upgrades, ended up with a 205hp 3 litre Omega, light flywheel and clutch.
Used to rwyb at Santa pod, PB of 14.4 @98mph.

[Robsey]

I have emailed some more V6 C25XE info.

I hope it helps.

[GP123]

Thanks for the info men..

I had a stab at trying this yesterday morning first thing as i was fitting my new injectors to fuel rail and made my way on down but turned out a disaster had got down to taking the coolant bridge off etc and had just the last divider to remove, i had the thermostat right in front of me also.

Undone the torx screws which had factory almost like loctite on them? like blue in colour on the threads.. and that was it game over... could not get it removed at all! tried leverage etc to get it to come off and was just completely "welded" on.




Was so disappointing to get that far i could see the last remaining torx screws underneath too for the oil cooler top plate to which the wee cooler is screwed onto.

I looked all around for more screws incase i missed any. Ive never came across something like it yet that hard to get off on the engine. There was a gasket on top of it unless something was hiding under it???

The coolant bridge was tricky put back on again also due to the shape of it. But got it on eventually. So still have a new oil cooler but just not on the engine lol.

[GP123]

EDIT**

Omg......

Found this picture while browsing eBay.



There was 4 torx screws hiding underneath the gasket. I didnt touch it as i didnt want it falling into a million pieces on me as i didnt have a new one as there was no mention of there being one on the How to i seen.

Right well now i know. Hopefully get this oil cooler in yet.... lol

[Robsey]

I was just about to look at other V6 threads for info...
Amazing how you find answers in the craziest places.

Yes - I see those four bolt holes in the casting in the last picture...

Big sigh of relief.
The saga continues...
Best of luck with it

[GP123]

Thanks for the support Robsey! lol

@ Ian. If i get the thermostat unbolted to try get the new one on what is the housing attached to? is it a rubber hose or a metal pipe/hose?? there doesnt seem to be a big jubilee clip or anything of that nature to hold whatever it is onto it? or im thinking it just slides inside the end of the thermostat housing...but then whats to stop it sliding off?

[cavalierian64]

The ally pipe is pushed into the thermostat housing and sealed with O rings iirc, this then joins to the top hose, the curly hose on the front left of the engine as you are looking at it.
I remember one of mine was fairly well stuck in and needed some persuading to loosen.
At the other end of the pipe,i.e. front of engine there is a torx bolt onto the head, might hold the dipstick tube aswell.
Undo that and wriggle the pipe out.
Replace the o rings and put a load of grease on the two parts to stop the seizing up again.

[Robsey]

According to that Vauxhall College pdf that I sent you.

It says - unscrew side pipe and remove thermostat housing extension tube.

Haynes call it a transfer pipe which is rigid and has two rubber o rings on its exterior.

It looks like it pushes into the bore of the thermostat housing.

Yep - looks like what Ian just described.

[GP123]

Thanks for replies.. will get stuck into it again this weekend hopefully.

@ Ian you see the wee upgrade your on about is this what you mean here:



Is this fully plug and play for the rest of my engine... its just the injector holes look a bit off compared to the standard one on the c25xe?

Thanks

[GP123]

Update:

Well i didnt go for that black x25xe upgrade, just thought id keep it original as knowing my luck something would be different!

Anyways.. out of work early Fridays means cav time. So got stuck in and continued where i had left off with the Thermostat. What a bitch of a job! an utter crap time. But i got there, after wiggling for what felt like years and lightly tapping the extension pipe with a hammer left, right, up, down the most effective way i got it off straight away was when i had un done the torx bolt holding the dip stick and the ext pipe bracket i put a 22mm spanner between the bracket and the hole and wedged it back towards me and voila straight out!

If not you will be wiggling for hours with no progress made at all. I really was going to leave it but having the new Thermostat sitting looking pretty and not knowing the condition of the thermostat on her made me determined to get the job done, so im happy with that. Put the new one in and then greased the extension tube so its easy peasy for the next person....

Next the oil cooler. I cleared all the gunk and whatever fluid it was/is sucked it all out with a hand grenade and pipe. Cleaned all with a cloth and it came up pretty well to be fair. Got the new oil cooler in and plate on top. Biggest job for this was getting the banjos lined up again, as i had "slightly bent" them out of the way.. so getting them back in again perfect took a good hour or so messing about tapping etc but finally got them in and no rung threads!

So now tomorrow just need to work my way back up to the top.. what to flush the entire coolant system out and add some red stuff. Then next month when the water pumps done ive another jar of red stuff to put in also so hopefully it will have got a good red out by the 2nd go.

Ive gearbox oil here too. I think this needs brought out at top with a hand grenade and piping which i have thankfully.

Then next mission is exhaust.

[Robsey]

Good work,
It is all progress, going in the right direction.

Did you get any pictures of your antics?

[GP123]

Sorry Robsey no real photos of what i done just the few above in earlier posts.

Does any of yous know where the diagnostic plug is on the V6 and can you get the codes flashed on the dash by using a piece of wire just?

Im curious if it has anything stored. The EML goes off when car is started and i cant say ive seen it stay on once since ive owned it. Its just a few things ive changed has got me thinking why it didnt come on... the old lambda sensor was original and looked shot so it has a new one now and then the fuel pump turned out to be the wrong one which was meant for a 1.6 litre petrol engine or below and has a bigger one rated at 3 bar pressure which is what it should be etc.

Thanks lads!

[GP123]

[Robsey]

If the engine light is only on when the engine is NOT running, and goes out as soon as the car starts, then all is good.

If a code is stored (historic) then the light should stay on for approx 4 seconds after starting.

The diagnostic plug is in the engine bay in the near-side (UK passenger side) rear corner, just in front of the scuttle panel.

Here is mine on a C20NE model.. hence the yellow octane plug next to it.



Here is a really old How 2 for the diagnostics "paper clip" test.

viewtopic.php?f=70&t=630

[GP123]

Hi,
Bit late to the party as I've been off the forum a while but owned a V6 since 2004.
It is possible to change the cooler with the heads on, just need to wriggle it out of the vee.
Nice little upgrade while you are there is to fit an Omega lower bridge as they are made of plastic rather than ally in the Cav.Will stop a load of heat soak into the plenum.
A couple of things you should do before getting it on the road is change the cam belt and tensioner and also look at the crank damper for deterioration of the rubber.
My first v6 in bought ,the damper had separated and chewed its way thru the cam belt causing that to fail.
Changing the belt is possible in car but can be daunting depending on your skill level,
If the cars been sat for 17 years the belt is well overdue.

My own v6 went through many upgrades, ended up with a 205hp 3 litre Omega, light flywheel and clutch.
Used to rwyb at Santa pod, PB of 14.4 @98mph.

Now that i have plenty of time on my hands these days with being off work due to the virus, i was reading through this thread again and thought i would ask you about the Omega 3 litre engine Ian. Is this a more tunable engine compared to the c25xe? with it being newer is the ecu easier tuned or does the c25xe electrical side of things run it also?

From what i remember the Omega also had the 3.2 litre engine. Are these just straight swaps in a v6 cavalier?

Thanks.

[GP123]

If the engine light is only on when the engine is NOT running, and goes out as soon as the car starts, then all is good.

If a code is stored (historic) then the light should stay on for approx 4 seconds after starting.

The diagnostic plug is in the engine bay in the near-side (UK passenger side) rear corner, just in front of the scuttle panel.

Here is mine on a C20NE model.. hence the yellow octane plug next to it.

[ Image ]

Here is a really old How 2 for the diagnostics "paper clip" test.

viewtopic.php?f=70&t=630

Thanks Robsey! When i start the car the light would stay there for a second or 2 but then goes out. I think this is because i tried running the car with the MAF unplugged to see if the EML was properly working which it did. Since i got the car last year ive never had the EML come on yet... touch wood.
So thats a good sign that the EML works as should anyway. But do no harm doing it to see if theres anything stored on it from a previous time..Might be interesting.

Well the cav is up at my mates garage it was taken up last week and its sat since due to this virus. All MOT centres are shut here in NI, with some even being turned into testing centres instead for Covid-19.

So i have no idea when the timing belt, water pump, aux belt and aux tensioner will be installed.

Also cat back stainless exhaust to go on, discs and pads all round, calipers painted, full coolant flush with 5 year red being ran this time, sunroof deflector and gearbox oil all to be completed before even thinking of heading for an MOT.

[Robsey]

After 25 trouble free starts, the engine light will go off as soon as the car starts.

Or if you pull the battery for 30 seconds.

As for cat back exhaust... would you not wish to fit that after the MOT?

[GP123]

After 25 trouble free starts, the engine light will go off as soon as the car starts.

Or if you pull the battery for 30 seconds.

As for cat back exhaust... would you not wish to fit that after the MOT?

Thanks Robsey. The exhaust system just didnt survive at all especially the backbox its really badly rusted and awful looking.. the only rust underneath her.

So at Christmas i purchased a Piper stainless steel exhaust system. This bolts onto the cat and then runs to the back. So downpipes seem OK, I think these were stainless from factory? (if somebody knows about that) they seem to have done good.

So in terms of MOT, its completely fine and will pass no problem. As theres still a Cat in place and also a middle box and a rear backbox.. However Pipers worked their magic of course for both sound, performance and looks. Im hoping it serves the cav a longgg time.

[Robsey]

Ah - I see...
My head read it as a de-cat exhaust.
I don't know why.
Maybe I am just a daft old fool.

All sounds like a good plan.

[cavalier1990]

Apologies for the lack of answers so far.

There are not many prominant V6 owners on the forum.

I hope that Cavalier342 or James McGrath will have some advice for you.

Sadly, if it has more than eight valves, then I am paddling out of my depth.

Agree with you there Robsey very little on the v6 on this forum, the omegaownersforum, should have lots of discussion on the 2.5 v6, i use this for my 2.6 omega. Still a good idea to keep a discussion open here as it will build all our knowledge of that model engine, just in case anyone ever buys one down the line (cough) me! I think James had some stuff he done more recently.