Omega Owners Forum
Omega Help Area => Omega General Help => Topic started by: Murph on 30 December 2012, 20:58:11
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I've had a persistent coolant leak on my 2.5 since I've had the car (about a year now!). In the spring I changed the HBV for a pattern part (I know!) which made no difference, so last weekend I got some new dowty washers and hollow bolts and got spannering.
I found that the old washers were pretty buggered and the bolts quite crusty, so I was confident that I would now have no more problems and topped up with antifreeze.
It's now worse!
I now have no heating at all and the coolant needs topping up every few days. The car will overheat if sat in traffic even if the expansion bottle has plenty in it. 5 mins from home steam can be seen coming from the passenger side of the bonnet.
Today I got it warmed up and started investigating again and found water dripping down from the back of the engine, passenger side.
The water is mostly dripping from the engine/gearbox join and the crank sensor is wet.
So.... can anyone suggest anything up that way that I should be looking at?
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That is where my 2.5 leaked when the head gasket started weeping (sorry :()
I drove it for months before finally doing a pressure test on the cooling system that confirmed it.
The rear of the passenger side (2,4,6) bank seems to be the only place where V6 head gaskets ever fail (and that doesn't happen often).
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Think mine may have a similar very minor leak as often can smell burnt coolant and level drops by around 3 cms over a 4-6 week period.
Every seal/washer and pipe has been replaced along with thermostat/coolant bridge/HBV/etc etc but still can,t cure it.
I have now come to the conclusion that at 14 years old and 215k under her belt she is entitled to being a little in-continent ;D so just keep an eye on the levels and top up as required :y
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As you have changed the washers & bolts on the coolant bridge and the leak is now worse than before .
I would try & get a mirror on a stick down the back of the engine to see that after all the pulling about etc. changing washers/bolts It is not a hose that is weeping /split worse than it was before .
There are a few rubber hoses round the back there. HBV /Heater etc.
Sorry cant be more helpful but would double check those first before you start worrying about a head gasket .
Pattern HBV is a worry though :-\
HTH ;)
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Oil cooler plate or thermostat?
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Did you notice a telltale stain or trail of coolant whne you had the manifold etc. off to do the dowty washers ?
If there was one it should have lead to the cooler plate or stat area ime,if not as Al said,check hoses etc. around the rear of the engine,and fit a genuine HBV while your in there imo.
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Do a pressure test on the cooling system. Any thing else is just guess-work.
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Thanks for the advice so far fella's.
I forgot to mention... I pressure tested the coolant system today and it holds 2.3 bar with no drop over 10 mins.
With the engine running at fast idle the pressure rose to just over 2.5 bar (into the red on the gauge) and held there fine.
Still no heating after that!
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a blocked heater matrix can cause the coolant flow to change and thus affect the cooling of the engine. Hence the overheating. Leak could be anywhere but I'd just check the unions of the pipes through the bulkhead.
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I think it has been proved that most head gasket failures where on 98 3.0 engines, 2.5 seem to be ok but hbv would be the first check then oil cooler plate and then the seal at the back of the engine block where the coolant transfer pipe joins the block.
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Istr hearing of the occassional rusty core plug at the back of a head leaking. :-\
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Thanks for the advice so far fella's.
I forgot to mention... I pressure tested the coolant system today and it holds 2.3 bar with no drop over 10 mins.
With the engine running at fast idle the pressure rose to just over 2.5 bar (into the red on the gauge) and held there fine.
Still no heating after that!
Did you try the pressure test with both heating on & heating off ?
As your leak has got worse since you changed the dowty washers & bolts . . i would be looking at something you have moved or pulled as you done that job :-\ :-\
Get the scuttle off so you can have a better look down that rear engine area with it running.
Probably do no harm to flush out the heater matrix as well
HTH
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I think it has been proved that most head gasket failures where on 98 3.0 engines, 2.5 seem to be ok but hbv would be the first check then oil cooler plate and then the seal at the back of the engine block where the coolant transfer pipe joins the block.
Mine was a 1994 2.5
I suspect that coolant maintenance (or lack of) is more significant than the year of manufacture.
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Thanks for the advice so far fella's.
I forgot to mention... I pressure tested the coolant system today and it holds 2.3 bar with no drop over 10 mins.
With the engine running at fast idle the pressure rose to just over 2.5 bar (into the red on the gauge) and held there fine.
Still no heating after that!
You are not looking for a big leak. I doubt whether you will see a drop in pressure.
What I did was take the inlet manifold and trumpets off, plug the pipes to the throttle body, and then left it pressurised to about 1 bar /14.7 psi.
I left it for a couple of hours and then went looking for leaks.
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Lots to think about, thanks.
I'll get in there and have a good look at the weekend now that I have a few ideas what to look for.
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I managed to get an hour spare to have another look today, so off came the scuttle.
I had a good feel around behind the engine but couldnt find anything definite. I followed the coolant transfer pipe around the back (that's the stainless pipe that goes along the drivers side and round, right?) and that was dry all the way round and underneath where it joins the engine.
The HBV was not leaking and seems to be working, but I refitted the GM one anyway. While the pipes were off I blew into the top matrix pipe and got an easy flow from the bottom one, so the matrix seems clear.
The only place that felt wet was below the coil pack mounting plate, but I couldnt see in there so I'm still in the dark.
So... thats as far as I got before I ran out of light, but maybe one of you more knowledgeable types might have it narrowed down?
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I managed to get an hour spare to have another look today, so off came the scuttle.
I had a good feel around behind the engine but couldnt find anything definite. I followed the coolant transfer pipe around the back (that's the stainless pipe that goes along the drivers side and round, right?) and that was dry all the way round and underneath where it joins the engine.
The HBV was not leaking and seems to be working, but I refitted the GM one anyway. While the pipes were off I blew into the top matrix pipe and got an easy flow from the bottom one, so the matrix seems clear.
The only place that felt wet was below the coil pack mounting plate, but I couldnt see in there so I'm still in the dark.
So... thats as far as I got before I ran out of light, but maybe one of you more knowledgeable types might have it narrowed down?
Hmm.
That was exactly where my head gasket leaked :(
The other possibility is that one of the core plugs in the back of the cylinder head (that hide under the coil mounting bracket) is weeping.
Check first that it isn't water from the scuttle .....
Core plug can be changed (with difficulty) with head in position. Your next task is to take the coil mounting bracket off and test again to see if it is the gasket or the core plug.
(http://homepages.nildram.co.uk/~aholter/DSCF0741.jpg)
I couldn't face doing the headgaskets in the car (and I already had a hoist and engine stand) so I lifted the engine out to get a better look.....
In the second photo I have reconnected the header tank and have pressurised the cooling system. Water is weeping from the rear of the headgasket.
(http://homepages.nildram.co.uk/~aholter/DSCF0789.jpg)
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From the look of that pic (just what I needed btw) it's defo either a core plug or head gasket. :(
I'll have to find a mirror methinks.
Thanks for the clarification Andy.
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Just in case.....
How much is a head gasket set on trade?
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Strange how most of the head gaskets go in the most awkward of places to find ::) What year is your car murph ?
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Just in case.....
How much is a head gasket set on trade?
I used the HG and bolts from Trechii on ebay, exhaust manifold gaskets from GM (use the newer MLS ones), cam cover gaskets GM, obviously.
Reseal oil cooler plate whilst there.
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Will do TB.
Car is a 1998 2.5.
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I had no chance to look at the mega today due to being kept busy with my mates van suspension, then another mate popping the radiator on his Carlton (we only fitted that one yesterday after he popped the last one!)
I did manage to get a loan of one of those flexible scope things to get a look down the back of the engine.
The battery is dead so I'll charge it tonight and have a play tomorrow.
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look closely at the rubber hosing at the back of the engine, around coolant bridge area. Pinholes in this area squirt coolant away from the hoses! On our 98 Elite Estate had a leak at back of engine - eventually found a small split/pinhole on one of the hoses from coolant bridge close to pipe clamp. As your leak seems to have worsened since you replaced coolant bridge seals, more likely due to you disturbing a pipe or not fitting the coolant bridge seals correctly. Unlikely a core plug or head gasket leak will suddenly worsen following the work you have carried out! ;)
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I'll check everything with a self-critical eye! :y