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[OhmyOmega]

Hi folks.
Looking for a bit of advice.  This all happened when it was really cold and I fear more than one problem.

Omega 2.5V6 1998~140k.
Has been using a bit of water for a while- nees about a litre a month.  In December I was in down out and cheked the water and there was oil in the expansion tank, list a little on the cap and floating - smelled like warm fresh engine oil.  Topped up the water and drove home~350miles ran a bit hot 97-100+ ut behaved fine.

Just before Christmas drove up to Moray and back in the very cold -15C and no problems.  Since then ...

If I start an run the car temp rises quickly to top, warning light on!  Seems to cool quickly when turned off but quickly rises again if driven.

Running the car without driving see temperature rise to 97-100 but no overheat.  Running the case with the top off the header tank and it goes through a slow cycle of ejecting about 1.5litres then dropping down again - usually with some air.  Radiator did eventually get hot and taking a pipe off the header tank was able to confirm thermostat opening and water pumping. 

From what I have read on here I guess that either there is a head gasket away or a blocked oil cooler.  I am planning to do a compression test at the weekend but have a couple of questions.

The Haynes manual says that there should be no more than 15psi difference between any two clyinders, that's about 5%.  Is it really that critical?

How do I test for a blockage in the oil cooler?

Any other advice or comments would be greatfully received.

Thanks in advance!

John

[Blackie_No1]

I would say it is one of the head gaskets!

[Lazydocker]

Unfortunately the symptoms do sound like a head gasket failed... Could still be oil cooler with sludge stopping the coolant flow properly, but I doubt it

[OhmyOmega]

Thanks guys - rather what I thought.

Any thoughts of the limit of 15psi between any two cylinders?

John

[Marks DTM Calib]

Interesting thoughts by some on here....I personaly am very interested to hear the explanation on how oil gets into the coolant with a failed head gasket.

Discuss.  (note, treat it as a learning exercise  )

[dbug]

Leaking oil cooler mate 

[tunnie]

Interesting thoughts by some on here....I personaly am very interested to hear the explanation on how oil gets into the coolant with a failed head gasket.

Discuss.  (note, treat it as a learning exercise  )

Guessing its not possible, hence you fishing for answers. BUT... it could fail around one of the fire rings? Allowing oil to get into the coolant jacket bit.... BUT not sure how the 2 pressures would react  :-/

The coolant system is under pressure, but so is the cylinder, guessing there is more in there so that would win, pushing some oil into the jacket  :-/

[Marks DTM Calib]

Cylinder pressures are huge, coolant system pressure is just large.

The floor in your thoughts is...where does the oil in the cylinder come from?

[feeutfo]

failed oil cooler in my mind, and thats before seeing Marks post.

Basic rule, and is quoted somewhere on here i believe,
oil in water, oil cooler failed.
water in oil, head gaskit failed.

Take the water tank cap off when hot and it will boil over, the pressureised system prevents boiling.

I wonder if the the boiling and the fact its a 98 has had an influence on replies maybe?

[3.2omegaestate]

Another suggestion into the mix.......and I'm sorry that it is not going to be good news.

What about a cracked block or head between the oilways and coolant channels running inside the block head which has occurred as a result of a blown headgasket causing the excessive temperature you describe and then the temperature causing the block or head to crack 

The explanation of oil in coolant

When the engine starts the oil system reaches pressure almost immediately and will overcome the  reduced pressure of the cooling system at cold. This will allow oil into the coolant as the two systems try to equalise their pressures.

I think whatever the theory, you almost certainly have a serious engine issue headgasket failure, cracked head / block and or failed oil cooler. The symptons you describe regards temperature (not oil in coolant) are exactly what I had a work with an Astra, and the diagnosis was ..........blown headgasket.

Check the compression of each cylinder but also get a sniff test done on the coolant to determine if hydrocarbons (combustion gases) are present in it. If they are then it is a very good indicator that the head gasket has failed. The test is easy to carry out with a dramatic almost instant colour change to indicate failed headgasket. See hear for details http://www.justoffbase.co.uk/Combustion-Leak-Detector-Sealey-VS0061

If you do find it is the head gasket, get the heads skimmed or replacement true (level) heads before refitting to remove any distortion, as you dont want to do this job again in the near future. It goes without saying as well do both head gaskets even if only one has failed, and whilst the engine is stripped down this far consider a cam belt kit and new water pump, to save you time in the long run.

Sorry it is not positive news but good luck.

HTH

[Marks DTM Calib]

Again, still sadly a floored thought.

There is but 1 very small high pressure oil channel in the head, this is some distance from any coolant channels....when heads crack it is more often than not between adjacent combustion bowls and by this stage it would be running like a dog. Thankfuly, craked heads on V6's are unheard of.

It cant come from the oil return channels (of which there are more and they are both large and close to the coolant channels) as these run at a vaccum thanks to the breather system.

Good thought though

[tigers_gonads]

get a sniff test done on your water bottle 

if its just oil then i'd go for the oil cooler

if there is hydrocarbons in there then there is a good chance it's a head gasket 


edit ............ is there any mayo on the dipstick ?

[3.2omegaestate]

Received and understood

Perhaps then as the OP suggests he has more than one problem. Blown oil cooler hence oil in water (well documented) and blown headgasket hence the high temp, etc but at this stage not sufficiently advanced to get the water into the oil (the dipstick test) but would be proven by snif and compression test, or snif test alone but not compression test alone.

Reasoning: poor compresion can be caused by other things as well e.g. piston rings etc, the snif test is for testing h.g. failure, cracked block alone and when used with compression test hopefully will identify which bank and cylinders the breach has occurred at.

Still change both headgaskets though.
One of the most common reasons for h.g. failure is poor maintenance i.e. not replacing antifreeze on a regular basis. Anti freeze has corrosion inhibitors in it that deteriorate after time hence the change interval (2 years ? am I correct please advise) to maintain the corrosion and antifreeze properties.
 
HTH


Must type faster than tigers gonads.......

[Marks DTM Calib]

The answer is ....do nothing and assume nothing....until the diag is complete.

talk of headgaskets and even oil cooler at this stage is premature...

[Marks DTM Calib]

get a sniff test done on your water bottle 

if its just oil then i'd go for the oil cooler

if there is hydrocarbons in there then there is a good chance it's a head gasket 


edit ............ is there any mayo on the dipstick ?

Sady, not nearly as conculsive as it used to be...this test can give some very eronius results