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[Albus Dumbledore]

Yes I look at the car gauge. But also I feel the hoses, and when all the hoses are scoulding (except bottom rad. hose) I drain the rad and cold water comes out. The warm water doesn't want to enter the rad. The top rad hose gets lukewarm, and the rads cold, no matter how warm the other hoses are. It does sound like the rad core is blocked, but if I put a garden hose through the top hose, water comes out the bottom  :-/ It's so frustrating! And the fan isn't starting at all, since there's no warm water to cool down

[hotel21]

I would suggest a good session with a tech2 and a competent operator reading live data from the car.

Sounds similar to mine in that guage was waaaay too high and hoses seemed very hot and pressurised.  Took TheBoy and M_DTM at a meet to find out that it was the guage that was not properly recognised by the ECU.  Once the correct parameters were set, the needle visibly dropped by 5 or 8 degrees on the guage or more with no other work done.....

Could be the solution to your problems?

[Albus Dumbledore]

Sorry if I sound a bit dim, but I don't understand what you mean? If the gauge isn't recognized by the ECU the water won't flow through? I changed the temp. sensor (actually that's when the problem started. changed temp. sensor and thermostat) a while ago. My temp. gauge on the dash doesn't stop at 100, I just goes up to the red area after a while Pitty I don't know anyone with a tech2

[hotel21]

I am not most clear on this myself, I can only recount what TB and M_DTM accomplished for me.

The guage on the dash relies on one temp sender in the engine and the ECU relies on another, seperate one, as I understand it.  There needs to be some setting made such that both are reading 'similar' values and this requires tech2 intervention.

TB or M_DTM will be able to explain better, sorry......   :-/

[Andy B]

.....
The guage on the dash relies on one temp sender in the engine and the ECU relies on another, seperate one, as I understand it.  There needs to be some setting made such that both are reading 'similar' values and this requires tech2 intervention.

TB or M_DTM will be able to explain better, sorry......   :-/

I think I understood it as it's the dash that's at 'fault' & needs calibrating to the temp sensors.

[hotel21]

.....
The guage on the dash relies on one temp sender in the engine and the ECU relies on another, seperate one, as I understand it.  There needs to be some setting made such that both are reading 'similar' values and this requires tech2 intervention.

TB or M_DTM will be able to explain better, sorry......   :-/

I think I understood it as it's the dash that's at 'fault' & needs calibrating to the temp sensors.

In a nutshell, yes.  The gauge incorrectly reports a high temperature which is in conflict with the info that the ECU is gathering, despite both reading the same water temperature from differring sensors....

[davlad22]

Don't give up!!! Sounds like you've done a load of work to get this far!

Somebody help this guy over the final hurdle! Must only be the radiator that's causing the problems now!?!

[Andy B]

......
In a nutshell, yes.  The gauge incorrectly reports a high temperature which is in conflict with the info that the ECU is gathering, despite both reading the same water temperature from differring sensors....

Another example of being far too complex to achieve a simple end. Cars used to just have a temperature dependant resister that talked to a gauge  .................. that was it!

[philhoward]

If the pressure builds up that quick, then it sounds like either the head gasket or a cracked head.  As for the temperature going through the end stop of the gauge - another stupid question, but the thermostat is the right way round, isn't it?  I can't think of any other way the bottom hose can get hot and the top hose not.

[shyboy]

Please don't give up! When you eventually crack this one there will be many people on here who will share your pleasure at your success.
You've done so much work now that your Omega will be in great shape once this problem is solved. You must be nearly there.
It really does sound like a blocked radiator matrix, even though some water is getting through when you flush it. Have you been able to establish whether the thermostat itself is working properly? The bottom hose would get hot through heat transferring back from the engine block even though it was not passing through the radiator.
As I mentioned in a previous reply, it looks like a replacement radiator might be the answer.
Keep right on to the end of the road.  

[Albus Dumbledore]

Thank you all for the support

Hmm, maybe a new rad is a good idea.
just to clarify: It's not the bottom hose that gets hot, it's all the other hoses. The only one that doesn't get hot is the rad bottom hose. The rad top hose gets lukewarm. Even the ex.tank gets scoulding. It's only the rad left, that's not getting hot.

Yes the thermostat is on the right way. It comes with a housing so it only goes on one way (and I have tried running the car without the thermostat). I tried to test the thermostat (put in water and bring to boiling) and it opens, but I didn't have anything to measure the temp. with to see when it opens.

Maybe I should get a new radiator

[Matchless]

Thank you all for the support

Hmm, maybe a new rad is a good idea.
just to clarify: It's not the bottom hose that gets hot, it's all the other hoses. The only one that doesn't get hot is the rad bottom hose. The rad top hose gets lukewarm. Even the ex.tank gets scoulding. It's only the rad left, that's not getting hot.

Yes the thermostat is on the right way. It comes with a housing so it only goes on one way (and I have tried running the car without the thermostat). I tried to test the thermostat (but in water and bring to boiling) and it opens, but I didn't have anything to measure the temp. with to see when it opens.

Maybe I should get a new radiator

You have had a hard time with this but it is still fixable.

Firstly, it is normal for the coolant system to pressurise as the water heats up and expands, that is why the header tank must only be half full.....the remaining air space is compressed by the expanding water. If the pressure was getting too high then the pressure relief valve built into the header tank cap would release coolant.

Your heater, throttle body and bypass hoses are getting hot so the pump is circulating coolant.
The top hose and radiator do not heat up so there is no coolant flow through them. Therefore, you either have a blocked radiator or a blockage in the radiator circuit or the thermostat is not opening.

The thermostat opens at around 95c, it takes quite a time to get to this temp when idling on a cold day....have you tried driving it?
If you remove the thermostat from the housing and drive the car does the radiator warm up?
Remove top and bottom hoses, check inside for any sign that the inner and outer layers or rubber have separated.....this can cause a blockage without any sign on the outside of the pipes.

[Albus Dumbledore]

I have driven it (with the thermostat in) and it overheats, just faster then if standing still.
Oh, there is another symptom I don't understand. If I have the heater off, and the temp. gauge says 100, if I then turn on the heater the temp. gauge rises to about 105 :-/ Same happens if it's 90, or a 105. If I have the heater on, then turn it off and on again the temp. rises?

Usually (on other cars I have encountered) if the car starts to overheat, you should turn on the heater (on full heat) and the temp gauge goes down (thus cooling som of the water).

I could do this on this car before this problem, but not now. Does this tell anybody anything???

And, is it possible to test a radiator, or maybe dismantle it?

[Mike Collins]

When I had overheating problems with my 2.5, eventually I removed the radiator and took it for flow testing.

It was effectively blocked, flushing on the car was misleading as the water was probably passing through the auxiliary pump instead of the radiator.

Do you have Companies who repair/recore radiators?

Mine was recored and all problems solved.

[Albus Dumbledore]

I do actually know of a company called Radiator service, so I'm guessing they recore.
I'm gonna try taking the rad to a tester.

If I put a garden hose through the top hose of the rad, and water comes out of the bottom hose, can it still be blocked?? Or is it only blocked if no water at all comes out?