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Discussion Starter #1
Hello guys,

I have one question if someone have more information about pressure range in water coolant system.

One of hose from radiator to engine was cracked in my car and I lose water coolant. Now I waiting for new OEM hoses, but there is long delivery from Italy due to the COVID virus. Somehow I fixed and install other similar hose.
All mechanics said to me that if hose is cracked there is problem with big pressure in system due to the damaged head gasket. I'm a little worried about this and I was start testing and checking if there is some other problem with engine.

I have Alfa romeo 159 SW 2009 with 1750 tbi engine. ECU was remapped by Squadra tuning NL. Engine now produce 400 Nm torque and 230 PS. Test case was to check pressure in water coolant system.Water coolant pressure is in normal drive in 0.4 to 0.8 bar range and coolant temperature is in range between 80.8°C to 91.6°C. Water coolant pressure is in fast car driving on high RPM up to 1.2 bar and coolant temperature rise up to 100°C.

I get this measurement from OBD:

936844


and here is measured pressure in normal drive:


and at driving up to the hill on higher RPM:



From this test case, it seems that everything is fine with the engine and especially with the head gasket. If were the head gasket been damaged, motor will probably have in normal operation coolant water temperature around 100°C and in coolant reservoir we will see bubbles. Also I did not find any cooling water in oil or oil in cooling water, or snowy cream on oil cap. Also belt, water pump and complete service was done 7k km ago.

Turbocharge is cooled also by coolant water an if car is driving fast turbocharger is heated up to limit at 960°C and also water is boiled inside of turbocharger, Complete cooling system id heated up due to this. Is my explanation proper or there is some other explanation?

Best regards
 

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what is the problem exactly? Pressures are fine, car is driving? Replace the cracked hose and you'll be fine? Or am I missing something here...
 

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Discussion Starter #3
Yes car is driving, I was asking about technical information for proper range pressure. From most mechanic I get information that this pressure up to 1.2 bar is to higher for coiling system. I'm not sure about this.

Best regards
 

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I don't know the values for the 1750TBi, maybe check with the mechanic where he has gotten his information.
If the temperature is over 100C the non pressurized area's of the cooling system might see a higher than ambient pressure, this will prevent the coolant from evaporating (along with some of the additives).

Check for other symptoms of headgasket leakage on longer term, such as coolant consumption or milky coolant or foaming oil. The measurement you have done now to me is not enough proof to warrant a headgasket replacement, and if it is failing you might as well be sure before you take the head off. Since it is tuned you wont get any warranty anywhere anyways.
 

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Hello,

I'm sorry, I dont have the answer to your problem, but I have quite the same on my 159 TBi.
A hose broke, coolant leak, I received my New hose from England in 3 days (!), I filled the expansion tank but now I have bubbles in it...
My question is : did you purge the air from the cooling system ? And if yes, where is the screw to evacuate the air ?
Thanks
 

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Discussion Starter #6
Finally I get info. that on TBi engine is normal temperature 88 +- 2°C and 0,98 bar pressure. With engine is all okay, without oil in water or water in oil. If you drive fast on higher RPM, water temperature goes up to 100°C and pressure up to 1.2 bar, because turbocharger is connected to coolant system for cooling and high RPM means that turbocharger is heat up to the limit of 960°C and water is heat up also.

@Arnauuud yes I vent the cooling system. There is one screw on the back side of engine on smaller hose diameter near to alternator. One screw is on the top of the radiator on the driver side near to light. Here on this two screws you can vent the cooling system.

Best regards
 

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Thanks !
I imagine driving without the cooling system vented isn't good for the engine.

And good news for you.
 
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