# low coolant pressure



## petro2001 (Aug 8, 2013)

low coolant pressure, I have a 2010 Hyndai Elantra 

about a month ago, my coolant light came on and the coolant was low, I replaced it and ran it for a few mins with the cap off to get any air bubbles out, it was fine, 

a month later my light came on again, and the coolant was low again, I had a pressure test done on it, and it started at 18 and about a half hour later it was down to 11, can you tell me what might be wrong?

I checked the oil and it was fine no milky looking 

someone said a head gasket, im hoping not, but what do you think, i put a new radiator cap on it, and there isnt any place inside the engine that appears wet, and its such a slow leak, i cant tell where its coming from on the ground


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## Paquadez (Jun 9, 2003)

Loss of coolant:

If the cooling system is losing coolant then simply put, you have a leak!

Head Gasket problems do not necessarily result in water (coolant) mixing with the oil.

A faulty head gasket can mean water is leaching into the combustion chamber and evaporating thru the exhaust.

Often, this does not occur with a cold engine on initial start: it only manifests when the block/head reach working temperature.

Alternatively, combustion pressure over-pressurises the cooling system: cooling systems run at a nominal pressure between 13 - 30 PSI, depending on vehicle.

Is white vapor emerging from the exhaust? Classic indication of coolant entering the combustion chamber.

Are there are any signs of coolant escaping from the header tank etc? Indication of excessive coolant pressure.

Your next step is probably to have what is called a Cylinder Leakage Test carried out: similar to a Compression Pressure Test, however, the leakage check tests the integrity of each cylinder by pressuring it (cold) to circa 200 PSI when both inlet valve/s and exhaust valve/s are closed, and checks how long the pressure takes to leak away.

By the (skilled) operator listening to the exhaust, inlet manifold (Air filter e.g.), dipstick hole, radiator, the source of any leak can be established, where cylinder pressure drops rapidly.

If you are losing coolant, the it must be going somewhere!

A final check is to check the coolant for hydrocarbons using a chemical reagent liquid.

http://repairpal.com/how-to-test-for-head-gasket-failure


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## gurutech (Apr 23, 2004)

Check under the car after it's been sitting for a while (a day or so), and if you see any green or orange (depending on the type of coolant), then you may have a radiator or water pump leak. I just replaced the water pump on my truck, and it wasn't so bad, other than stripping a bolt and having to drill it out and "jury rig" the thing to work properly.


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