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Cooling system problems

I suspect that there may be air in the cooling system of my car (renault 19) Either that or the head gasket is blown.

I tried bleeding the system by opening the bleed screws (one on the top rad hose, the other on the rad itself) but no air came out, only coolant.

The car runs slightly too hot. Fan comes on a lot, temp gauge hovers just above halfway etc. However it doesn't overheat. The cooling system has recently been drained, flushed and refilled. It was running hot before this and the flushing made no difference. The rad doesn't appear to be blocked and the thermostat was replaced only a year ago.

I notice that if the expansion tank cap is opened when hot, the coolant level rises a couple of inches in the tank and this is accompanied by a release of gas. BTW this isn't a new occurance, it was doing this before the recent flush. I have been told that the level shouldn't rise like this and the rise is indicative of either an airlock or a blown HG. By opening the cap like this does it actually help to bleed the system?

There are no other obvious problems with the cooling system. No boiling of coolant, no leaks, no loss of coolant, no signs of coolant and oil mixing, heater works fine etc. Anyone have any ideas?

thanks brian doyle

Reply to
brian doyle
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Most likely cause is an air lock from when you did your flush. There is usually a bolt that needs to be removed near the top of the head when filling the new coolant. In your case it may be the bleed on the top of the upper hose. Standard procedure is to fill the coolant till it comes out the bleed hole then replace the bolt and top up.

For piece of mind you can check your oil for contamination and see if there is any steam in the exhaust, but it is unlikely. Sometimes you have to drive around for a bit and top up after the motor is warm since the thermostat prevents proper circulation when cold.

Reply to
Shade tree willy

- Is the car losing water?

- With the engine running and warm do you see air bubbles entering the expansion tank? My guess us that you'll answer 'no' to both of those. Doesn't sound like head gasket.

When you release the cap on a hot engine, the water rises because it expands as it gets hot, taking up more space, and the escaping gas is just air displaced by the expanding water.

Possibles for slightly warm but not overheating engine:

- Air lock - sounds like you've eliminated this, though.

- Timing - I don't know if yor R19's ignition timing is ECU controlled or not, but it can make a surprising difference to running temp if it's out.

- Thermostat - yep, they can go wrong a day after fitting or be faulty from new.

- Rad partially blocked internally - did you run the hose through the rad both forward and backward?

- Rad blocked externally (mud, leaves etc.) - youd've noticed this when you removed the stones etc.

- Cheap oil in desperate need of changing - Oil helps cool the engine and it's ability degrades over tims.

Reply to
Chewie

Well sounds as though you have eliminated most of the possibilities. Unless the weather has gone suddenly hot I would suspect the thermistat. You could even remove the thermistat temporarily to see if the flow improves. Sudden rise in the level of the coolant tank sounds like the thermistat letting go.

To check the core feel around the radiator to see if there are any spots in the radiator that are cooler then the rest of the radiator.

Reply to
Shade tree willy

This is normal, it's a pressurrised system and the coolant boils when you release the cap..

If you get rock hard hoses hoses and pressure after a few seconds running, then suspect H-gasket...

Reply to
jb

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