1991 Holden Rodeo unusual air bubbles in overflow

1991 HOLDEN RODEO
300,000 MILES • 2.6L • 4 CYL • 2WD • MANUAL
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KIRKY96
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Hi my Holden rodeo lately has been blowing air bubbles into the overflow. I first noticed it 1 afternoon after driving the car when I shut it off I could noticeably heard it bubble constantly for approx 5 seconds then settled down. After that I hear noises like air coming through the over flow when I am accelerating and more noticeably when going up or down hills. I have spoken to other mechanics and they all had there different opinions; one said that either the head is cracked or the gasket has blown, another 1 said it was the radiator cap wasn't sealing correctly and letting air get it in and another 1 thought that the radiator cap was the wrong 1 for my car and could be cause it to over pressurize. Well I have gotten another radiator cap that is correct according to the part list at the shop I got it from and it is still doing it. Also when I squeeze the return pipe to the radiator I can feel that there is bubbles there. I have checked that the oil hasn't gone milky and the car runs fine otherwise. Any advice would be great.

Thanks.

Nathaniel Kershaw
Jun 20, 2014 at 10:03 PM
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CARADIODOC
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There's a real fast, easy test to check for a leaking cylinder head gasket. It involves drawing air from the radiator through a glass cylinder with two chambers partially-filled with a special dark blue liquid. If combustion gases are present, the liquid will turn bright yellow.
Jun 20, 2014 at 11:48 PM
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KIRKY96
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hi thanks for your help. what is the name of that test is there an official name for it that i can ask a car shop for ??
Jun 21, 2014 at 12:09 AM
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CARADIODOC
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Nope. I call it the "sniffer" test but in reality you're just using the tool. It would be like saying what's the name of the test for using a wrench. Almost every repair shop has one of these and many mechanics have their own. You can borrow it too from auto parts stores that rent or borrow tools, but they will make you buy a bottle of the liquid. That's because it will be rendered ineffective if it freezes or gets antifreeze in it. By making you buy your own fluid, you are insured the liquid won't be contaminated.

If your mechanic has never heard of this tool, I can search for it on one of the tool vendor's web sites. It might be called a "block leakage tester" or "combustion leakage tester"
Jun 21, 2014 at 1:25 AM