thu Posted June 21, 2007 Report Share Posted June 21, 2007 On my 1985 Deville 4.1L, the engine overheated after the waterpump had a catastrophic failure. I took it to a local shop. The guy pressurized the cooling system and the air came out the exhaust. That confirmed that I had a blown headgasket. It was a simple, fast test. I elected to not fix it and junked the car. 238,000 miles, original everything. However, I would surmise that if no air came out the exhaust, that does NOT mean you do NOT have a blown headgasket. You'd have to do the cylinder compression test to be sure. 2003 Seville STS 43k miles with the Bose Sound, Navigation System, HID Headlamps, and MagneRide 1993 DeVille. Looks great inside and out! 298k miles! Link to comment Share on other sites More sharing options...
KHE Posted June 21, 2007 Report Share Posted June 21, 2007 Just re-ran the test. Results after 20 minutes Topped off coolant level. Level had dropped about 2 inches overnight. Air in system? T=0 - 5 min Idled without cap on coolant tank. After 5 min, temp gauge at 12 o'clock. Fans not running T=6 - Closed cap on coolant tank. Started seeing very white exhaust. Temp gauge still at 12 o'clock T=8 - Temp gauge unchanged. Fans not running T=9 - started combustion byproducts leak test. Temp gauge at 12 o'clock T=10 - Fluid had turned green from blue. Instructions only cite blue and yellow as possibilities. T=13 - Fans on. Temp at 1 o'clock. Still getting white exhaust T=16 - Fans still running. Pulled the purge hose (coming into the side of the coolant tank?) It's flowing air. T=18 - Put green test fluid back on, after another minute it turned yellow. . Temperature had backed off a little from 1 o'clock position T=20. Temp gauge still slightly below 1 o'clock. White exhaust. End test. Conclusions? This is why I use the cylinder pressure test. It takes longer but the results are conclusive. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Ranger Posted June 21, 2007 Report Share Posted June 21, 2007 Purge line flowing air might be exhaust gas. If the white exhaust smells like coolant, I don't think you need to test any further. Link to comment Share on other sites More sharing options...
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