My son's 97-OBW-2.5L-135k mi suddenly started to overheat and blow coolant
into the overflow. We confirmed combustion gas in the coolant using a
"Head-Gasket Leak Test Instrument" (Snap-on stock #YA2000, a must tool for
this work). I expect a low coolant level, cause unknown, allowed air to
enter the jacket resulting in a hot spot which over heated the head.
Decided to try "Bars Block Seal Head Gasket Repair", following the
instructions verbatum with exception that the stat was removed to enhance
circulation. Tested post treatment with water in system - no over heating
or combustion gas being detected. Drained water thru the stat housing
(only 3qts. of the 6.3qt coolant capacity comes out), installed the stat
plus 3qts. anti-freeze. Thought I was home free, but testing resulted in
over heating. The lower radiator (return) hose was cool, with significant
wellowing of coolant out the radiator vent and fill neck!! Still no
combustion gas was detected. Concluded that hot coolant was not reaching
the stat so it remained closed, but why?? Had to be entrained air keeping
hot coolant away from the stat. After 2 beers and alot of head scratching,
it dawned on me that some stats have a small bleed hole in the body.
Repulled the stat to check it. No hole, and this was the original stat!!
With nothing to loose I drilled a 3/16" hole and re installed. Coolant was
slowly added as the system came up to normal temp with a lot of air exiting
the vent plug. The coolant topped out with no bubbles of any kind and the
temp gage stayed in the normal range. A severe road test revieled cooling
problem solved. The test will be how long the BAR'S sealent holds in
place. So the lesson learned is to monitor the coolant level and should it
ever get low or the system flushed, make sure the stat has a bleed hole
before recharging with coolant. By the way, all this work was done with
the front wheels on ramps to exaggerate the radiator neck and vent above
the jacket to enhance any entrained air to seek the system high point to
be expelled.
