I used a block tester in my overflow today. I realized that I needed to pull down a few inches of coolant to prevent the coolant from contaminating the indicator fluid when putting in the vial.

OK, with a warm engine idling I started to suck in air over the blue indicator fluid. Instructions said to do this for 2 minutes. I went to 3 minutes. After 4 or so minutes my coolant level started to rise due to heat expansion and I had to take the tester out of the overflow.

Question: is 2 minutes enough to indicate hydrocarbon contamination in the coolant?

 

after 3 mins and still blue, should be OK. should have changed by then, if you had exhaust in cooling system.

 

Thanks Rev. My troubles began when I had a new intake manifold installed. Was getting a CEL for cyl 1. Had coolant leaking. Replaced the leaky intake, which had a cracked corner. truck has 147K miles.

After that, I was getting intermittent over heating. Changed the stat that came with the intake. Still getting intermittent over heating.

Changed the degas cap out thinking the original may have pressure issues. Same issue.

Truck was always pulled over immediately after temp gauge rose.

After sitting, truck would operate within operating range.

Brought back to the mechanic. He said I now have a blown HG. Hmmmm. Blown HG causing the overheat all of a sudden after the intake was replaced? Truck had never overheated.

Decided to give the system a good burp. Found out it needed it. Drove a few days, no problems.

Borrowed a Block Tester from Auto-Zone and purchased the blue test fluid. Cannot get a positive reading for a blown HG. Tried again this morning after drawing out about a half gallon of coolant from the bottle making sure it was at least 1/4 full. Kept the test going for about 5 minutes.

Beginning to think I may have to switch mechanics. Hoping the HG is a non issue now, but will test a few more times.

 

Is it over heating or is the temp sensor bad? If you can't get the blue to change, then HG's are OK. Check clutch fan is working correctly, see if turns very easy or not. ???

 

Not necessarily, it all depends on where it might be blown. It will only detect HC in the coolant if it's blown between the combustion chamber and water jacket. I'd do a compression/cylinder leakdown test.

 

Well, it hasn't overheated since I burped the system, but a compression/cylinder leak down test will be done next.

No oil in coolant and no coolant in oil as far as I can tell. Truck runs great.

 

A Blown head gasket can only cause overheating when its between a water jacket and the cylinder! (combustion chamber)

 

Thanks again Rev. That narrows a few things down.