block tester

[sk47]

Hello; I was in a store today and overheard a man asking about a "block tester". I did not know of this tool. It uses a chemical to check for combustion gases in coolant. Does anyone know about or have experience with this? Would seem a way to check for a bad head gasket of cracks in a head or block.

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[ice445]

Yes, I have one. It's just a simple chemical called bromothymol blue. Its blue in its normal state because it's a base. Any sort of acid will lower its pH and cause it to change from blue, to green, to yellow. CO2 passing through it creates carbonic acid. CO2 is the most common pollutant you'll find in the cooling system if you have a bad head gasket or a cracked head. Not the only one it can detect, other combustion byproducts can change it as well.

My only problem with this test is that the failure that will make it test positive is usually easily observed for free if the failure is bad enough. You'll have excess pressure or bubbles in the coolant even when the engine is cold most times. Supposedly these are good at finding small leaks that may need future attention, but its hard to say for certain. If you use this on a car that works perfectly but it turns green, it may indicate a problem, but it may not. The internet is light on info for the intermediate state. I've heard organic acid coolants that are degraded can cause it to change color. As a personal example, my Taurus will turn the test green after it heats up. But the car has already had head gaskets done before. It uses no coolant and doesn't overheat, nor does it generate pressure in the cooling system. It doesn't have any cylinders even slightly down in compression either. So, it's "failing", but for what reason I couldn't tell you.

Tl;Dr, there are better methods. Hydrocarbon sniffer, visual analysis, leak down test, etc

 

[sk47]

Yes, I have one. It's just a simple chemical called bromothymol blue. Its blue in its normal state because it's a base. Any sort of acid will lower its pH and cause it to change from blue, to green, to yellow. CO2 passing through it creates carbonic acid. CO2 is the most common pollutant you'll find in the cooling system if you have a bad head gasket or a cracked head. Not the only one it can detect, other combustion byproducts can change it as well.

My only problem with this test is that the failure that will make it test positive is usually easily observed for free if the failure is bad enough. You'll have excess pressure or bubbles in the coolant even when the engine is cold most times. Supposedly these are good at finding small leaks that may need future attention, but its hard to say for certain. If you use this on a car that works perfectly but it turns green, it may indicate a problem, but it may not. The internet is light on info for the intermediate state. I've heard organic acid coolants that are degraded can cause it to change color. As a personal example, my Taurus will turn the test green after it heats up. But the car has already had head gaskets done before. It uses no coolant and doesn't overheat, nor does it generate pressure in the cooling system. It doesn't have any cylinders even slightly down in compression either. So, it's "failing", but for what reason I couldn't tell you.

Tl;Dr, there are better methods. Hydrocarbon sniffer, visual analysis, leak down test, etc

Hello; I have used bromothymol blue in a lab in the past. Thanks. I have replaced a few head gaskets and used the old school tests.

Got fooled badly once. Friend had a VW golf gasoline engine. When it would not start, we found water in a cylinder after removing a spark plug. We removed the head but the gasket looked good and the head looked good. Finally noticed the water in the cylinder was clear water without antifreeze in it.
Had a look around and found the valley pan under the cowl just in front of the windshield and in the wiper area had water in it. The drain was stopped up with leaves and crud and would fill up with rainwater. There was a hose which ran from the intake to that pan under the cowl. Not sure why VW did that. Anyway a lot of work which could have been avoided.

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