Head Gasket Testing

[Badglas]

Greetings to all! It's been awhile. I wanted to let you folks know about something I have run into when it comes to using a chemical test to check for exhaust gas in the coolant.

Those of you that remember me know that my grandson and I bought and repaired two PT Cruisers a couple of years ago. Both had been diagnosed with blown head gaskets at reputable shops by way of chemical testing. As I discussed in my build threads on both PT's, neither had a blown head gasket. What both had in common was a plugged radiator.

Over the last two days I have had two PT owners call me with overheating problems. They are similar, so I'll use one as an example.

2003 PT Cruiser that is driven a short distance daily by an older woman. It has been maintained very well and has 75,000 miles on it. The Check Engine light came on so she took it to the local dealer. It had set a code for a faulty thermostat. They replaced the thermostat, upper hose, and a shift solenoid for a total cost of $900. We are still waiting to find out why the trans sensor was replaced. The vehicle overheated the next day. She took it back to the dealer, who diagnosed a bad head gasket using a chemical test.

At this point her son called me. I suggested he have the test verified by someone he trusted before authorizing any repair. Two other reputable shops ran chemical tests and also pronounced the head gasket blown.

Call me a skeptic, but I did not think the head gasket was bad. The symptoms did not fit. When it overheated you could cool it down by turning on the heat full blast. It did not boil over at any time, and the system had been thoroughly purged of air. I suggested that the radiator was plugged. He then told me the dealer had replaced the heater core two years ago because it was plugged. I agreed to take a look.

This is where it becomes informative. I met him at his shop and ran the chemical test myself. It did test positive for exhaust gas. He agreed before pulling the head to replace the radiator. He ordered the $52 one from Rock Auto. He installed it today. He called to tell me that it no longer overheated no matter what he did. I went back to his shop to run the chemical test again just to satisfy my own curiosity. Same kit, same batch of fluid; no exhaust gases detected.

I have no explanation as to why this happened. Why would a plugged radiator cause a false reading in detecting exhaust gas? Maybe Nitro will way in.

What I wanted you folks to be aware of is that I know of four PT's that were diagnosed with bad head gaskets, none of them had blown gasket, all of them had a plugged radiator.

Happy Memorial Day!

Ron

[NitroPT]

There are really to many variables to consider why so many claimed false reading using the Bock Tester. In all the years using it I have never had a false reading. I have used it to test at least a few PT Cruisers for customers as well mine in the last 3 years and never had a problem.

The only way to have confirmed a false reading would have been to follow up using an emissions sniffer at the tali pipe. The ones used for Emission testing which would have been the best way to check for not only for a possible blown head gasket or cracked head but to confirm the Chemical Block tester.

Frankly without trying to point the blame I would have to say it was user error. Unless one of the companies that packages and supplies the Block Tester for years can show any cause other then a contaminated tube or error in application the Block Test method is still the cheapest and quickest way to determine combustion gases in the cooling system.

I would really rather hear from members that take the time to contact a supplier of the Block Tester to report a qualified response rather then those looking on the internet for the answer!!

To conclude my response I would still highly recommending the use of a Block Tester if you suspect a blown head gasket. Read and follow the instruction for its use carefully.



Ron 1 or 2 days is not really a guarantee the problem was solved. Lets see what he tells you in a few day of his normal driving .y

[Badglas]

Originally Posted by NitroPT

There are really to many variables to consider why so many claimed false reading using the Bock Tester. In all the years using it I have never had a false reading. I have used it to test at least a few PT Cruisers for customers as well mine in the last 3 years and never had a problem.

The only way to have confirmed a false reading would have been to follow up using an emissions sniffer at the tali pipe. The ones used for Emission testing which would have been the best way to check for not only for a possible blown head gasket or cracked head but to confirm the Chemical Block tester.

Frankly without trying to point the blame I would have to say it was user error. Unless one of the companies that packages and supplies the Block Tester for years can show any cause other then a contaminated tube or error in application the Block Test method is still the cheapest and quickest way to determine combustion gases in the cooling system.

I would really rather hear from members that take the time to contact a supplier of the Block Tester to report a qualified response rather then those looking on the internet for the answer!!

To conclude my response I would still highly recommending the use of a Block Tester if you suspect a blown head gasket. Read and follow the instruction for its use carefully.



Ron 1 or 2 days is not really a guarantee the problem was solved. Lets see what he tells you in a few day of his normal driving .y

Nitro, I do not disagree with anything you said. That said, it just seemed odd to me. I do not have access to tailpipe sniffer. I hope you would agree that I do know how to use the tester. I had to see for myself because you are correct, most false readings are due to operator error. I'll let you know in a week or two if the PT stays fixed. Assuming it does, do you have any idea what might connect the false reading to a plugged radiator? I can't think of one.

By the way, I am still alive and beginning to think about leaving the cave. Hope all is well with you!

[Busted_PT]

I know that you covered all the bases on the use of the product. You just couldn't sleep if not done perfect, much like our mutual friend Lynn. Very odd. But There are no absolutes in this world. We only let or arrogance and former successes convince us there are.

[ptcruisersteve]

On one of the Block Tester instructions I saw it states that if the test fluid from blue to blue green its okay. If the test fluid changes from blue to yellow you have a combustion leak. The yellow is in bold letters and capitalized. It also says to check the radiator and coolant leaks if the results are negative.

On some posts on this forum I have read that any color change indicates combustion gases in the coolant system so I feel there are some confusion on the test fluid change from blue to blue green. In the beginning stages with only a slight leak of exhaust gasses the concentration of hydrocarbons is low so you would expect only a slight color change.


The question I have is if you get a positive reading on the block test from blue to yellow but you replace the radiator and it doesn't overheat anymore are we just compensating for one of the stages of a blown head gasket?

[NitroPT]

I have an idea about the false reading, but need to try out a test first.
I once had trouble tuning a Motorcycle using my exhaust gas analyzer in the shop where other engines were being run. My samplings were incorrect because of it.

I am also going to consult with U View on Tuesday.

[wb2kki]

That was my thought Just because the radiator fixed the over heating doesn't mean he does not have a blown or leaking head gasket OR small crack.
only time will tell.

He can always send an oil sample to a lab and see the condition of of the engine or do a leak down test.

[Badglas]

Just an update on the PT I referenced in the first post. It has been driven 100+ miles per day without any problems. Just to satisfy myself, I ran yet another test for combustion gases in the coolant yesterday. Nothing detected.

I still agree with Nitro that this test is the most accurate to determine a blown head gasket. I have no clue as to why a plugged radiator would cause a false reading, nor can I find anyone that can explain the false readings.

Ron

[NitroPT]

Ron to much to explain in type. I am calling you right now! You can re-write what we talked about if you choose?

[Badglas]

Greetings all,

As Nitro finds himself buried in work, I'm going to attempt to explain what he found out concerning testing for combustion gas in coolant. If I get something wrong, when Nitro has time he'll correct me.

Nitro, Busted, and I talked by phone after my last post. I will do my best to do justice to the information Nitro uncovered.

All of these testers, regardless of brand label are manufactured by one company. For years they have worked flawlessly. In recent years there has been a small incidence of false positives. The reason for this is due to the chemical makeup of modern anti-freeze, as well as the additives that go along with them, and more importantly, the fact that most people do not flush their cooling systems as they used to.

As I understand from our conversation, as the coolant ages and breaks down it can produce CO2 as a byproduct. This can cause a false positive.

In the case I brought up, the false positive was most likely due to the plugged radiator. The radiator would cause the engine to overheat. As it gets hot, it's possible for the pressure to lift the head and allow exhaust gas into the cooling system. This happens in a fraction of a second. Once the vehicle cools, everything is back to normal. This would also be a false positive.

I believe that there was another example, but I cannot remember for sure. Nitro poured a whole bunch of info into me in a short period of time. Trust me, he researched this with the company that makes the tester and gathered enough info to write a book.

For those of you asking yourself, "What do I do now?", here are a couple of things you can do.

Pretest the antifreeze before running the test. I do not want to get this one wrong so I hope Nitro will explain this when he has time.

The simple answer is if you suspect that the reading is false, drain the coolant and flush the system. Refill the system with water, bleed the air out of the system, and run the test again. If the reading is positive, you have a blown head gasket or cracked head. If it is negative, your coolant was contaminated or there is a restriction causing the overheat which could lead to the head lifting as described above.

Nitro, please correct anything I got wrong. Thanks for getting the answer!

Ron