About a month ago I asked if anyone had any experience repairing a blown head gasket using a product called Thermagasket. No one had, so I thought it would be interesting to conduct a test on my 6.5L to see if it worked. I promised to post results on the forum. I finally got around to it.

First, background: I think my head gasket was damaged when my serpentine belt came off during a road trip and the temp gauge pegged above the red before I could pull off the Interstate. There were no major symptoms for several months, but eventually the head gasket failed and 1) the coolant system began to be pressurized by the leak, and 2) coolant began to leak into a cylinder. Over the space of a week things deteriorated to the point that I could go only about 10 miles before enough coolant would be blown out of the expansion tank for the engine to begin overheating. In addition, when the engine was off coolant would leak into the cylinder and cause hydrolock.

Hint: If you wait long enough with a hydrolocked cylinder, three weeks in my case, the coolant in the cylinder may leak out and the engine can be started. Drain the coolant, be patient, and you may be rewarded.

The Fix: The Thermagasket kit for diesels costs $199 plus shipping and consists of two parts (called A and B). Using it is simple: basically remove the thermostat, flush all ethylene glycol out of the coolant system, pour the Thermagasket into the radiator, fill with water and run the engine. (There are some minor details I won't get into here). I know - it sounds too good to be true. To start the repair process the truck then needs to be driven for 50 miles at highway speed with the OD off. I was watching the temperature gauge like a hawk during this stage but it reached the 10 mile point with no overheating. Then it passed 12 miles, 15, 20, 30 and 50! Still no coolant loss or overheating.

The next day I repeated the 50 mile drive and still no coolant loss or overheating. I re-installed the thermostat on the third day and did another 50 mile trip. The temperature gauge stayed solidly on 185F even in the 95F central NC heat!

The Results: I know there are going to be some naysayers out there, but I really think the Thermagasket works! I've now driven it 150 hard miles with about ten full-throttle freeway entrances with no problem. The MINIMUM estimate I got to replace the head gasket was +$2,000 (note the plus mark), while the Thermagasket test only cost $199! Except for the Bridgestone Revo tires I bought so the van would actually stop when I used the brakes :), the Thermagasket may be the best money I have spent on this truck.

The Future: With the Thermagasket still in the system I am supposed to drive the truck at least 15 daily highway miles with no OD for the next 10 days, and then drive it ~10 miles everyday for 30 days. No antifreeze can be used so its best to do this in the summer. At that point I am to flush the Thermagasket out of the system, install a new thermostat and add a 25/75 coolant mix. The big unknown at that point will be how permanent the repair is. I'll report again with Part 2 of the test at the end of the 40 day break in period. Part 3 of the test will be a long term (1-year) reliability evaluation.

Sounds like a great temporary fix when in a jam...I'm interested to see just how long this thing lasts for you. The other concern I'd have is where does the excess "Thermogasket" go...sure, some of it fills in the cracks, but certainly not all of it. I'd worry about it filling in some of the water jackets, ultimately impeding flow...increasing heat in those areas. Best of Luck to you on this one...and THANKS FOR SHARING.

Sounds like a great temporary fix when in a jam...I'm interested to see just how long this thing lasts for you. The other concern I'd have is where does the excess "Thermogasket" go...sure, some of it fills in the cracks, but certainly not all of it. I'd worry about it filling in some of the water jackets, ultimately impeding flow...increasing heat in those areas. Best of Luck to you on this one...and THANKS FOR SHARING.

IIRC when I researched it, the excess stuff will come out when the engine is flushed, (just before the fresh coolant is installed) the components only "harden" in the presense of compression, so inless it reacts with the heat/pressure of cylinder pressures, it remains in its unharded state.
if it works like it is susposed to, it can buy an owner time to save money or source a new engine.
I talked to a local rep here who gave me a brief description of how it works, (thermalweld) BUT here it is installed by the rep as they will not sell to the general public. if it cures the problem they send you on your way with a warrentee, if they cant fix your coolant problem they refund your money
...........I'm a mechanic by trade but I think it can be used to buy a fellow some time, for a proper repair, but I'd be interested to see how long it lasts and if it can be trusted

...Keep us updated!

Sounds like a great temporary fix when in a jam...I'm interested to see just how long this thing lasts for you. The other concern I'd have is where does the excess "Thermogasket" go...sure, some of it fills in the cracks, but certainly not all of it. I'd worry about it filling in some of the water jackets, ultimately impeding flow...increasing heat in those areas. Best of Luck to you on this one...and THANKS FOR SHARING.


Thanks for your comments. I am hoping that the excess just gets dumped when I flush the system in 35 days. According to the manufacturer the Thermogasket material does not coat the entire cooling system but bonds only where there is excessive heat (such as a crack or gasket break). If there are no hot spots the material just keeps circulating in the cooling system.

I was doubtful of the product when I started and frankly had very low expectations, but so far everything they have claimed has been accurate. My confidence in the manufacturer is increasing fast and they claim it is a permanent fix. Like the Thermaweld product there is a money-back guarantee on the Thermagasket too.

When I get a puncture in a tire I don't run out and buy a new $200 tire - I have it patched for $20. Does that mean that the low-cost repair is "too good to be true" over the cost of a new tire - I don't think so. I simply have no philosophical problem with trying a low-cost fix to a problem before jumping directly to the expensive replacement option.

In the end Thermagasket may turn out to be complete junk and I will not hesitate to let everyone know if that happens. This is a truly neutral experiment and I have no interest in proving anything about the product, good or bad. What happens, happens and everyone will hear it here.

So...the next question I have...WHERE CAN I GET SOME?? I have a grand-am that has a warped head...that I'd be willing to try it with...worse case scenerio...I'm still putting a new head and/or engine in the thing...

Alrite...I answered my own question...anyone else wondering about this stuff, it's apparently ONLY available direct from the manufacturer...more can be learned from their website...

http://www.rxauto.com/index.htm

So...the next question I have...WHERE CAN I GET SOME?? I have a grand-am that has a warped head...that I'd be willing to try it with...worse case scenerio...I'm still putting a new head and/or engine in the thing...

Sorry, take a look at www.rxauto.com.

Remember - I'm not recommending this product yet, I'm just evaluating it. Robert at their tech support line is helpful - you might want to talk to him. For a non-diesel engine the kit is just $99.

Short status update. It has been almost a week and I am still taking the van for long drives every day as recommended. The engine still runs fine. No blow-back into coolant system that I can detect, water level stays constant in the resevoir, and no overheating. No rough running or white smoke at startup. Very easy engine starting.

Looking good.

You said when you flsh out the thermagasket you need to refill the coolant at a 25/75 mix. Question: which is the coolant and which is the water? And not really a question, but more of an observation- thatse very high. I though you're not supposed to use more than 60% or less than 40% coolant. Is this a normal ratio for diesels, is this another temprary step in the repair, or is this a permanent change to the way you will have to maintain your truck from now on?

OK, I had the percentages wrong. The instructions actually say, in bold letters no less, to fill it with a 30% propylene glycol - 70% water mixture. I called rxauto tech support and the recommended 30/70 ratio is not part of the fix and there are no restrictions on concentration or type of antifreeze. Why they put that particular mix in the instructions I don't know, so I'll probably make it a 50/50 ethylene glycol mix.

Thanks for clearing that up. I hope the fix continues to work. Keep us posted.

Very interesting, I may keep this in mind as well for engines that are not worth repairing but are still usefull w/o the huge bill for labor.

But, my mechanic is far too cheap (me, and free), so I look at headgasket failure as:

2x $40 Felpro headgaskets
2x $20 Box of Head bolts
5x $3 cans of brake parts cleaner
1x $12 set of intake manifold gaskets
1x $5 tube of RTV
3x $13 antifreeze
3x $1 distilled water


Time....

But, this is in a GVAN, so there would have to be some curse words involved...

WHOA FELLERS propylene glycol ??? is this right, you sure ethylene glycol isn't the correct term, and also does it matter if it's orange or green coolant, you can't mix orange and green so a full flush has to be done before that can be added as well. Will this stuff mix/work with standard ethylene blends, do you have to full flush before shifting to propylene mix.

Only reason I ask is I don't want your result to be skewed by wrong chemistry

Both propylene glycol and ethylene glycol are commercial anitfreezes. EG is the sweet tasting poisonous one, while PG is non-hazardous (in fact it is a food additive). Either can be bought as antifreeze, but EG is much more common. I did not know they were incompatible so that is good information to know.

As far as the Thermagasket is concerned, either PG or EG is fine to use immediately after the treatment is flushed from the cooling system. I was concerned because the instructions seemed to require PG after the treatment, but it was just poor wording.

BTW, I found this interesting fact: in the US 4,000 people and 90,000 animals are poisoned by ethylene glycol antifreeze every year. Thre was even a murder by EG this year.

I'd be willing to bet half of the 4,000 people tasted it to make sure they remembered to put antifreze in before winter hit...LOL...anyone know how much it takes to poison a person?? I know I've used the "taste test" before...

Very interesting, I may keep this in mind as well for engines that are not worth repairing but are still usefull w/o the huge bill for labor.

But, my mechanic is far too cheap (me, and free), so I look at headgasket failure as:

2x $40 Felpro headgaskets
2x $20 Box of Head bolts
5x $3 cans of brake parts cleaner
1x $12 set of intake manifold gaskets
1x $5 tube of RTV
3x $13 antifreeze
3x $1 distilled water


...and a partrige in a pear tree??):h

Actually there multiple flavors of EG, common green, orange (Dex Cool), and VW's G-12 orange are the ones I'm familar with none of those are inter-mix recommended, and are very specific about flushing fully before switching over to the other, chemically they aren't happy being mixed.

So before any mixing of coolants I strongly suggest any one contemplating this make sure they got the chemistry correct.

...anyone know how much it takes to poison a person?? I know I've used the "taste test" before...



NOT MUCH! Unfortunatly there is human data for this. The smallest lethal dose of ethylene glycol known to have killed a person was 3 teaspoons for a 40 lb child. That translates into 1/4 cup being fatal for a 150 lb man. That low a dose normally does not kill, but it has done.

Generally 50% of adults who drink 1.5 cups die. Note that this does not mean the the 50% who don't die are ever healthy again, or that no one who drinks less than 1.5 cups dies. EG is really dangerous stuff, especially because it TASTES GOOD. (At least in the US it tastes good.. in Europe manufacturers have to make it taste bitter.)

At last a topic on the diesel forum I know something about! I was an occupational health professional specializing in chemical exposures for many years. I may not know jack about diesels but I know my poisons! :)