To whom it may concern:

This letter is a "Thank You", for a remarkable product that was devised to rectify the problem with the Northstar engine that was plagued w/ the blown-headgasket syndrome. In short that is exactly what I had in my 1999 sls, that I had bought 3 years earlier w/27,000 original miles. Well it shook me to find out that I had a possible blown-head gasket, and the price for a new head-gasket was getting up there and so I went to Cadillac Forum and discovered Thermagasket, and so I decided to give it one last hope and your product did it. My mechanic was totally blown out of the water. He didn't believe it at first, but he believed it after he put 100 miles on my car and the engine didn't overheat.Whereas before you could not drive the car more than ten minutes without it overheating.

I'm a sort of skeptical person because of current affairs that are happening in the world, but in short I'm glad I took a chance with you. I just hope Thermagasket is a long-term fix. It's amazing that the engineers at Cadillac did not foresee this problem.

In short, I just want to give you my heartfelt thanks for a great product. To everyone out there that has the same problem with your cooling system, this product really "DOES WORK".

Dwight A. Clark


More than 9 months ago, prior to using Thermagasket I could not drive this car farther than 5 miles without severe overheating, I had spent over a thousand dollars in parts and labor to "fix" the problem at a dealership. Sensors, crossover pipe, thermostat, etc. no help at all. Bought Thermagasket kit for Northstar, installed and treated in appx 2 hrs. Has not overheated one time in more than 12.000 Miles!!! It is like it should be!

Thanks so much!!!
Phil P


I bought a cream puff of a 1998 Cadillac Deville. Only 117K on it. The original owners son was selling it, but it had overheated he said. We test drove it, bought it and drove home some 50 miles. No issues with my wife driving 40 miles round trip to work. Then I drove it for a short trip and it overheated. I thought it was leaking from the heater hoses and my big Fred Flintstone hands wouldn't fit in that little area so I took it to a well known Caddy repair shop in North Atlanta. System pressure tested fine but the hydrocarbon test came back at 750, ZERO is normal they said. $3700 to replace the head gaskets, ouch. I started researching and no one seemed to have the true FIX. was the real place, sent email and actually got a response and they told me to call them. Really, a true customer/technical support person? I talked to Dave and got the Northstar kit and FOLLOWED the direction, you don't know how hard for me that was. The wife made sure I read and re-read the directions. It took my Deville 65 minutes to get all the anti-freeze out. I did everything the direction said and off on the first drive I went with cell phone in hand. Nothing, no overheating, no stalls, no water leakage. WOW is all I can say. The Jeep video seemed like a farce but it was true!!!! I have seen 3 Cadillacs on the side of the road, overheated, in the last 2 weeks and I stop and tell them, "RXAUTO.COM"

Ernie, a true ThermaGasket believer.


My 1998 STS (179,000 miles) starting losing water out of the exhaust. I tried two other brands of advertized "Northstar" sealant. Both did not work even a little bit. I became acquainted with Thermagasket via a Cadillac Forum. I bought the kit, installed it, and it worked perfectly. It is the most effective auto repair expenditure of my 77 years.

Claude R


I would recommend THERMAGASKET to my mother, and here's why. I own two DeVilles, a 1995 and just bought a 1999. The '95 stopped running and it's a relatively minor problem yet I am unwilling to spend another dime on it. I'm a Communications student in Houston, Texas but I live 50 miles from campus. I have classes five days a week. When I got my financial aid this semester I looked on Craig's List and found the 1999 DeVille for $2,000. Of course the seller lied to me about the condition of the car and even changed out all of the liquids so the unsuspecting buyer would not detect the blown head gasket. Instead of taking my friend with me who's a Lead AutoTech for Northside Lexus of Houston I figured I could check it myself.

When I got there I pulled the dipsticks and checked everything I could get to. I drove it and it ran like a Cadillac is supposed to-smoothly and powerfully. There was a minor problem with the reservoir tank and the seller put the car in the shop to have it patched and took off the price of a new tank from the selling price. I was between classes so I went back to class while it was in the shop. The seller delivered the car that night, about ten blocks from my house. When I got in it I didn't make it two blocks when every warning in the information center that could come on came on: battery not being charged, change oil, service engine soon, theft system problem... I tried to call the seller right then and he wouldn't answer the phone. I filed a fraud complaint with IC3 and have not heard from them, but the plus to that is I filed it as soon as I knew there was a problem so there is an official record that there were major problems with the car when it was delivered to me (which is totally contrary to the ad they ran).

Because I want the car I took it to an accredited repair shop near my house who also does vehicular investigations for the DA's office for diagnostics. Not only was the head gasket blown but there was definite evidence that the seller had tried to pull engine sludge caused by the bad gasket up through the heads like they tried to suck it out or something. The shop's recommendation was to replace the engine which was going to run between $4,800 and $7,200. That was out of the question.

I was online looking at something totally unrelated when I ended up at and read a thread where several posters wrote about THERMAGASKET. I began doing my due diligence and I could not find one negative post about it. So then I called people I know who work on cars. EVERYBODY told me, "Do not to put that s@#t in your car. Fix a head gasket with some s@#t in bottle that you can pour into the radiator? Yeah, right..." EVERYBODY. But what do I have to lose? That was my question.

So I bought THERMAGASKET and my wife and I followed the instructions as if the planet was going to explode if we got it wrong. There was no getting it wrong. Like I was told by THERMAGASKET's Tech Support, "If you can turn a screw driver, and point a water hose, you can apply it yourself." It was an easy fix. We did it, and took it for the first drive and it puttered to the stop sign-I live on the corner the sign sits at. From there we drove it for five miles...

And now I drive it 100 miles round trip five days out of the week. I have a habit of setting the cruise control at 85mph. It runs cool, smooth, and powerfully. Just like the Cadillac is known and famous for. If you have a blown head gasket, make the order for THERMAGASKET. $265 beats $4,800 to $7,200 in way you look at it. One of my classmates has a blown head gasket and I told her about THERMAGASKET. I lead her to the Fountain of Fix, but I can't... You know the rest.
Thanks. THERMAGASKET helped me more than people know.

So Jannie (that's my mama). If you blow your head gasket let me put THERMAGASKET in it. It works as advertised.

Larry Smiley-El
Inside Job Enterprises



Your tech support rep Dave is an unbelievable troubleshooter. I own a small 2 Bay shop in Wisconsin. I called because I had a question about one car we were working on. After speaking to Dave I figured I would throw some symptoms of a completely different problem ( Nothing to do with head gaskets ) that we have been stumped on. He immediately without hesitation gave a couple of suggestions and opinions of what might be the problem, and he was absolutely correct.

Dillon H


Kirk, a note to tell you about my experience with your product, my 2000 deville with 119,000 miles would blow enough coolant out to overheat in 15 to 20 miles. After your treatment I have approx. (still going) 25,000 miles and it has not overheated one time! I was as big a skeptic as there is and a mechanic for 40 years, I was sure I would be calling for a refund instead of sending this endorsement. I'm now a believer. Feel free to use this note as you see fit.

Thanks again,

I used Thermagasket according to the instructions and it worked! I've put about 1200 miles on the car since the treatment and it hasn't lost one drop of water or been above normal temperature no matter how hard I pushed it. I've got my car back! You guys ROCK! Thanks for your product!

Donald Ball
2000 Cadillac Deville


I just wanted to write in and thank you for putting out such a great product.  My car started overheating last year and since then has been barely drivable for any distance greater than a few miles.I researched around looking for a "quick fix " and happened upon your website. I called in asking for more info and was immediately connected with a knowledgeable member of the staff who assured me that Thermagasket would work on my 2000 Caddy Seville. My order came promptly and installation was a breeze. After the flush of the antifreeze and addition of the mixture provided, I took the car on the first ride (as stated in the instructions)...after 10 minutes I couldn't believe the car was not overheating.  That was 2 weeks ago, and I have since put 300 miles on the car without a hiccup. The engine stays cool, it's no longer using up coolant and I can finally drive it without fear of overheating.  I recently took the car on a 35 mile trip (70 total) on a warm day with the AC running.  The car stayed as cool as ever. I am completely sold on your product and will recommend it to everyone I know. Thanks again for putting out such a quality product. 

Steven Muller


I can't thank you enough for your product. Not only did your product cure my head gasket issue, the oil is now normal in appearance and the temperature is a consistent 196 Degrees...unbelievable. My support tech was Kirk and he is awesome. Not only was the head gasket bad, there were underlying cooling issues which no mechanic could figure out. Kirk walked me through the steps needed to control the cooling system, which was also needed after the head gasket was repaired. There were times when I was ready to give up but Kirk gave me the knowledge and confidence to keep with it.  Kirk was there for me no matter when I called and I never felt I was a "bother" fact, Kirk was enthusiastic and shared his knowledge with me as if I were his very own brother. I had just purchased the 99 Deville in Sept, 2009 and had problems from the start,  had many things repaired but I could not control the temperature...I found your web site, along with some others, when I did a Google search for blown head gaskets. I was impressed with your customer write ups and felt Thermagasket would be my best option...not only did the product work as stated on your website, the customer service provided by Kirk was unsurpassed. I am telling everyone I know about your product so they will know there is hope when they have these problems, especially with the Cadillac Northstar Engine. I am very thankful for your company and your staff..May God Bless you all...

Sincerely, Mike D (Pennsylvania)


My 2001 Cadillac Deville overheated and I changed the thermostat because the gasket was distorted, I thought I found the culprit. But it did it again, so the pump was next. It then took awhile before it overheated. The upper hose was hard, excessive pressure, no mixing of oil, and at this time, no white smoke. Then the excessive pressure ruptured my radiator. It was during the winter so I kept coolant in it, but the engine froze on me and pushed out the freeze plug and destroyed the drive pulley, belt and tensioned. I  then replaced all those components and tried a competitors products and it didn't work. So now I was between a rock and a hard place. Do I change the engine, ($5000) or junk it. By this time a little white smoke was being noticed. I then came across Thermagasket. Talked to Kirk, ordered the Cadillac Northstar Kit, followed the instructions, then, O M G ! The kit worked, Usually I don't believe in fixes in a bottle being a mechanic for 15 years. Now you know why I would not give up on the car. I couldn't let it beat me, and Thermagasket helped me win the battle! This stuff REALLY works! Thanks guys! I'm a believer, e-mail me if you don't believe.

Alonzo Brown
(Email available upon request)   


My 1997 Cadillac Deville was diagnosed with a blown head gasket in cylinder. Overheated in 15 min. 2 Shops diagnosed the problem, but refused to work on the Northstar Engine. Cadillac wanted a minimum of $5000.00 to replace the head gaskets. After installing the Thermagasket Northstar Kit we have put over 4000 miles ( With several trips over 500 continuous miles ) with no problem at all.

Thanks Again!
John C


Just a word of thanks. My Deville had been in the shop on and off for 3 months parts replaced. Radiator, Waterpump, Idler Pully, Thermostat.$1275.00 later nothing changed car still overheated after 15-25 minutes of driving. I called you guys and spent about 5 minutes on the phone, you helped me understand my system was not circulating due to the leaking head gasket. I purchased and installed your Northstar system and now my car runs at a consistent 198 degrees. I was ready to donate the vehicle, now I am looking for Cadillacs with overheating problems to buy.

Tyrel C
Washington DC


I was looking for a way to fix the head gasket with out taking apart the motor.   I had talked to several shops and found that most said even if they do the work that it may or may not fix the problem.  After hearing this I started looking for other ways to fix this.  I have never believed that there was a fix in a bottle. After talking to my wife and going through this with a 2000 Deville I was not looking forward to finding a shop to do the work.  Besides the last time I had a northstar motor fixed it only lasted about 6 months or so. So we talked about trying this and I figured anything was worth a shot.  I was not going have all the work nor spend the money on 1997 sts with 231,154 miles on it.  So we ordered the product.  It came in the mail and when I opened the box my first thought was that's it where's the rest.  I had talked to Kirk when I placed the order he had told me to make sure there was nothing in the system but water.  So we were ahead of the game when it came in. I replaced the thermostat with a new one.  I did what they said, and followed what they had to the letter. I took the car to town.  Going to town and back is about 78 miles round trip.  It was 98 degree's out and I thought well we will see. At this time I would have to say holly molly I had never thought a fix in a bottle would have worked.  So I would say this my hat is off to the guys that came up with this stuff.

Thank you,
Craig Bautista
Owner of Fearless Installations.

"I can say is WOW . As a former owner of a smog station and auto repair shop for almost 10 years in Sacramento and a car dealer for longer than that I can almost assure you that I was your biggest skeptic. As of right now the thermagasket product is a perfect 4 for 4 including: 96 caddy DeVille Northstar engine, 94 Seville Northsar, 98 Chevy cavalier and a 96 Mazda Millennia S. The most unbelievable one was the 96 Northstar where water actually poured out of the oil pan (i drained 15 quarts out of the oil pan) and smoked more than a national boy scouts convention learning how to make fire and send up smoke signals but after 15 minutes the car 100% sealed up and now not smoking, overheating, missing and no apparent breach in the system at all. THANKS KIRK FOR THE MIRACLE 'SNAKE OIL'!



Hello all at RX auto:  just a quick note to let you guys know that your product worked. I want to thank you for the excellent tech support and all the help you have given me over the past few weeks. All the information about drilling the holes in the thermostat and installing the adjustable fan switch really helped.  Trust  me when I say, I had my doubts about anything helping my North Star. I figured it was a goner for sure. I tried every thing on the market at least once and most of them twice and nothing even came close to helping my Caddy from over heating. It got so bad I couldn't go 3 miles with out needing to stop and add water. The first time I tried your product I never made it around the block before a hose came off and I lost all the water, I didn't tighten up a hose clamp, my bad. So I put the second half of the treatment in and everything seemed OK and then I took it on the freeway and pushed it a little to hard and it overheated, my bad again. So I called you guys up and you gave me the option of a refund or a re treat with no questions asked. I opted to retreat and I did everything you told me to do and low and behold it worked. I drove the car around town for a week or so and then drove it non stop 1,350 miles from Long Beach Ca to Post Falls Id in 19 hours 30 mins at the avg speed of 67 mph.  So to make a short story long the stuff works it really works. If you want to give my email addy out to any body that doubts your product I will be glad to talk with any and all who would like to ask me any questions. If you can use this email in any way to help others in the same situation I've been in please do so with my blessings..

A million thanks,
Ren Swank
( E-Mail Available upon request )


Was very skeptical, but after being quoted from $3000-$4500 to replace the Head Gaskets  I would give it a try. This has got to be the best $ I have ever spent! I was unable to drive 10 miles before engine started to overheat. I followed the instructions and the car runs like new. Fantastic product!

Andrew A 1997
Seville SLS 4.6 Northstar


Hey Kirk,

Another rave review for Thermagasket.  The product is truly amazing .  My 97 STS with only 99k miles on it was about to be dumped.  I was looking a blown head gasket repair bill of $4000.   When the first treatment didn't work when my mechanic tried it you politely gave us a return authorization for my money back, but I still had half the treatment left.  After getting phone coaching from Dave and you, I thoroughly flushed the engine four times over two days and proceeded with the treatment and took the car out following the instructions regarding the rpms and driving schedule.  I went farther and farther with each trip with no overheating at all.  I then took it to my mechanic and he ran the engine block test (with Engine Blok) with the outcome showing absolutely no hydrocarbons in the coolant.  Before Thermagasket it had 220 ppm of hydrocarbons in the coolant and had turned the Blok Test yellow in 30 seconds!  The car had been giving malfunction codes for cylinder #1 with the engine light coming on.  Now the car runs like new with no engine light or malfunction codes at all. Those who doubt Thermagasket are destined to spend a lot of money for needless repairs.  With a money back guarantee, there truly is nothing to lose. I've already spread the word to a few friends who have coolant or block leaks, and I just ordered another Thermagasket kit for my daughter's Saab that is losing coolant.
Thanks for a great product and great customer service.

Mike C.
Hampton , NJ

"Your products are awesome. Fantastic results for My 98 Caddy. The thermostat 
stuck while doing 80 MPH on I-40 and the car overheated. Estimated repair was $3200.00. Savings = $2770.00. It has been 5 months and 5000 miles and it is working great. Arkansas summers can get up to 100* and it survived. Thanks for helping me save money and continue using a wonderful automobile that otherwise might have been \"put down\". We love the 98 Caddy and your products.  Anyone with a 98 Northstar needs to immediately install a New thermostat in the car to help avoid this disaster."



"Your product is fantastic! After changing the oil/filter and flushing the cooling system eight to ten times, I filled the cooling system near full and let the engine reach normal operating temp. I then added the Thermagasket as instructed and guess what? The white smoke stopped instantly and after 15 minutes of engine running at 2000rpm, I let it idle awhile before I turned it off. Since that day I have become more and more confident that this is a treatment that actually repairs! Thank You so much! I will and already have recommended your Thermagasket to others!"



"Just wanted to say I used Thermagasket on my Northstar and it worked great!!!  Add another notch to yer belt! Thanx for saving me money!"



"After talking to a couple of mechanics and being told I would have to pay almost $2000 in repairs I started researching on the web and found Thermagasket.  I called the company and immediately got a live mechanic who answered all my questions in regards to the product.  Shipping was very fast - two days!!  I called and spoke to a mechanic while doing the process and was always treated like someone who was worth speaking to - this matters because I am a woman!  No offense but most mechanics don't treat us like we have a brain.  This company is great and has the best customer service I've ever dealt with."

Thank you


"I purchased your Thermagasket for my 99 Cadillac Deville. I was a bit skeptical because I had already tried some other products that didn't help, but.Being faced with a quote of $3600.00 to replace the heads I figured why not give it 1 more try. I placed the order over the phone and the salesman I think his name was Kurt, asked me a number of questions regarding the symptoms of my vehicle. He even had us check a few things before he would take our order, he also recommended I call technical support once I received my package because as he put it "Northstars are kind of tricky to repair sometimes" The extensive knowledge the tech support rep had about my vehicle was amazing, he took the time and walked me through the process. Answered all my questions without skipping a beat over a period of 2 days. I repaired my car last October and its been running like new ever since. Your product is amazing, but your customer service and support are second to none."

Richard B
Fort Worth Texas


" I just wanted to say how thrilled I am with Thermagasket. I bought some last December for my 2001 Cadillac (Northstar) which had a blown head gasket. It has been running fine for the last 5,000 miles with NO overheating!
I just got the 2nd shipment in the mail yesterday. Even though my engine shows NO signs of overheating, I have been keeping a 2 gallon container of water in my trunk...just in case. I also decided to keep an emergency supply of Thermagasket in the trunk for added peace of mind. That is why I predered that 2nd shipment."

Mike Barilone


"Thanks for your product Thermagasket. My daughter's 1996 Cadillac Seville had a
blown head gasket with overheating, exhaust fumes in the coolant and oil in the coolant(Radiator). Applying Thermagasket solved the problem within a few miles of driving, and she has now driven the car for eight months and several thousand miles without and problems." 

Harvey M
Beford MA


"I purchased your product to use on my 1997 Cadillac Deville with 140,000 miles.  I checked with the dealer and was told that the cost to repair the head gasket would be between $3800.00 and $6500.00.   I read about your product online and thought I would give it a try.  I was amazed that within 10 minutes the steam was gone and the engine ran like it was brand new.  I have been driving it for over 8,000 miles and still no problems. All I can say is THANKS for  developing a product that actually works."

Jim G
Perrysburg, Ohio