: Dex Cool is eating the gaskets?!!!



ahanash
03-22-05, 12:18 PM
One mechanic told to me today that the red dex cool coolant (from after market sellers like Prestone) can damage the gaskets, is that true? is there a dex cool that GM makes?, is there any green silicate dex cool? any body has any knowledge about this?

The Prestone Red dex cool is approved by GM, well, did the product pass any testing?

BeelzeBob
03-22-05, 12:34 PM
One mechanic told to me today that the red dex cool coolant (from after market sellers like Prestone) can damage the gaskets, is that true? is there a dex cool that GM makes?, is there any green silicate dex cool? any body has any knowledge about this?

The Prestone Red dex cool is approved by GM, well, did the product pass any testing?

Relax.....your "mechanic" is spreading rumors...that are wrong.

True DexCool is orange and is made by Texaco. It is a proprietary product that was developed in conjunction with GM and tested extensively for many years before it was released for production in 1996. If DexCool was "eating gaskets" you would think that there would be dead cars on both sides of the road everywhere you went what with all the millions and millions of cars with DexCool in them on the road....LOL LOL Just doesn't happen. One mechanic sees a gasket failure on an engine with DexCool in it and suddenly "DexCool is eating gaskets...." Hardly.....


DexCool is specifically a NON-silicate coolant...so...no...there is no such thing as a silicated DexCool coolant. There are other "long life" coolants on the market and some (for heavy duty diesel trucks) that are silicated but anything that meets the DexCool spec and is an approved DexCool compatible coolant does not have silicates.

Use the correct Texaco DexCool or other coolant that is specifically marketed as "DexCool" compliant or compatible, mix it 50/50 with distilled water and use it with no fear of it "eating gaskets"....

The DexCool corrosion protection package is based on an organic acid technology so the coolant is acidic and MUST be diluted 50/50 with distilled water before installing it in the system. If the coolant is used without diluting or in much stronger concentrations than 50/50 it can cause problems with gaskets, seals, radiators, heater cores, hoses, etc..... That is why it must be diluted 50/50 as has always been required of any coolant.

Aurora5000
03-23-05, 11:07 AM
Can you use the Dexcool that is already premixed 50/50 ?

BeelzeBob
03-23-05, 04:18 PM
Can you use the Dexcool that is already premixed 50/50 ?


Sure...as long as it is marketed as DexCool or DexCool compatible. There is the universal Prestone coolant that is green that is pre-mixed 50/50....not that stuff.

dkozloski
03-23-05, 04:30 PM
Bbob, I keep running into references, some in scientific journals, that state that some organic acid anti-corrosion packages in ethylene glycol(not specifically Dexcool)when run in open systems where the air can get at it, start attacking everything in sight including organic gasket materials. There seems to have been a lot of work in this area in northern europe. Maybe Saab(GM) in Sweden knows something.

BeelzeBob
03-23-05, 10:32 PM
Bbob, I keep running into references, some in scientific journals, that state that some organic acid anti-corrosion packages in ethylene glycol(not specifically Dexcool)when run in open systems where the air can get at it, start attacking everything in sight including organic gasket materials. There seems to have been a lot of work in this area in northern europe. Maybe Saab(GM) in Sweden knows something.


Well...yes...there are some gasket materials that DexCool or other organic acid based corrosion inhibitors can attack...there are also some aluminium alloys that are subject to attack (ask Ford...). The system has to be designed for DexCool. That was realized years before DexCool started testing and gasket materials and such were validated with it. Even silicone beaded gaskets have to be specially formulated to withstand DexCool. Point is, that was understood and done. So...DexCool is not eating gaskets in the applications that DexCool was the OEM coolant. That is why it is not specifically recommended for retrofit into other cars or applications by GM. The antifreeze marketers might suggest this but not GM. I would never, for instance , use DexCool in a cooling system with a brass radiator or brass heater core......

Yes, I know you have a thing about air coming in contact with the coolant....LOL LOL My coolant contacts indicate that this is not that bad but I am still asking....

dkozloski
03-23-05, 11:31 PM
The whole head gasket thing has undergone a lot of evolution. Way back when it was a copper and asbestos sandwich with some copper crimped around the cylinders and other holes. I remember one Caterpillar diesel that the head gasket was a sack of o-rings; some copper, some rubber, some composition. Embossed steel gaskets came out about 1953. The first I saw was a Buick V-8. Hot rodders used a lot of solid copper wire and later gas filled copper tubular o-rings in machined grooves. Now it looks like the head gasket is just a vehicle to hold a lot of sealing rings in position until you can get it all clamped. The prices are outrageous. I remember buying an entire gasket set for $15. That won't buy exhaust gaskets today. You would think that with the headbolts stretched out about a 1/16 of an inch you could seal the head up with a gasket made out of an old shoebox and painted wih "Indianhead Shellac" like we did forty years ago.

BeelzeBob
03-24-05, 03:12 PM
Your piston aircraft engines avoid the whole head gasket scene by casting the cylinder and head as one unit, machining up thru the bore from the bottom and bolting the cylinder to the crankcase at the bottom. No head gasket failure that way.

Lots of two strokes have no head gasket. Simple metal to metal seal of the head to the cylinder backed up by an elastomeric o-ring in a groove about 1/8 of an inch from the cylinder bore to seal coolant and liquids and to act as a secondary combustion seal for what seeped past the metal-to-metal joint of the head to the bore....kind of the like the space shuttle o-rings backing up the metal-to-metal joint.

When I raced Briggs and Stratton 5 HP engines on Karts I tried making "thin" head gaskets out of shoebox cardboard and shellac and varnish and other glues to get more compression.....never was successful in keeping them in there....LOL. I did make one out of that thick tinfoil used in roast pans as my version of a "steel shim" head gasket. It worked great..... but was bumped in tech and disqualified as illegal ......the next week...LOL

dkozloski
03-24-05, 04:31 PM
Aircraft cylinders are a chrome-moly steel forging that is threaded at the top on the outside. The bore of the cylinders is nitride hardened just like the crankshaft. The head is cast and threads cut on the inside. The thread has a special rounded form rather than a "V" thread to prevent stress risers. The head is heated, screwed, and shrunk, onto the cylinder barrel. After the head is screwed on, the assembly is indexed from the head and the cylinder flange trimmed with a band saw and drilled for the cylinder base studs. The cylinder bore is actually choked at the top like a shotgun barrel as much as 0.008" to 0.010" for older engines and 0.003" to 0.005" for the newer ones. I have seen this threaded joint leak, especially on severely overheated engines. Because the cylinder is trimmed after it is assembled it is possible to rebarrel a head but not rehead a barrel. That being said, I have reheaded cylinders on antique engines where there was no other option. Years ago the Franklin engine had cast aluminum cylinders with replacable cast iron liners which lasted about 600 hrs. compared to 2000 for a nitrided chrome-moly barrel and was generally a pretty sorry arrangement. I replaced dozens of those liners.

Ranger
03-24-05, 04:35 PM
Hey Bbob, I noticed "Dex-Cool" at a local store but it has the Shell emblem on it, not Texaco. Same stuff?

dkozloski
03-24-05, 04:49 PM
During my kart racing days I had a McCulloch MC-10 with an MC-20 stroker kit. The piston protruded from the top of the cylinder and required a gasket about 1/8" thick to keep the piston from hitting the head. This engine was designed by Dr. Gordon Blair Q.U.B. Northern Ireland and was one of the first loop scavanged two strokes ever built. Anybody who knows anything about racing two strokes knows who Gordon Blair is. He designed the 170 MPH 250c.c. Yamaha twins and the Mercury racing outboards plus just about every other racing two stroke you ever heard of. He designed a 45 Cu.in. Mercury outboard motor that produced 135 HP on gas. He still does consulting work and is considered a national treasure in Ireland. In the late 1950's my buddy and I were cutting 14 second laps on the local quarter mile paved oval track with a single engine kart. I still have the engine but I built a reduction gear box for it and mounted it in a 1/4 scale F4-U Corsair RC model.

dkozloski
03-24-05, 05:38 PM
The V-1710 Allison V12 engines had individual cylinders that were held onto the head with a single big nut for each that tightened against a flange on the top of the cylinder to a torque that exceeded 3000 lbs. feet. The cylinders had a drilled flange at the bottom with studs threaded into the separate crankcase.

ahanash
03-28-05, 08:55 PM
Bbobynski! you are the greatest!

ahanash
03-28-05, 08:58 PM
Bbobynski.... how to get all the old coolant out?

BeelzeBob
03-28-05, 09:28 PM
Bbobynski.... how to get all the old coolant out?


Just pop the rad hose off and get what you can out. If you really want to go after more of it use the output of the shop vac on the fitting at the surge tank to blow thru the system to push some of the coolant in the block out. Forget about getting "all" of it. Drain what it convenient and refill with fresh 50/50 DexCool/distilled water. Remember to pop the radiator hose off and put the coolant supplement into the hose before refilling the system.

Fill slowly thru the surge tank until full. Start the engine with the cap off , rev it slowly to 4000 RPM or so several times returning to idle each time. This pushes any air out of the system. Top off the surge tank about 1.5 inches from the cap fitting and you are ready to go. Check the system when cold several days later after thermocycling several times to make sure it is still full and no more air has been pushed out.

BeelzeBob
03-28-05, 09:31 PM
Hey Bbob, I noticed "Dex-Cool" at a local store but it has the Shell emblem on it, not Texaco. Same stuff?


I am not positive but I think it is exactly the same stuff. The last time I checked (several years ago) Shell sourced their "DexCool" from Texaco who holds the patents on true DexCool. I am pretty sure that it is still the same stuff. Texaco is heavily into coolants and coolant research with the corrosion inhibitors and such and they formulate their own corrosion inhibitor packages for coolant. At the time, Shell was not into coolants, per se, so they sourced DexCool from Texaco so as to have a compatible product in their product line. I would trust Shell DexCool, if that is what you are asking.

Ranger
03-28-05, 09:49 PM
Yeah, tha's basically what I was asking. I bought some today and it is damn near the same bottle, black, says GM approved, Dex-Cool, just has the shell emblem instead of the Texaco/Havolin.

ahanash
03-29-05, 08:44 AM
I had to replace my radiator, so I put 50/50 DexCool/distilled water mix in a big clean bucket then added the tablets and mixed all, then poured it into the surge tank, I thought it was better than putting them into the hose.

BeelzeBob
03-29-05, 11:17 AM
I had to replace my radiator, so I put 50/50 DexCool/distilled water mix in a big clean bucket then added the tablets and mixed all, then poured it into the surge tank, I thought it was better than putting them into the hose.


since you were filling the system most of the mixture would go thru the tank and into the system so that should work fine in your case. To just put the pellets into coolant and then pour it into the tank is NOT recommended if the system is full otherwise. There is very little actual flow thru the tank so the material, whether in solid form or softened in coolant, will stay in the tank and settle there. I would always recommend putting the supplement directly into the radiator hose in all cases so as to expose it to the bulk flow of the cooling system. Avoiding installing it into the surge tank is the best plan for all situations to be sure.