: Coolant problem - please help!!!

05-01-04, 11:43 PM
Purchased a 1999 Seville STS. When taking delivery, I noticed that it had GREEN coolant instead of Dexcool. I was confused and asked the salesman why did it have the wrong coolant? He did not know and I assumed that I would just change over to Dexcool as soon as possible. Now I read in previous posts that once you use the green coolant you should not go back to red because the additional protection properties of red coolant will not work. What should I do? Also, can someone refer me to a link on how to flush and change coolant. Thanks - seam4

05-02-04, 02:35 AM
After you change back to Dex you will need to change it every 2 yrs or so, just like the green. It will not last like it did before becoming contaminated and apparently there is no way to undo or flush the contamination out.

I would still change it back to Dexcool though, just to eliminate any confusuion in the future.

You can do a search for "cooling system flush" for info on that. Pretty well covered I think.

05-02-04, 05:07 PM
Really you can either keep the green conventional coolant in the system or switch back to DexCool. Either coolant provides excellent corrosion protection along with the normal anti-boil/anti-freeze insurance. Once the system is contaminated with the silicates from the conventional green coolant the long life corrosion protection of the DexCool will be negated and it will need to be refreshed every 2-3 years/24-32K miles just like the green stuff.

Changing back to DexCool would eliminate any confusion but as long as you have the car and control the service of it the green conventional coolant will work fine. Simply draining and refreshing with a refill of fresh 50/50 coolant/distilled water is fine.

If you want to change back to DexCool I would drain the system at the lower radiator hose and possibly use some compressed air to push as much coolant out of the engine and the rest of the sytsem as possible. Refill thru the pressurized surge tank with fresh 50/50 DexCool coolant/distilled water. Run it for several days/weeks/months this way and then just do the same thing to get the majority of the green coolant that might have remained in the sytem out. It is better to just do drain and refills like this to minimize and dilute the remaining coolant in the sytem than to try some extreme flush or introduce plain water into the system.

When you refill the system, refill slowly thru the pressurized surge tank. When the tank if full, start the engine and rev it slowly up to 4000 RPM and back to idle several times to push any remaining air out. Refill the surge tank to about 2 inches from the cap fitting and put the cap on. Check it cold again several days later and top off if necessary. No special purging or venting procedures are required.....just rev it a few times to clear the system of any air.

05-02-04, 07:41 PM
Thanks for the responses. I was going to change over to Dexcool, replace the Tstat and purge the whole system. Knowing that I won't get all of the green stuff the first time, I was going to use one gallon of Dexcool on a refill after a complete flush. Run it on the driveway with the heater on to get new stuff through the heater core, then drain everything. Refill with Dexcool and pellets, topping off as described above. Let me know what you think. And again, thanks for your input.

Additional questions. I have a drive train problem that can use some diagnosis. The car vibrates when it accelerates. When I shift from Park to D to R, there is a significant shudder in the car. 1st to 2nd shifts sometimes take longer than they should. I know that it needs new plugs and wires, as it does not idle smoothly. It also needs tire balance (and new tires - any suggestions) - when I shift it in N on the highway, there is still some vibration, but less then when in D and accelerating. When the air conditioner compressor cycles when crusing on the highway, I can feel it through the car much more than any other car I have had. I have a 1997 SLS and now a 1999 STS. The 1997 runs better at low rpms and shifts flawlessly. The 1999 has much better suspension but does not run as good at low rpms. Throttle response at low rpm is poor. When I get into the car for the first time, the throttle sticks. Does the throttle body need to be cleaned? Depending on how much I need to spend to fix it up, I might not own it for long! Any comments would be of help. I'll try to do the plugs, wires, and throttle body cleanup, but I would like to go to the Caddy service dept. knowledgeable as possible for the other problems. - seam4

05-02-04, 08:45 PM
The coolant will circulate thru the heater circuit all the time so it is not necessary to turn the heater on while running to get the heater core circulating.

I would premix the coolant 50/50 so that you know what is in the system and don't purge the system with plain water....just drain as much as possible and refill with the 50/50 premixed coolant.

Don't know about the shudder. May be a miss and maybe the new plugs and wires will help..??? The Delco dual platinum plugs are always the best recommendation for plugs and using the OEM wires insures no problems with electromagnetic interference with the electronics on the vehicle.

Remember to put the coolant supplement pellets into one of the radiator hoses....NOT the pressurized surge tank. This is important.

Not too unusual to feel the AC compressor cycling like that....

Cleaning the throttle body will fix the throttle stickyness. Search using the search feature of the forum toolbar for more info as throttle body cleaning has been discussed many times before. Easy to do yourself.

05-04-04, 08:43 PM
Thanks for your responses. Ordered plugs, wire set, t-stat and gasket for weekend project. I'll report back how it went. - seam4