cooling system

my 2001 oldsmobile silhouette,, 3rd time returning to dealer for no heat they changed the blower motor,thermostat, when the car runs at high rpm the temp gauge goes down and i get heat as soon as you go to idle cold air again, tried bleeding the air via two bleeders top of water pump and on other side near top radiator hose still cold anyone have any ideas also anyone hear about the dex-cool problem with gm i heard the dealer recalled the coolant for some years and models any help would be apprec.

Too Bad Steve, open up your wallet and pay the dealer the $1200.00 so you can go back to him in another month for the same problem. Good Luck!

Sounds like you have an air pocket in the cooling system. You need to burp the system. One way I've down it is lift the front end of the vehicle with ramps, jacks, whatever and attached a 2liter soda pop plastic bottle to the radiator with some tape. Fill the bottle half way with water or anti freeze and start engine. Put the heat on and watch the bottle. Do not let it go empty. Rev the engine at different RPMs. You want that soda pop bottle to be the highest point in the cooling system so the air can escape.

Any luck in fixing the problem I have the exact same symptoms on my
2000 silhouette and the dealers does not seem to know what he's
doing, next step he want to change my head and intake gaskets.

Check the oil and see if there's any white frothy gunk in it (looks like dirty mayo), if so it's a head gasket, if not it could also be the head gasket.
As others have said it is often an air lock in the upper portion of the cooling system. Bleeding the system should work, but if there is a combustion chamber to water jacket leak you get little bubbles of combustion gasses(exhaust) in the cooling system, over time these block the cooling system again, and you get no heat.
Do you see any small bubbles or foam in the recovery tank, there's just no way for air to get into the cooling system unless its just been drained and refilled, or it's being introduced from somewhere in the engine. Any bubbles showing up in the coolent recovery tank have got to come from somewhere.
If the coolent recovery tank is empty or if there is a crack or split in the line running from it to the engine as the coolent cools and contracts it could suck air into the radiator instead of coolent. Over time this could displace some coolent, the air could be picked up by the circulating coolent and left in pockets in the engine to form air locks. Make sure your recovery system is in good order.
If your recovery tank has fluid in it and the hose from the recovery tank isn't cracked or broken then try bleeding the air with the two brass bleed screws -With the engine idling and warm use a wrench to open each about a turn (watchout it's hot) until a steady stream of coolent flows out. The air is now blead out of the system, you can try it again in a day or two to see if there was any additional air.-
If you keep getting air in the cooling system, or if you temperature guage moves up and down rapidly (within a 10-30 seconds) you probably have air or exhaust gas in the system.
I've had some luck with Alumaseal as a stop leak, try the procedure I outlined to risingernicole in the previous post titled "Head Gasket".
See ya
94

I don't have any froth in the oil, only my beer. I do use mobil 1 if that makes a difference with the synthetics in the Dexcool I do not know. The Olds in in the shop now. The mechanic says that the original intake manifold gasket is plastic the heating and cooling and the expansion and contraction cause the gasket to leak. The new gasket used a felt so it will seal better, He has replaced a lot of these gaskets once but has yet to see a repeat cycle. He does recomend using Dexcool as the new coolant , this isn't the cause of this problem. He is a good mechanic and I trust him completely.

Ok, I got the 1999 silhouette with 54,000 miles on it back from the mechanic. He did show me the old gasket, it is a plastic frame with grooves in it for a rubber O ring style gasket. The problem is the constant expansion and contraction of the aluminum engine parts and the gasket fails to seal anymore. The coolant did get into the oil and the mechanic did say it was a bit frothy. While he had it apart he checked the plugs, the front spark plugs were good but the rear ones were shot, this may have been caused by the coolant getting into the cylinders. Total for the Labor was $700. and for the Gasket was $100.
The new style gasket is felt and a silicone sealant applied to the engine material.