radiator restrictor plates in 2004 vortex 4800 sierra p/u

anyone ever hear of a radiator that is supposed to have a restrictor plate not having one? It's cold outside here in Maine and my truck doesn't warm
up until I get going over 50 mph uphill. the temp fluctuates so much the gauge is starting to look like a speedometer! The dealer changed the thermostat twice and now wants to replace the radiator. the service manager said he remembered reading a service bulletin about this problem. is this for real?
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geezer wrote:

When I lived up north, I used to put a piece of cardboard in front of the radiator in several of my vehicles. The last time I went to Oklahoma for Christmas I had to put the cardboard in so that we could have heat. 10F.
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to keep all readers up to date: the service department had my truck all day to replace the radiator they thought might be missing a restrictor plate. Their words. They didn't get it done today and decided they didn't need to replace the radiator, just install an o ring on the thermostat. Apparently they factory assemblers left it out and the two times I got the service center to replace the thermostat they didn't notice. That makes sense to me considering the symptoms. personally I don't wonder why gmc is loosing market share. we'll see tomorrow if it works correctly, apparently there was not a correct o ring in the whole state of maine, according to the gmc dealer in augusta. ha ha " Paul " <"=?x-user-defined?Q??= Paul

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geezer wrote:

Amazing! Thanks for the update. GM has been using some sort of o-ring for the last 15 years or so.
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Hey, I knew an O'Ring. Best telephone operator on the East coast. Beautiful head of red hair and.....
Can't find an O-ring on the coast? Come on! What happened to flat gaskets? And call an aftermarket place, probably sell them 99 cents each.
--

Christopher A. Young
Do good work.
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Stormin Mormon wrote:

Many GM's use a special slotted O-ring and a flat gasket (like my car). The O-ring holds the thermo in place. Without it, the thermo flops around quite a bit and lets water flow around it. Those not familiar with GM's (like his dealer mechanics) may not have realized it needed one.
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Well said.....
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" Paul " <"=?x-user-defined?Q??= Paul

Bonneville with a 3800 v6. The t'stat housing was evidently too large and would allow the t'stat to flop around EVEN with the flat gasket. We had to modify an exhaust gasket, for strength, with a diameter slightly smaller than the t'stat-with-slotted o-ring--this gasket held t'stat in place & produced adequate heat for 1st time since new, according to the owner. s
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