I need some help. I have a 2000X 161,000 miles. In July the thermostat went bad so i replaced it and have had no trouble until about 4 weeks ago. Now when the truck is cold it warm up to the normal temp after a few minutes the temp gauge will drop and the heater will blow cold air, then the temp will spike to the red in about 5 seconds. If I pull over and let it idle for a few seconds the temp will return to normal. It wont do it again. I am also having to add coolant/water every day. I think it is boiling over from the resevior. I tried to run with the heater on and off. It dosen't matter. If the truck is not cold it wont do it. What do you think i'm dealing with. Thanks for your help.

 

I think you have a defective thermostat or one that is not of proper spec or possibly damaged or installed improperly. Just my couple o' pennies.

 

Do you recall if the new thermostat had one or more little holes in or around the valve? Thermostats without these "bypass" holes can act funny as they pretty much block all flow, allowing stagnation and/or steam bubbles to form at the thermostat. Letting just a little coolant by lets things stabilize.

Pop out the thermostat. If it presents a solid blockage when closed, carefully drill 1 or more 1/8" holea in the "poppet valve" to let some coolant flow through at all times. It may delay warm up by 10 or 15 seconds, but may eliminate the freak out.

 

That's a strange one. Does the engine really get hot when the temp gauge says it does?

 

Good question. I would be surprised if it could. This time of year, it would take several minutes to get engine that hot even with thermostat fully closed, not a matter of seconds. Hence my thought of a localized steam pocket.

 

Yes the engine really is getting hot. one time I quess the computer went to a safe mode, the low coolant idiot light came on and if felt like it was running on only a few cylinders. When that happened i stopped turned the engine off, waited a few minutes and when it restarted it ran fine. That has only happened once, most of the time i can pull over when the temp is rising.

 

Yeah but...does it really get hot? Like can you see the coolant overflowing the reservoir?

You're having to add coolant so it must be going somewhere but those conditions you stated right above this post can indicate a bad sensor too.

 

yes it really is getting hot. Last night i let it do this in the driveway with the hood open. Water will boil out of the reservior, then i guess the thermostat opens and the reservior will almost drain itself. Must be the thermostat?

 

Yeah....that's certainly where I'd look first.

 

Any chance you had a few too many beers and installed it backwards? Not that i have ever done that!

 

WestxSRT10...given your signature I was wondering if you could give me some tips on how I could afford a stable like that.

 

hummm..1 stayed married for 32 years
2 worked as a Steamfitter for 30 years
3 bought a house in SoCal for $42k sold it $645 2.5 years ago

I'm selling the 03 QC to a buddy today....wifeys sad as it was her baby

I really did install a thermostat upside down once and the symptoms matched VHOLT's.

 

Another remote possibilty, since you are adding coolant, is a head gasket problem. Have seen the temp. gauge on my old Dodge Shadow do erratic things, blowing cold air, then spiking the temp. gauge all because the head gasket was leaking. Replaced the gasket and resurfaced the cylinder head and all was well again. As was explained to me, a blown head gasket does not always leak coolant into the cylinders. In fact it could go the other way, compression is pumped/leaked into the cooling system forcing the coolant out the overflow or rad cap if the pressure is too high.

 

This one is my first guess, if not your thermostat is screwed up.

Also its rare, but a rad hose can get old and start to collapse on occasion, causing all sorts of weird **** to happen.
That happened to my old 1970 chevy truck i had when i was a young lad.

 

air bubble in the system maybe ???

have u tried to have the system power flushed and dble check that thermostat.. i bet its either in wrong or the wrong one for the application...