I think you may be on to something here. I had an old car that showed drastic temperature swings on the gauge, too. Turns out the gauge was correct, but I found that one of the old coolant hoses (I think it was the one running to the heater core) was collapsing on itself and restricting coolant flow. Are your hoses original?
I can’t say whether they’re original or not, but they’ve been on the car as long as I’ve had her (about two years), and she’s got about 230K miles on her, so maybe that’s it. I’m really hoping that it turns out to be one of these cheap/easy things.
How about leaving the stat out for a couple of days, see how that affects the described symptoms?
I should have thought of that - it owuld definitely have helped pinpoint where the problem is.
Well, I got fed up with it this weekend and took it to the shop; I’m waiting to hear from my mechanic what the problem and the damage (cost) is.
Thanks for all the help, guys. I’ll put one more post in here once I find out for sure what’s wrong.
bauble
Well, if anyone’s still interested, it wasn’t the head gasket. Nor was it a problem with the radiator or one of the hoses (well, not exactly - turns out, one of my hoses was leaking under pressure, but that was replaced and had no effect on the problem). Or even the thermostat.
It’s the freakin’ gauge. My mechanic checked it out first with some heat-sensor and then to another input (maybe the car’s computer - I’ve forgotten already) and found that the car’s not getting over 214 degrees F, even when the gauge is red-lining.
So now I’m thinking all the grief I went through with replacing the thermostat was totally un-necessary. sigh.
bauble
Ain’t it always the way? At least you found a relatively cheap solution. And hey, you caught that leaky hose before it became a real problem.