Old 1998 Chevy Blazer - temperature gauge rises, then goes back down. Driver has to take it on a 3 hour trip later today. It was just in the shop for inspection 2 months ago - check coolant levels? Would that fix problem till driver gets back to town?
Yes - easy to do.
It’s possible the thermostat is flaky & needs replacement.
If the temp gauge is up and down then the coolant is likely down and there is air in the system. If the system is low, there must be a leak. It could be anywhere in the system from a hose to the heater core. However, these engines were notorious for intake manifold leaks because of the wet design. They can leak externally or internally or both. Further damage will occur to the engine if driven low on coolant or with it leaking internally. This can be up to a $600 repair if the intake is the problem.
For a necessary trip, top off the fluid and take a quantity of premix along.
Yup…instrument could just be going out. This is a cheap fix. However, the consequences of overheating are expensive and so should have it looked at.
Hello, I am supposing it get hot and then cold cycles while you drive drive. Is that right? It could be an easy problem. Of course you mentioned coolant replacement. You should have an overflow hose and conatiner so when the engine gets warm it has an overflow tank to store the coolant until the temperature returns to a lower range and it will reabsorb the coolant.
My best guess if it continues however, it is a thermostat that controls the water flow at given temperatures. fan pully belts also cause issues if they are not tight.
Let us know how it goes:)
What I know about the innards of a car can fit under my fingernail, but this is an old junker that had similar issues some years ago. I think it was a thermostat problem then and hopefully its the same thing now. I told the driver of this thing to get it checked out when they get home.
Thanks for the answers!
The thermostat is not an “instrument,” it’s the device which controls coolant flow from the engine to the radiator.
That pretty much my knowledge of such things too. But one thing I have learnt is the first sign of trouble check the oil and water levels. If either of these runs dry its most likely kind of academic what the underlying cause is, as the engine will be pretty much boned..
Is there any rhyme or reason to when it gets hot and when it cools down? If it heats up at idle or low speeds, but then cools off when you get going a bit, it could be the fan clutch (I believe this has a belt-driven fan).
The other “worth a try 'cause it’s cheap” part for odd cooling system issues is a new radiator cap. A bad rad cap can cause all sorts of weird stuff, including possibly preventing coolant from getting from the recovery tank (where you’re supposed to add coolant) into the radiator. That can make it so the coolant level looks fine at the plastic tank, but there really isn’t enough in the radiator.
What is the rate and extent of the temperature change?
Is this a continuous cycle or does this only happen once and then the temperatures seem to level out? Does it happen in a series of smaller and smaller jumps? Does it reach the same peak but the troughs get shallower?
That has to be the smallest nit I’ve ever seen picked. So small it might not even exist.
A useful trick to remember is that you’ve got a “spare” radiator - turn on the heat to full and the blower to max. You may be uncomfortable (open a window!) but the heater will pull heat out of the coolant, regardless of how well the thermostat, radiator or radiator fan are working.