help

[93punow]

I have a 93 6.5td when i first drive it it heats to normal temp and then in starts to overheat. I drive for a little while and it goes back to normal this happens off and on. the heater blows hot then cold air any ideas?

[93GMCSierra]

low coolant level?, or bubble in the cooling system.

[daustin]

Sounds like the thermostat is sticking a little. Replace that and see what it does.
Don

[JohnC]

Sounds like an air lock in the system. Check the coolant level and try bleeding the thermostat housing while the engine's running. If it comes back, you could have a head gasket failing.

[Robyn]

This sounds like a low coolant issue.

Check and make sure the coolant is to the proper level in the bottle on the firewall.

Once the level is proper run the truck and see if the issue reappears.

If you are still getting hot and cold from the heater check the overflow on the coolant tank to see if there is blow over.
If you are getting blow over then you are probably in the early stages of either a leaking head gasket or a crack in a head.

The water pump could be an issue but usually they either work or not.
Even with a sticky stat you will get heat all the time.

Coolant level then go from there.

Let us know

Robyn

[rustyk]

It surely sounds like a low-coolant issue, or air entrapment; however, the air should bleed off into the overflow tank unless the coolant level's too low to retrieve it into the system as it cools. I'd look to that before messing with the thermostat/s.