Verbalkint99

Ok, so I am getting warm air through the vents but not hot. The radiator, water pump, t-stat, hoses, fan cliches were all replaced this time last year due to overheating issues.

So far I have flushed the coolant and it made no difference. Then I flushed the heater core on its own just fine. So I know coolant cam get in and the valve is working. After doing this the heat worked great, then I overheated on the way home. Checked the fluid level and all was good. But now I am back to no heat!!

Amy thoughts?

VTJeep

How well did you flush? Did you back flush?

DFlintstone

I saw on another post that there is such a thing as a 160* thermostat. Wonder if you where overheating somebody stuck one of those in there? Of course if it doesn't blow hot while your overheating.....that would be the valve or the core.

I once saw on an old Jeep valve, it had built thick deposits on the back of the butterfly. When rotated open, it still blocked 1/2 the flow.

77olds

A thermostat does not control the temperature of the engine - even if it was bad, you'd still reach normal operating temperatures at the very least.

A thermostat regulates the flow of coolant so that when the engine is cold, the coolant moves more slowly and heats up quicker - then once the engine is warm, it opens and allows full flow.

If the t-stat is stuck OPEN, then coolant is at full flow 100% of the time, meaning it will take longer to heat up to operating temp, but it WILL still heat up.

So, if you're driving short distances, maybe this is the problem - you get to your destination before the full-flowing coolant has time to reach operating temp.

If the t-stat is stuck CLOSED, then the coolant will be moving too slowly to be adequately cooled by the radiator.

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With all that in mind, since you said you overheated, and now it's not getting hot enough, I feel like you either have a blockage in the system or that there's an air pocket that needs to be purged.

I replaced the water pump on my old minivan back in high school, forgot to burp the system (get all the air pockets out by running it with the rad cap off), and even though the coolant was not hot, the gauge jump into the red after 5 minutes of driving due to a pocket of air that super heated and gave a false coolant temp reading.

Burping the system fixed it.

So, try that. Let your engine cool all the way. Take off the rad cap, start her up, and let it run. Put on some safety glasses (trust me) and watch the coolant level in the radiator - if it suddenly goes down, then an air pocket was released. Pour more coolant in. Watch it, and continue doing this until it's evident that no more air is in the system.

Verbalkint99

Thanks for the info....I picked up a new stat....figured 5 bucks and 5 min won't hurt. Most of my driving is short distances right now. As for burping, I did run it for about 15 min, and added as needed. Though I was under the impression that the coolant system on my 2000 "self burps', so I add to the bottle as needed.

DFlintstone

I've heard that before, that the temp is not controlled by the thermostat. I'm having a hard time wrapping my head around that. So towing up hill, down hill, one core or three core, 80* or 10* out, in town, or in a head-wind, the thermal budget happens to balance out around 200* on it's own. I'm not arguing! Just a little tough to understand. Granted, open is open, and better hope you brought enough "radiation" to the party!

77olds

It's like this.

You're driving down a two lane road at 55mph, there's steady traffic but you're moving along just fine.

Then one of the lanes gets closed down, and now you're creeping along at 25mph because all of the traffic has to merge into that one lane.

You coolant flows through the thermostat. When the engine is cold, the thermostat is "CLOSED", allowing let's say HALF the normal flow of coolant through it. This causes the coolant to move slower through the engine, meaning that it heats up faster.

Once the engine reaches the operating temp, the t-stat "OPENS", allowing full flow, at full speed.

The t-stat does not regulate engine temp, BUT if it's stuck CLOSED, the engine will overheat because the coolant is not flowing fast enough.

If the t-stat is stuck open, the engine will take longer to warm up, but will still reach operating temperature eventually.

If you get a 160* t-stat, then the t-stat will open at 160*. If you get a 180, it'll open at 180.

What happens past the point that the t-stat opens has nothing to do with the t-stat. You can think of it like once the t-stat opens, just pretend it doesn't exist.

The only reason you'd want to get a larger number t-stat is if you want your engine to warm up as fast as possible.

DFlintstone

So....if I'm going down a long hill on the freeway at 65 mph, with a nice dual core radiator, and it's 25* out, and I have a 195* thermostat, it wont close some, keeping my heater putting out nice? (where a 160* wouldn't till (160), and make my heater weak?)...That's hard to wrap my head around!

djb383

The t-stat controls MINIMUM coolant temp. The water pump starts rapid coolant flow the moment the motor fires up regardless of the t-stat being open or closed. The speed of the coolant flow is always determined by the speed of the water pump. When coolant temp is below the t-stat rating, coolant is rapidly flowing in a loop that consists of the block, the head and the bypass. As coolant temp reaches and rises above the t-stat rating, the t-stat slowly/gradually opens, thus allowing a slight decrease in coolant flow thru the bypass and adding that coolant flow to/thru the radiator and the coolant flow loop. The t-stat has an infinite number of open positions between closed and it's max open position.

Saying a t-stat does not control coolant/engine temp is just incorrect, because it does.....it controls MINIMUM temp.....the rest of the cooling system components, ambient temps, engine load, etc., control MAX temps.

DFlintstone

And THANK YOU djb838
I've seen posts saying the thermostat does not control the temperature.
Guess that's only when your cooling system can't bring it down.
Thought I'd woken up in one of those parallel universes or something.
Maybe I did, but thermostats still work here also. Thanks Again.

djb383

Not only do t-stats work to maintain minimum coolant temps, the FSM says do not operate the motor without one (normal operation).