'97 z28 cooling problem

[jeffs97z28]

Heres the symptoms, stock '97 z28, 86,000 miles, original coolant, stat, w/pump etc. system has never been opened up,

Car seems to run too hot in traffic, even in cool weather, creeps up over 210 until the fans come on, runs around the 180 mark on freeway, whats really weird is that now that fall is here I'm noticing that I'm not getting near enough heat out of the heater core. At 180 the air is just warm. I'm freaking out here, I was hoping it was just a stat stuck open but I felt what I think was the hoses to the heater core [ it was dark ]. and if I was on the right hoses one was luke warm and the other hot. Is it worth doing a flush and fill with a stat replacement or should I diagnose it further to try and determine
if 1. the stat is bad. 2. the heater control valve is bad. 3. do I have a small leak somewhere and is the system low on coolant. 4. the worst - is the heater core getting plugged. 5. Worse yet a combination of any of the above.

Any advice welcome. How tough is it to bleed the air out of the system once you open it up? If I can get past that hurdle I can probably do everything myself except the heater core if its bad.

[TraceZ]

first of all I need to say *shame on you* for neglecting your cooling system so badly. You've never even changed the coolant?

shame, shame, shame.

It sounds like it needs to be thoroughly flushed at a minimum. The heater core sounds plugged up. You can disconnect the hoses going to the heater core and use your garden hose to powerflush it out. You'll be surprised by the crap that will come out. Also powerflush the rest of the system and put in some fresh coolant.

If it were me, I'd go ahead and replace the water pump and thermostat while I was at it. You'll already be getting dirty and disconnecting some hoses when you flush it all, why not just go the extra step and replace that stuff? It's certainly old enough to warrent preventative maintenance.

also, your car does not have a heater control valve.

[jeffs97z28]

Hmmm, with no heater control valve what shuts the water on and off to the heater core?

Thanks
Jeff

[TraceZ]

Hmmm, with no heater control valve what shuts the water on and off to the heater core?

Thanks
Jeff

I've often wondered that myself. Maybe it is hot all the time, and there are doors that close it off? Hmmm.

[fastTa]

We do have an in-line control valve. It is right below the 90 degree elbow that comes off the water pump and goes to the heater core. From what I understand, it controls the flow at high RPM's so as not to cause abnormal stress to the heater core. Some people have removed it without any problems. But I cannot say that I recommend it

But, I would also flush your heater core as well.

[TraceZ]

We do have an in-line control valve. It is right below the 90 degree elbow that comes off the water pump and goes to the heater core. From what I understand, it controls the flow at high RPM's so as not to cause abnormal stress to the heater core. Some people have removed it without any problems. But I cannot say that I recommend it

But, I would also flush your heater core as well.

right, but the control valve does not stop flow when you turn off the heater. On many cars I've seen there is a vacuum operated or electrically controlled valve on the heater hose the actually closes off the flow when the climate controls are in the "cool" mode. Our 4th generations cars do not seem to have such a valve.

[fastTa]

right, but the control valve does not stop flow when you turn off the heater. On many cars I've seen there is a vacuum operated or electrically controlled valve on the heater hose the actually closes off the flow when the climate controls are in the "cool" mode. Our 4th generations cars do not seem to have such a valve.

I know, but it is not uncommon for this valve on our cars to malfunction or become clogged and prevent proper flow to the heater core and cause other cooling problems. This could be a factor in jeffs97z28's case.

[TraceZ]

I know, but it is not uncommon for this valve on our cars to malfunction or become clogged and prevent proper flow to the heater core and cause other cooling problems. This could be a factor in jeffs97z28's case.

Ah, yes. I see what you are saying now.

[jeffs97z28]

Kevin G, I think you are on to something here,l I found the flow valve and the hose on the stat side was hot and on the other side just warm, I sqeezed it a bunch of times on both sides and got better heat for awhile, now ir's back to the same problem. I'm going to have it flushed on Monday and if that doesn't clean it out, have the hose with the vale in it replaced. Another 400.00 out the window. I will report back.

[Rob B (shoebox)]

Heat is purely controlled by the mix door in the HVAC housing. Water always circulates through the heater core and there is no heater control valve like some other cars have.

I agree that the restrictor that is in the heater hose may be a factor in the clogging problem that our 4th gen cores seem to have.

[jeffs97z28]

Well I had the heater hoses and thermostat replaced and still no heat, temp guage runs normal on the road and heats up to est 215 when idleing, too hot for Minnesota in the winter.

[soCalTA]

I had the SAME problem... got worse over years and the summers here in SoCal would make it so I had to drive with the windows down and heater on. finally it let go..... turned out the water pump had been failing and the splines were worn off. So I just replaced the water pump, therm and radiator with a fluidyne. runs great ....

[Rob B (shoebox)]

Well I had the heater hoses and thermostat replaced and still no heat, temp guage runs normal on the road and heats up to est 215 when idleing, too hot for Minnesota in the winter.

Did you flush the heater core as TraceZ suggested? It is common for it to be clogged. Having a system flush done does not always flush out the core. It needs to be done by itself.

[TraceZ]

Well I had the heater hoses and thermostat replaced and still no heat, temp guage runs normal on the road and heats up to est 215 when idleing, too hot for Minnesota in the winter.

But did you powerflush the heater core?

[Maverick_82]

my area of expertise is the third generations. a major cause of their overheating was the removal of the air scoop beneath the engine compartment. even if the fourth gen didnt have this it might help a little to add it.

i also agree with checking or replacing the thermostat