Running warm.

[east302]

210 is about normal for most chevys.. it's fine.

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I must have misread his post, I had the number 240 stuck in my head for some reason. The gauge cluster temp gauge tick marks aren’t linear so accuracy wasn’t on GM’s mind when they put it together.

Is there another way to get the coolant temperature on a TBI short of a temp gun?

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[TheBeast]

So it’s at least opening, then. Wouldn’t hurt to replace it, and probably wouldn’t hurt to flush it out and bleed. In the meantime, you could try burping it in case you have air in it.

Is it using coolant or leaking? Fins on radiator are clean and not gummed up with dust and dead bugs? How’s the belt...any slipping?


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Radiator fins clean, fan has worked all day, but I don’t think it’s moving enough air at idle. But I’m not sure. I’ve checked everything I should, the inspection stuff as when I’ve had an issue like this before. But, before my 98 legacy gt did this, it was headgaskets. Also, the truck ran great up and down the hill, until summer started. I have not had this issue with her before.


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[Schurkey]

So the issue is, she gets warm, about 210-220 climbing grades, ac on or off, doesn’t matter. Throttle position and gear doesn’t matter. Then, on the down hill, back to 190, level ground about 210. Idling, standing still she sits at 220. I’m thinking fan clutch, I can hear the fan sometimes, when it’s on it cools right off, but sometimes if it gets to 210-220, it doesn’t engage. Any thoughts?

Sounds like you have a marginal cooling system. The temperature increases under load, decreases when the load reduces.

ALL the usual suspects: Failing radiator is probably #1. If the radiator can't transfer heat from coolant to air, the fan clutch will never get hot enough to engage. That's a rad problem, not a fan clutch problem. Do you ever hear the fan clutch engage? I'd check ignition timing to assure you have proper advance. I'd connect a scan tool to look for fuel trim numbers--although the MIL should light up if the thing is running lean.

What does the computer think the engine temperature is? OEM dash gauges are always suspect. (Cheap crap.)

Is the fan shroud still in place? How about the air dam under the vehicle?

Low coolant level? Contaminated coolant? Stuck thermostat?

Are those temperatures based on the dash gauge or from a scanner reading the coolant temperature sensor— assuming it’s a 96+.

What does '96+ have to do with anything?

 

[east302]

What does '96+ have to do with anything?

Wasn’t sure if you could read CTS temperature with a scanner on an OBD1.



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[TheBeast]

Sounds like you have a marginal cooling system. The temperature increases under load, decreases when the load reduces.

ALL the usual suspects: Failing radiator is probably #1. If the radiator can't transfer heat from coolant to air, the fan clutch will never get hot enough to engage. That's a rad problem, not a fan clutch problem. Do you ever hear the fan clutch engage? I'd check ignition timing to assure you have proper advance. I'd connect a scan tool to look for fuel trim numbers--although the MIL should light up if the thing is running lean.

What does the computer think the engine temperature is? OEM dash gauges are always suspect. (Cheap crap.)

Is the fan shroud still in place? How about the air dam under the vehicle?

Low coolant level? Contaminated coolant? Stuck thermostat?


What does '96+ have to do with anything?

I wish it was my STi, everything from the laptop, so much easier to rework an ecu to eliminate/tune out issues that this obd1 crap. Anywho, it doesn’t increase under load, or decrease when load reduces. If I accelerate, it will drop. Sometimes it gets hot at cruise, sometimes it doesn’t. Sometimes the fan kicks on at 210, sometimes it’s at 230, sometimes not at all. I got a fan clutch anyway, as far as I’m concerned, it’s an old part. Thermostat not yet, what I have in there, does not match what they are selling at vatozone. Radiator was replaced by po shortly before I got it, gave me the receipt and it still looks new. Only thing, and I mean only thing that is aftermarket, is a flowmaster 40 series (I hate the sound), would rather have oem.


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[TheBeast]

Wasn’t sure if you could read CTS temperature with a scanner on an OBD1.



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As far as I know you can’t. I loooooove my tactrix cable and laptop.


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[Schurkey]

So the issue is, she gets warm, about 210-220 climbing grades, ac on or off, doesn’t matter. Throttle position and gear doesn’t matter. Then, on the down hill, back to 190, level ground about 210. Idling, standing still she sits at 220. I’m thinking fan clutch, I can hear the fan sometimes, when it’s on it cools right off, but sometimes if it gets to 210-220, it doesn’t engage. Any thoughts?

Anywho, it doesn’t increase under load, or decrease when load reduces. If I accelerate, it will drop. Sometimes it gets hot at cruise, sometimes it doesn’t. Sometimes the fan kicks on at 210, sometimes it’s at 230, sometimes not at all.

See first quote. You're saying that the temperature increases when going up a grade (heavy load) then decreases when you come down the grade (no load) Then increases some on level ground (light load)

Your own description is saying the temperature is load-related. And that's perfectly normal, except the cooling system should have enough capacity to maintain closer control over temperature. I can easily believe that the temperature would increase SOME going up the grade, but not that much.

What disturbs me is that it's running 220 at idle; which indicates you do have some low-load issues if the RPM or speed is low enough.

I got a fan clutch anyway, as far as I’m concerned, it’s an old part.

I'd prefer testing it, but since you already have it, great.

Thermostat not yet, what I have in there, does not match what they are selling at vatozone.

It's approximately the most-common automotive thermostat on Earth. It CANNOT be hard to find a replacement. If you've got some kind of goofy thermostat--maybe someone else put the WRONG ONE in. In that case, installing the correct kind would maybe fix all the problems.

These are the two most-common designs:

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The photo was taken with both of them in near-boiling water.

Radiator was replaced by po shortly before I got it, gave me the receipt and it still looks new.

"New" does not mean "good". Is the AC condenser OK? Packed full of bugs, half the fins folded over?

210 is about normal for most chevys.. it's fine.

Absolutely NOT TRUE unless there's electric fans involved, which typically aren't set to run unless the coolant is at 210 or so. My '88 never sees 210 unless I'm towing a heavy trailer uphill. For awhile I had a 205 thermostat in the thing to get more heater output, and it never went over 215. The "heater problem" turned out to be a cold-air leak at the ducting for the blower motor, so I removed the 205 thermostat for a 190.

Wasn’t sure if you could read CTS temperature with a scanner on an OBD1.

As far as I know you can’t. I loooooove my tactrix cable and laptop.

Can't check CTS on an OBD I system? OF COURSE you can, along with fuel trims, knock sensor activity, time since engine started, O2 voltage and cross-counts, lock-up converter activity, and plenty of stuff I'm too lazy to type. What's available is dependent on the system design, pre-86 had less info available and slower update times, but you could get the basics including CTS all the way back to '80 1/2 on most GM computers. No promises on the MIN-T system (Chevette).

 

[TheBeast]

Yeah, but he tables available are extremely limited. There really isn’t much tuning in these, compared to my 07 STi. In the first post, what I typed and what should be taken from it, is that the problem is not prescribed to any particular action. It’s running hot is random, it absolutely does not have a 100 percent, definite action that produces the heat. As per clean, yes, it is all clean and bug free, the last six of these trucks I have owned, have never had this issue, all the way back to my first 93 suburban in 98 when I got my license. Also, those thermostats are not what is described for this truck. Oreilly, Autozone, carquest and Napa all list a completely different and much smaller t-stat for the 454 that I know is in correct.


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[Schurkey]

those thermostats are not what is described for this truck. Oreilly, Autozone, carquest and Napa all list a completely different and much smaller t-stat for the 454 that I know is in correct.

I looked up what NAPA is showing for a '94 with 454. They're claiming part number THM-531090. It's a little guy judging by the photo--but they don't list the flange diameter. The Buyer's Guide shows applications for '91--95 K2500. You say you know it's "in correct", and I agree. 'Course, I've been wrong before.

I'm fairly sure you actually need NAPA # THM-183 or the equivalent. NAPA shows the flange diameter as 2.126". That would be "the" common thermostat for GM going back to about 1935, along with some Ford, some Chrysler....even imports like Alfa Romeo, Jaguar, and Austin used that 'stat.

 

[studigggs]

had a similar issue in my '90. In the desert as well and would idle at 220 w/ AC on or off. With AC on it would keep creeping up, so I'd always turn it off. Ended up being the fan clutch which was original (even though it 'tested' fine). I went with a Hayden Severe Duty and swapped to an 11 blade fan in place of the 5 blade on my '90. Now when the temp hits ~210 I can hear the fan engage and temp drops down below 210 fairly quick. AC on or off doesnt matter. Been 110 this week and I'm never getting above 210.