Idling a little warm, I think.

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thesameguy

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The '93 Southwind spent the last 16 months doing nothing, which isn't how I like it, but it's how it is. Was. Yesterday I finally had an opportunity to take it out, and the first (only) thing odd I noticed is that sitting in traffic, it gets warmer than I think it should. Here's some data I collected:

1. Thermostat seems to be fine - after ~10m the upper radiator hose starts warming up quickly and stays hot
2. The main clutch driven fan is difficult to spin when cold - give it a push and it stops immediately
3. At cold start, the main fan is spinning full speed, as expected
4. After the engine has been run up to temperature, the main fan is a little easier to push, but stops within 60 degrees, it won't spin freely
5. There is an electric pusher fan up front, it cycles normally
6. I flushed the cooling system about 18 months ago, it came out 100% clean, and it still looks 100% clean
7. When cold the overflow bottle is at the cold mark, when hot the overflow bottle is at the hot mark
8. On the road, engine temp is very consistent at ~203F at the ECT sensor (according to Tech 2)
9. Sitting in traffic, however, engine temp creeps up to 221F at the ECT sensor and it will not cool down. Ambient temp is around 60F.

To be fair, I'm not sure if this is how it's always been. Something in the last 16 months has affected the instrument cluster - the voltmeter shows 12v but my aux voltmeter shows 14.1v at the chassis battery, and Tech 2 shows 13.5v at the ECM. But the thing that caught my eye is that in traffic the temperature gauge is sitting on the border or Normal and Red, which seems like it should be ~240F but, again, Tech 2 says the actual engine temp is 220F. So the voltmeter reads low and the temp gauge reads high...

It's possible that the engine has always run at these temps, and crappy '90s GM instruments are filthy liars.

Nothing I've found indicates anything is wrong per se, but 220F seems hot, even for an iron block 454. The only thing I can actually find "wrong" is that Tech 2 says the target idle speed is 750rpm, but I'm idling at 900rpm. Not sure if that's normal (I've literally never looked before) or maybe a vacuum leak or a sad idle valve.

Does anyone have any reactions or thoughts?
 

Krazeehorse33

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Not expensive and I doubt terribly difficult to install a mechanical gauge if that would give you some peace of mind. The dash gauge puked on my 03 F250 so I put a mechanical gauge in a single pillar pod.
 

Domo

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When was the last time the radiator was cleaned - meaning the outside of the radiator, not flushing the inside. If it's all caked with dust/oil/dirt/mud since '93, then that could be the entire problem.
 

thesameguy

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FWIW over 80% of all 12V issues are the result of a poor/missing ground. That is the first thing I would inspect.

I'm not too worried about the instrument cluster - I have a Tech 2 which reads all the engine sensors through the diagnostic port. The only reason I brought up the gauge situation was to note that I've no idea if or how long they've been off, and whether the behavior I've just become aware of it new or not. For all I know, it's been idling at 220F for eight years. :) It just seems that's very warm.
 

thesameguy

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When was the last time the radiator was cleaned - meaning the outside of the radiator, not flushing the inside. If it's all caked with dust/oil/dirt/mud since '93, then that could be the entire problem.

It was cleaned at the same time I changed the coolant, and before that around 2015. It's never been dirty - we pretty much never drive in wet weather or off road. Since it stays cool in motion, I'm not prone to blame the radiator. It only seems to get warm sitting, which feels like more of a fan problem. But, I've never heard of a "lazy" fan clutch... IME they either seize up or stop engaging altogether, and mine is doing neither of those things. I'm thinking about just replacing it and seeing if that helps.

I also want to dig into the idle... maybe idling 150rpm too high is just creating a slight extra amount of heat? Seems like a stretch. But high idle should be cured no matter what. The only possible source of a vacuum leak would be the evap system, barring an intake manifold or TBI gasket failure, I suppose. I've been really thinking about putting an Edelbrock et al intake on it... maybe now is when I do that... drain the coolant, change the intake + thermostat + TBI gasket, see what happens.
 

Ex-Calif

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Go to harbor freight and pick up and infrared gun for like $10.

Shoot the temps at the gooseneck coming out of the block, the gooseneck going into the block, a metal part of the radiator near the inlet at the top and near the outlet at the bottom.

My RV sits at the redzone (~220*) while the actual top temp is like 180-190.

From top to bottom of the radiator you should see about a 20-30* drop through the radiator.
 

thesameguy

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Go to harbor freight and pick up and infrared gun for like $10.

Shoot the temps at the gooseneck coming out of the block, the gooseneck going into the block, a metal part of the radiator near the inlet at the top and near the outlet at the bottom.

My RV sits at the redzone (~220*) while the actual top temp is like 180-190.

From top to bottom of the radiator you should see about a 20-30* drop through the radiator.

I'm not sure what this proves? The sensor for the gauge is on the cylinder head, and you're measuring the surface of the water outlet, which is on the intake manifold. There is a variance in temp there... at least 10-20F. On my 350 Suburban cylinder head temp is usually 20F hotter than the radiator inlet, and I'm not measuring the surface which is probably good for 10F right there.

If your sensors are lying then your Teck2 is lying check it with an infra red gun..>>>Dan

Again, I don't think the sensors are lying. They appear accurate. Only the gauge is wrong, and I don't care about that. An infrared gun won't prove anything I don't think... surface temps are not the same as coolant temps. My concern is that I don't think coolant temp should be 220F idling. I think that's 10-20F too hot.
 

boatbuilder

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Some of your temp rise may be due to heat soak. When you come to a stop you slow down the water pump and fan but you still have the heat from running that has to go somewhere. I would bet that if you shut the engine off for about 10 minutes and then key on you will find the temp up another 20 degrees or so.
 

TheBar

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Idle speed can affect the heat because your torque converter locks up more which creates more engine drag at higher RPMs. But 150 RPM won't make that much difference. 220 is at the high end of normal but that is not overheating.
 

Ex-Calif

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Again, I don't think the sensors are lying. They appear accurate. Only the gauge is wrong, and I don't care about that. An infrared gun won't prove anything I don't think... surface temps are not the same as coolant temps. My concern is that I don't think coolant temp should be 220F idling. I think that's 10-20F too hot.
You say "I don't think..." Means you don't really know.

If you think the temps at the sensor are higher you can also shoot the temps at the sensor.

Before I would go through all the drama you plan I certainly would shoot the temps. Besides, gives an excuse to buy another tool - LOL...

You could have a sticking or fouled thermostat as well. Rare but it happens.
 

thesameguy

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I suppose I don't know, but I've never seen an NTC sensor fail in a way other than total failure, and the fact it shows ambient temps when the engine is cold, ~200F when the thermostat opens, the O2 sensor shows good values, and the vehicle passes smog I'm inclined to believe it. NTC sensors typically fail to infinite resistance, which makes the engine think it's very cold, resulting in rich running. An NTC sensor failing to too low resistance (showing too hot) would be unheard of. Even a wiring issue results in too-cold readings.

I have a pretty high-end temp gun and I do understand what you're suggesting, but in this case since I'm looking for variances inside the margin of error of measuring surface temps (~20F) I don't see how it can help.
 
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thesameguy

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Some of your temp rise may be due to heat soak. When you come to a stop you slow down the water pump and fan but you still have the heat from running that has to go somewhere. I would bet that if you shut the engine off for about 10 minutes and then key on you will find the temp up another 20 degrees or so.

That's definitely true - I'm sure heat soak is a factor here. But it's strange (distressing?) that the system seems incapable of shedding heat when it's not moving. I definitely agree it will tend to heat soak when sitting, but it still seems the fan should lock up a bit more and shed some of that heat. It's under 60F here... it'll be over 100F next year - it'll be even less good at managing heat!

Idle speed can affect the heat because your torque converter locks up more which creates more engine drag at higher RPMs. But 150 RPM won't make that much difference. 220 is at the high end of normal but that is not overheating.
Yeah, I don't think it's overheating. It's an iron block/head engine. It's certainly fine up to 240... The fan in my Fiero doesn't even come on til 235! But - to draw a lame comparison - the Fiero sits at around thermostat +15F, or 210F unless it's been sitting an extraordinarily long time or it's very hot out. The P30 is sitting at thermostat +25F and gets there within a minute or two of stopping. Generally speaking the Fiero's behavior is typical... engines run at +15F of thermostat and that's true (I think) of most cars.... Maybe worth noting that 210F is also dead-center on the motorhome's gauge. This just all makes me think the main fan is being lazy - which I've never heard of, so I'm baffled. ;)
 
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