Normal coolant temps for 7400 vortec

[Mildphil]

Hello, I have a 1999 suburban 2500 with the L29 big block, and have some strange cooling "issues". In normal driving, my guage reads at a tick or two below the bold 210°F mark. When I get on the highway, my temps are a hair below the bold 210° mark. But when I get off the highway and end up at a stop light, my temps are slightly above the 210° mark, and will stay there until I drive again and hit speed. My OBD2 sensor reports "exact" temps, but in strange increments (192.2, 194.6, 197.6, 199.9) never in-between those numbers. What could be the issue if any? Is this normal for the 454? Any insight is appreciated.

 

[east302]

I would go by whatever your scanner is reading. It should be reading the coolant temperature sensor which is the value that the computer will be using. Assuming you have a 195-degree thermostat that opens within a few degrees of that value, your readings sound reasonable.




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[BowtieBrody]

I've got the same issue on my 96 454, it reads at 210 cruising when it's up to temp, and a few ticks past 210 when idling.
Radiator **** the bed, which led to me replacing it with a NAPA OE replacement, and a NAPA 11-blade fan.
Still ran 210; I started to adjust my Scan Gauge II to the important readings, low and behold,

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Now the SG reads anywhere from 197-198 cruising, 193 idling, and as soon as I punch the throttle and get the fan spinning temp drops down to 188, while the instrument cluster gauge sits and 210 once the engine is up to temp and the thermostat is opened.

I'm sure other 7400 guys can chime in and voice their opinions and experiences on this issue,

 

[Mildphil]

Thank you guys for replying, that really eases my mind. I keep worrying about it over heating, but I feel much better now. I hope some more guys can chime in so we have a larger sample size. I also live in the south so the ambient outside temps here are usually in the 80s-90s

 

[RichLo]

Dont worry about it, 180-220 is normal operating temps.

 

[Mildphil]

Any other bigblock guys out there?

 

[Supercharged111]

All my GMs read 210 with a 195 stat. I've had an 88 C1500, 98K1500, 97K3500, and 07 Envoy with 5.3. They all read 210 while the scan gauge reads around 195. Don't sweat it.

 

[c1500deathtrap]

210 is fine, also the computer and gauge use different temperature sensors, in different locations on the block. Its really quite common for them to disagree.

 

[Mildphil]

210 is fine, also the computer and gauge use different temperature sensors, in different locations on the block. Its really quite common for them to disagree.

Oh wow I didn't know that they use two different sensors. Where are they located?

 

[454cid]

Oh wow I didn't know that they use two different sensors. Where are they located?

One is in the driver's side head, and the other is right under the thermostat in the intake manifold.

The sensor in the manifold is for the PCM, the other one is for the gauge.