Thermostats

[kenh]

For us guys in the northern part of the US...

What are you running for a Tstat? I e had three from Advance Auto and one from Orielies. All of them will spike the temp from a cold start to 215/220, then fall back to 160ish. The cycle continues and eventually stabilizes but it takes 10 to 15 miles of driving to do so.

Anyone have this experience?

Ken

It's a 195 stat

 

[SUBURBAN5]

I know I'm from the south. But I was running a 195tstat. On hot days at idle she would reach 210 maybe slightly higher. Once you drove around she dropped to about 180ish. Never really had crazy fluctuations like your describing. I've recently switched to a 180tstat cause the summer was getting brutal. Anyways I guess my point is just your symptoms sounds wierd

 

[Pinger]

I'm in Scotland so pretty northerly and mine gradually climbs to 210F and stays there for as long as the engine runs. What number is on the stat I don't know. The only variation is if I hoof it up (eg overtaking) and I notice more heat from the heater - but I always forget to check the gauge (the big gauge in the middle takes my attention!).

 

[stutaeng]

For us guys in the northern part of the US...

What are you running for a Tstat? I e had three from Advance Auto and one from Orielies. All of them will spike the temp from a cold start to 215/220, then fall back to 160ish. The cycle continues and eventually stabilizes but it takes 10 to 15 miles of driving to do so.

Anyone have this experience?

Ken

It's a 195 stat

Yours's is a TBI, right? My brother's '90 C1500 5.7 temp. guage on the cluster seems to move around like that while driving around. Is the cluster guage what you are going off? Or some other more accurate temp. guage?

OTOH, my '00 K3500 5.7 instrument cluster never sees anything over 1/4 mark, with a new thermostat and new temp sender (the one on the driver's side engine head that that cluster is based on.) I just drive it like that. My computer does register right at 190F when I've checked it with a scanner, which is what my thermostat is, I think;

I don't know why they ever put 2 senders on these trucks. I just don't think the cluster reading is too accurate, LOL.

 

[Erik the Awful]

When I see temperature fluctuations like that, I suspect air pockets. I haven't heard of it being a serious problem on our trucks, but I always use a Lisle coolant funnel anyways. Run the engine with the funnel in place until the thermostat opens and you'll know you're good. If you have a blown head gasket, cracked head, or cracked block, you'll know because you'll have exhaust bubbles coming out of the funnel - that's how I discovered my Suburban's block was cracked.

 

[Ricky8680]

I run the stant 195. Start up it gets up to about 215,then once it opens the stat' it stays at 195 unless I'm going up a long hill. This is with the 11 blade + severe duty fan clutch as well. In fact it was in the 20's this morning,and going up a rather steep hill for about 10 mins on my way to work,it reached 215 again and as soon as I got back on decent road dropped to 195.

 

[PlayingWithTBI]

Is the cluster guage what you are going off? Or some other more accurate temp. guage?

^^^What he said. I see my cluster gauge go up to 212 then drop to ~206 when the T-Stat opens. When I data log I see the ECM's temp is ~194 most of the time. When sitting at a light in the summer my cluster gauge will go up as high as 218 when the ECM only sees 198. IMO this is because the cluster gauge is seeing the higher temps in the head where the ECM sender is located in a bigger volume in the water jacket flowing through the intake manifold. Anyway, I have this high volume T-Stat with a high volume Tuff Stuff pump.

https://www.summitracing.com/parts/bra-330-195

https://www.summitracing.com/parts/tff-1675a

 

[kenh]

Sounds like a pretty common thing with the temp fluctuation. Yes, I'm just looking at the dash temp gauge so my temp numbers are just guesses.

Sounds like I'll just live with it for now until somebody invents a t-stat that is more accurate.

OR... drill and tap a hole for the temp sender near the t-stat.

Ken

 

[Schurkey]

For us guys in the northern part of the US...

What are you running for a Tstat? I e had three from Advance Auto and one from Orielies. All of them will spike the temp from a cold start to 215/220, then fall back to 160ish. The cycle continues and eventually stabilizes but it takes 10 to 15 miles of driving to do so.

Anyone have this experience?

Ken

It's a 195 stat

WHAT VEHICLE? Rear heater?

Common for the temp sensor in the head to read 10--20 degrees higher than the coolant sensor in the intake. The sensor in the head seems to pick up heat from the exhaust.

Any modification to water pump or the coolant bypass system? Heater deleted?

 

[kenh]

WHAT VEHICLE? Rear heater?

Common for the temp sensor in the head to read 10--20 degrees higher than the coolant sensor in the intake. The sensor in the head seems to pick up heat from the exhaust.

Any modification to water pump or the coolant bypass system? Heater deleted?

1990, C1500, 5.7 engine. Heating system is all stock.