ok this isn't on a camaro - its a gmc jimmy , just got it and noticed that the temp guage will go all the way up to about 240 then drop to about 160/180 on the first cycle. then hover around the 200/210 mark , which seems a little high . when i was first bringing it home it had a snowplow attached , i thought it was due to lack of air flow through the grill( it even hit 260 once before going right back down to 200 range) but its still doing this with the plow off(240 the highest w/o plow) i m figuring on replacing the thermo this weekend , btu if that dont work ive got a water pump i can put on it . just wondering if im headed in the right direction

 

Sounds like a thermostat, probably has the stock 210 in it. Probably a good time to flush and replace the coolant also, if you don't know how old it is. Good idea every couple years, since it breaks down.

 

sounds good . im gonig to get a 180 and see what happens , guess i just dont like to see the tmep needle going that high!

 

I have a 91 GMC Jimmy with 4.3L V6. There is a quirk to these trucks with the temp gague- it reads really high.

Mine with a 180* thermostat will regularly get to 215* before the stat opens and it pluges back down. Now here's the strange part- the gague will work it's way back up to an indicated 205-210* operating temp under constant cruise conditions. It is not, in reality, running hot. I know becuase I've hooked up a scan tool and confirmed it's really running at 185-190*. And I've towed a boat in 100* weather with it- no hint of overheating. Stranger thing still is..... the dash gague reads LOWER in hot weather than in cold weather!

By now, I was seriously scratching my head. Long story short the answer is that the temp sender for the dash is located in the cylinder head, right between a coupla exhaust ports- an area that is a known "hot spot" in the head AND it doesn't get much flow past it unless the thermostat is a fair ways open. Normally in cool weather, under light load and whenever the engine has yet to get up to temp, most of the coolant just goes out the tube to the heater core (at the REAR of the block) which isn't anywhere near the temp sender- hence, very little coolant circulation past the sender. It's only when the thermostat gets open quite a ways that there is sufficient coolant flow past the sender that it reads accurate average engine operating temp- otherwise, it's always high.

Now your bump up to 260* before the stat opens has be worried. Mine's never gone over about 215-220. I'm thinking you may have an actual cooling system problem, but I doubt it's something as simple as a stat.

Just wanted to let you know about a quirk before you pull your hair out or throw a lot of money at it. I personally spent some bucks replacing..... well, everything, actually, trying to get a damned stable, accurate reading from the gague. Can't be done. I have since run into several other people with the same vehicle that have the same situation. It's the nature of the beast.

 

well i havent gotten a chance to do anything with it yet , bu tim definatly not going to put alot of $$ into it seems fine as long as its moving . the only time it hit 260 , i shut it off for a minute or so , and when i started it back up it dove right down to 210 , oh well , its only gotta last until march

 

well i think i got it . replaced thermostat with a 180* , let it idle to get up to temp , then let idle for about 1/2 hour not once did the needle go near 210 . so , hopefully this solved the problem i guess ill find out on the way to work in a few hours!

 

If it's at all like mine you'll notice it run a little hotter at a constant cruise speed and then come down again in stop-and-go traffic. Exactly the opposite of most cooling systems on most engines.

Hope it works out for you OK, regardless.