Ok...Here is my big problem just got the car..Jan..and 3 weeks ago (about) it ran hot..ok had it sent back to where I got it and the salesmen said its taken care of it was a bad thermostat..It ran good for 2 weeks after that..then today it ran hot again..Any idea what the problem could be? I figure the chances of 2 bad thermostats is extremely high..Maybe the pros can give me an insight...Also im from virginia so not sure if there is any type of protection on these types of situations..

Thanks!

 

First thing to check is the front part of the radiator (jack it up, look up toward the top, front of the radiator).

C5's are like a Hoover vacuum - they suck up a LOT of leaves, grass, plastic bags, etc. etc. etc from the road - and much of that debris ends up in the radiator area as described above.

There is a cure for this (other than not driving) - many Forum vendors sell a debris guard that takes about 10 minutes to install - and it works.

 

 

Check to make sure the cooling fans are coming on too...........

 

I vote for the radiator debris, too. Also make sure that when they changed the thermo, they got the system full of coolant. If a big bubble of air hangs around the thermostat, it might not open. Still think you'll find something caught up in the radiator, though. Post what you find.
P.S. When you say hot, how hot? In traffic, or on the highway?

 

It sounded like the fans were running but I was near a highway pulled over trying to listen to couldn't tell 100% if they were..

 

Any way I can remove that debris??

 

Yes - air compressor method works.

Also, something (not sharp!) than you can reach up there works.

 

So I take it this is a common problem for C5's?
Well its in the shop right now waiting to get looked at tomorrow..so I'll post what happened..hopefully its only what you say it was..but I don't know anything about cars so this was really helpful..
Thanks again!

 

how hot with the factory settings 225-230 not uncommon in traffic! normal

 

The needle was in the red...Hit 250 and came on and the screen told me..engine over temp or something like that..

 

Like the others said it could be trash blocking the radiator, easy to inspect from underneath the car. With it happening every once in a while it doesn't sound like a internal engine problem.
You can make sure no air is in the cooling system by following the steps in this link starting at step 11.
http://forums.corvetteforum.com/show...ain&forum_id=1

 

Is it running hot whilr idling, slow crowded traffic, or at highway speeds?

 

Ok..yesterday (Tuesday) Really nice day out..had the top out driving all around..goto work today Wednesday..running good..get home all fine...then I drive to the car wash sit in line waiting for it to get a wash and the temp gauge starts going up..then once I enter the car cleaning conveyerbelt thing the message came up saying engine is over temp (something like that)..pulled over and called the tow truck..I don't know much about cars and didn't want to push it even tho I was 5 mins from home and 10 mins from the garage to fix it..Ohh yeah and only slight steam was coming out of the side crack of the top of the hood..looking at the car it would be back left close to the windshield...

Thanks for the help!!

 

No it is not a common problem on C5s. There may be some people who have heart failure when temps reach 220 but the car is designed for that. I've had a lot of debris sucked up by my C5 but never enough to cause it to indicate an OverTemp condition while idling or driving around town or down the highway. When the OverTemp light comes on like you have indicated there is a real problem.

Assuming the thermostat is good since it was just replaced then the coolant level may be insufficient. Other worse things could be possible.

Here are some possibilities:

Engine Runs Hot, Overheats, Loss of Coolant (Polish Filler Neck/Replace Radiator Cap) #00-06-02-001 - (Jan 5, 2000)
Engine Running Hot, Overheating and/or Loss of Coolant (Polish Radiator Filler Neck and Replace Radiator Cap)
1999-2000 Passenger Cars and Trucks with Composite Radiator End Tank

Condition
Some customers may comment on one or more of the following conditions:

Engine running hot
Engine overheating, and/or
Loss of coolant/low coolant message
Cause
The radiator filler neck may have an imperfection in the sealing surface.

Correction

Important
DO NOT REPLACE THE RADIATOR.

Using a piece of 400 grit wet/dry sandpaper backed with a flat piece of wood, polish the filler neck sealing surface using a circular motion.

Replace the radiator pressure cap with a cap of the same part number as shown in the GM Service Parts Catalog.

Diagnostic Procedure for Overheating Condition

Engine Overheating
Step
Action
Yes
No

1
Inspect for a missing or damaged radiator upper or lower baffle and/or radiator air deflector.

Is the baffle and/or deflector missing or damaged?
Go to Step 8
Go to Step 2

2
Inspect for a loss of coolant.

Is there a loss of coolant?
Go to Step 3
Go to Step 4

3
Fill the system to the specified level. Refer to Loss of Coolant .

Does the engine overheat?
Go to Step 4
System OK

4
Inspect for low coolant protection.

Is the coolant to the correct concentration?
Go to Step 5
Go to Step 8

5
Inspect for a loss of cooling system pressure.

Is there a loss of system pressure?
Go to Step 8
Go to Step 6

6
Inspect for a faulty engine coolant temperature (ECT) sensor. Refer to DTC P0117 , DTC P0118 , or DTC P0125 in Engine Controls - 5.7L.

Is the sensor operating properly?
Go to Step 7
Go to Step 8

7
Inspect for a cracked coolant surge tank or a leaking hose.

Is the coolant surge tank cracked or is the hose leaking?
Go to Step 8
Go to Step 13

8
Repair or install new parts as necessary, then retest.

Does the engine overheat?
Go to Step 9
System OK

9
Inspect for incorrect drive belt tension.

Is the belt tension correct?
Go to Step 10
Go to Step 8

10
Remove the water pump. Refer to Water Pump Replacement .
Inspect for a damaged water pump driveshaft.
Is the water pump driveshaft damaged or is the seal leaking?
Go to Step 8
Go to Step 11

11
Inspect for obstructed radiator air flow or bent radiator fins.

Is the radiator air flow obstructed?
Go to Step 8
Go to Step 12

12
Inspect for blocked cooling system passages.

Are the cooling system passages blocked?
Go to Step 8
Go to Step 13

13
Inspect for inoperative cooling fans. Refer to Cooling Fan Inoperative .

Are the cooling fans and the motors operating correctly?
Go to Step 14
Go to Step 8

14
Inspect the thermostat. Refer to Thermostat Diagnosis .

Is the thermostat stuck in the closed position?
Go to Step 15
Go to Step 16

15
Replace the thermostat. Refer to Thermostat Replacement .

Does the engine overheat?
Go to Step 16
System OK

16
Inspect the radiator cooling capacity.

Is the proper sized radiator being used on the vehicle?
Go to Step 3
Go to Step 17

17
Consult the current parts catalog and replace the radiator. Refer to Radiator Replacement .

Is the repair complete?
System OK
--






Bill

 

My money is on a bad radiator cap not building pressure causing the overheating.

 

my car was doing the same thing. turned out to be a crack in one of the side reservoirs of the radiator which coolant leaked out. i first thought it was water pump or thermostat.

 

Well IM about to pick my car up. The shop told me there was air in the system. They didn't do it properly the first time when they replaced the thermostat.

Thanks Everyone for the help..now I know somethings to look for just in case it happens again..

 

Just bought a 187 deg T-stat for my 98 C5. Going to install it at the Dealer with their "Good Guy Deal" on a coolant system flush for $110.00. Going to add a bottle of Water Wetter too, anyone else use Water Wetter in their C5? I'll change the fan temp on/off with the HyperTech III after that's done. The T-stat's a one piece deal with housing & T-stat together, unlike the T-stats for earlier chevy motors. I always drilled two #30 holes, 180 deg apart, in the older T-stats and never had a prob with air. The holes let air escape and allowed you to completely fill the coolant system. I can see where trapping air could happen with the LS1 T-stat, just gotta be carefull filling the coolant system and top it off after the motor comes up to temp and cracks the T-stat by watching the coolant level drop in the plastic tank when the T-stat opens.

Glad your prob didn't hurt at all Matty K.

Mick

 

Air pocket in cooling system..after thermostat chage...just a guess