Water pumps usually only go bad if they leak, or maybe if the shaft breaks or the impeller corrodes to chit as in no fins left(not likely).
Get the old part when you pick up your car. Ill be they say they threw it away.

 

actually he showed me the water pump he had replaced. The old one didnt seem to have anything obviously wrong with it. I could see the new one where it was put in.

I asked how he knew if it was just the thermostat vs. the pump and his logic was that if the fluid on one side of the stat was cold and the other hot, it would indicate a bad stat alone. In this case it was cold on both sides. Not sure about it all....

 

So as long as I am seeing 234-236 when sitting in traffic, that is as designed? It was about 85 and dry here yesterday and I was sitting on the freeway with the A/C on. Everything seemed to be working fine but the gauge was telling me 234 and would jump to 236 every once in a while. I get the impression that the air pushed through the radiator by vehicle motion is significantly more than the air pulled through by the fans. Also, as soon as I started moving, the temps dropped to 190 and never moved again. Cooling system just serviced. New AC Delco Dexcool at 50/50 ratio. Radiator cleaned about a month ago and checked this week. New t-stat during system service.

Just seems like an awfully big range between optimal engine temp (190) and when the cooling fans come on. It's not like they put a huge parasitic load on the engine.

Rad

 

I am having this same problem. My gauge will go from normal operating temperature to pinned (or almost pinned - sometimes pinning on 260 for minutes at a time - very scary, although the car never appears to be hot - coolant looks good, never cooks over or uses water, oil looks good) than back down to normal again just as fast as the needle can respond. I first had the problem a year ago but then it settled down and did ok for an entire year of driveing. Now it's acting up again. I have cleaned the grounds and connectors on both sides of the engine compartment and had the dealership put in a new sending unit. All to no avail.

I was wondering if replaceing the water pump and thermostat was the cure for any of the above posters.

thanks

I am worried sick it is a blown head gasket, although it shows no other signs a blown casket. If the temp is actually going as high as the gauge says it is the motor WILL have a blown head gasket and/or worse very soon. If the cyclinder temp is actually going to 260 it wont take long and apparently the temp is correct since it has a new sending unit.

again thanks for any help

 

Stop and go traffic...was it above 85 degrees?

Did you have your A/C on?

if so thats the problem...turn it off and put the windows down...uncomfortable yes...but your temp shouldn't go much about 210

 

Well over 85 degrees most days this time of year here in Memphis.

Stop and go traffic does seem to make it worse. But it will do it on the freeway as well, infrequently but it does do it, especially after some stop and go driving. It seems to climb up and then back down sometimes when i accerlate off the ramp. Other times not. I really can't find any specific circumstances that I can link for cause and effect. Sometimes just sitting breifly at a redlight idling with the temp right where it should be and then boom the needle will start jumping up and back down for no apparent reason while i'm sitting still.

I've tried it with and without A/C. (Not easy in Memphis in a black on black vette with the passenger side window inopt.) It doesn't seem to make a difference except the reduced power circuitry kicks in and out and messes with the A/C pump.

It doesn't have to go to 210 to act up. It seems to start about the time it reaches normal operating temps - when apparently the thermostat opens all the way.

There does seem to be a corrilation between the hotter it gets and the more stop and go the more the needle moves around. Sometimes if I run errands in the car it will be fine for a couple of stops and than it will start acting up. There appears to be a correlation between when the thermostat apparently completely opens and when the needle starts jumping.

I've about got myself convinced it's the pump. I had an 88 vette that lost a pump, but on that vette when the gauge temp went up the car got visibly hot pushing out coolant. In this vette (2000) when I pop the hood it appears as cool as a cucumber - or as cool as normal would be.

I did the job myself on the '88, in the back yard under the shade tree. Not all that fun. Had to pull the front of the motor off, skinned my knuckles, took the Lord's name in vain, pulled leg muscles from leaning over the car all afternoon, wond up with a small coolant leak, and a couple new swear words in my vocabulary.

 

I experienced the same symptoms as the original poster lately. I am getting a new thermostat. Extended warranty company would not approve pump replacement because there was no outward evidence of leak or malfunction.

Also having the leaky differential fixed.

I get the car back tomorrow.

 

Please let us know if the thermostat fixes the problem.

The other posters stopped posting without ever stating what the fix was. I'm assuming the stat or pump fixed it since they stopped posting after that.

 

New water pump. New thermostat. New temperature sending unit. New Dexcool. Needle still bouncing up to 260 and back down.

 

Have you looked at the temps on the DIC? Sometimes, they differ from the gauge, with the DIC temps being the one the computer uses for fan activation, etc. If the DIC temps match your gauge, you definitely have a problem, as I'm in Olive Branch and my 02 never goes above 235 F.

 

If the guage is changing like that, it most likely due to a poor/loose connection some where between the sensor and the IPC. I recommend carefully examining all the connections and wiggling each one with the ignition on/engine off (with a constant engine temp) and see if you can get it to change.

Give that a try.

BC

 

I am getting the following codes:

10-PCM
P0117 H -coolant temp sensor high voltage
P1114 H - ECT sensor circuit intermittent low voltage
p1220 H - TP Sensor 2 circuit
p1258 H C - coolant over temp- fuel disabled
p1516 H - command vs actual throttle position performance

58 - SDM (i don't know what these are)
u1000 H
u1016 H
u1096 H

80 - Radio
u1096 H

A0 LDCM (left window - driver side - operates fine)
U1255 H Serial data line malfunction
u1064 H Loss of communications with BCM
u1016 H (dont know this one)
u1096 H Loss of communications with IPC

A1- RDCM (right window has been in op. for some time)
U1255 H Serial data line malfuntion
u1064 H Loss of communication with BCM
u1016 H
u1096 H Loss of communication with IPC

B0- RFA
u1255 H serial data line malfunction
u1064 H Loss of communication with BCM
u1016 H Loss of communication with PCM
u1096 H Loss of communicatin with IPC

Watching the DIC while driveing it goes from 196 straight to "coolant over temp" back to 196 or to 241 than down to 196 or whatever the real temp is without showing any degrees in between. Or sometimes the DIC goes straight from say 192 to 224 or whatever. However, it will not start doing it till the car has been driven at around 190 (degrees not speed) for a while. If it was purely electrical than wouldn't it act up at ANY temp?

The oil pressure sending unit is pinned and that doesn't seem to be setting any codes.

 

east_river_trucker

The loss of comms issue needs to be resolved before you can really trouble shoot this issue. Theres a couple of things that you need to check:

The first and most important is your loosing serial buss data. The most common cause of this issue is a bare wire in one of the door harnesses (a very common issue). Remove the rubber accordion tubes from the passengers and drivers door:



Pull the harnesses up so that you can examine the connectors:



If you look closley,,, you will see a bare wire pulling out of the wire insulation. You need to cover and isolate any bare wires. Then see if you have the same issue.

I would also have the battery tested to see if it has enough reserve capacity to support cranking. When you crank the engine, a weak battery will allow the B+ voltage to drop as low as 8-9 VDC That can also cause a lot of those codes.

Try those things, clear ALL the codes and get back with the results.

Bill C

 

Thanks much for the help.

I did as you said and dug the wires out of both doors. I discovered the bare wires on each door as pictured, although the wires didn't seem to be touching anything. After driving the car awhile it acted up again. I turned the car off and turned the key on and wingled the door wires around. The DIC still continued to cycled thru Coolant over temp and Reduced power.

I took the door plugs apart and sprayed electrical cleaner on them (they looked fine), put them back together, put them back inside the body, took the two ground plugs under the hood apart again, cleaned them again (no sign of corrosion), pulled and cleaned the ground behind the left rear tire. pulled the battery, pulled and cleaned the ground beside the battery tray and cleaned the battery terminals (the pos side actually had some corrosion, I didn't have the right wire brush to clean it properly with but I did what i could with the cleaner and a rag, the car cranks fine), reset the computer, drove the car and again the coolant temp alarm goes on and off repeatedly and the gauge finally pins. I then pulled these two codes: (the only codes that were in the computer so apparently my other ground cleaning did do something)

10-PCM
P0117 C Engine Coolant Temp (ECT) Sensor Low Voltage
P1114 H ECT Sensor Circuit Intermittent Low Voltage

When the temp gauge pinned the DIC gave me the pornographic triple xxx for the temp reading, at which point apparently the computer bypasses the reduced power circuitry and the car runs ok - without the warning bell going on and off and the reduced power kicking in and out. Apparently the xxx sends bad data to the computer and the computer goes into some sort of default mode.

 

When you get a chance dig those connectors back out of the door jamb and wrap some electrical tape around the plug and cover the bare wire, what happens is after you tuck them back into the door jamb they can come into contact with the frame and short out, taping them up will prevent that.

Looking at the fault codes you've shown looks like you may actually have a bad coolant sensor or a bad connection (either at the sensor or the PCM), I would replace the sensor and while your there take a good look at the connector and the wiring.

 

east_river_trucker

There are TWO possible problems that you may be having. The first is bad data from the ECS to the PCM. The Eng Coolant Sensor is on the fwd drivers side of the head near #1 spark plug.

The other possibility is that you have bad serial data from the PCM to the instrument panel cluster.

We need to sort this out to figure out where the bad data is coming from. If you remove the connector from the ECS you will see a yellow wire (signal) and a brown wire (Low Ref) or basically 5 VDC. If you TURN THE IGNITION ON /ENG off then jump the yellow to the brown wire in the connector, the coolant temp gage should read a steady 280 DEG. If the gage is jumping around you know its NOT the ECS located in the block. Read the LOW REF wire to an engine ground! You should see a steady 5 VDC with zero variation. If your battery is low, it may read 4.9 but it should be steady.

If all those things check out, you could have a bad IPC or a bad connection on a board or connector in the IPC! That would be my area of primary interest. Your NOT seeing erratic engine performance so I suspect that the ECS is sending good info from the sensor to the PCM for engine performance calculations. If you have access to EFI Live or HP Tuners, you can view that data real time. If some one near you has tuning software, they should be able to examine that in a snap.

BC

 

 

I Was Having The Same Problem With My 2001, And I Cleaned The Condenser Radiator And Trans Cooler And It Made A Significant Change In My Temp, After Having The Radiator Flushed And New T Stat.

 

Thanks for the responses. I haven't had a chance to work with the car again. I can only dally with the Corvette as my scheduled work and unscheduled and scheduled debauchary allows.

I took it for a 20 mile freeway drive at 2am Saturday night The temp stayed right at a steady 192 degrees. With only minor deviations at some stop lights. Computer didn't store any codes. The outside temp was moderate, probably around 75-80 degrees.

Sunday afternoon around 5pm I took her out again. Outside temp was hot, probably 90s. Drove it about 3 mile in stop and go traffic to a Target. The temp went up to around 196. Shut the car off. Was in the store for a few minutes and than came out and started it. Temp around 201 and it started dropping as the water circulated. Drove about a mile futher in stop and go traffic to a Walmart. Came out to start the car. When I turned the key to on and paused to let the computer boot. the DIC quickly flashes "over temp" and alarm goes off. Start the car, and I get the fluctuating DIC temp up and down behaviour. More hot flashes than a cook in a kitchen. Alarm going on and off and temp flutuating the whole way back to the house. But the needle never pinned and DIC never read xxx. Again no codes in computer.

Apparently it only leaves codes when I get the xxx DIC readout, which apparently only happens if I continue to drive the car in stop and go traffic in high ambient temps.

 

I am positive the sending unit is ok. It is brand new. The plug and wire look good. But I don't have a volt meter. When I get one I will do the tests. On a cold start the temp reads fine between cold and around 196 or above, the same as the old sending unit did, which would seem to indicate that the unit is reading ok. I am only getting the problem at higher temps, which leads me to think maybe the high temps along with possibly some other configuration of data that the PCM collects is causing data to flow thru a circuit that is messing up. There could be some path of logic that the computer uses only after it warms up and collects a specific group of data that is causing the problem. But that sounds a little convoluted.


I AM seeing erratic engine performance when the reduced power circuitry activates. I assume the PCM activates that not the IPC. So possibly bad data could be going into the PCM. Or possibly the PCM could be missprocessing good data in a bad way which than triggers the reduced power to kick in and out and the IPC to show bogus numbers.

I really don't know what I am talking about. I defer to your knowledge and experience.