Now that I have more water in the cooling system it seems to stay cooler for a while(about 1 hour) but when I shut the car off it overheats. Oil is usually around 250 and coolant 240 then you shut the car off and it overheats. I have a 160 t-stat fans come on at 130 or somewhere around there. Ac cant be used or it will over heat in about 10 minutes. Now I cant even drive the car at all. Just seems to be getting worse. When driving it seems to stay pretty cool(220-230) but as soon as I stop it just starts cranking up there. Cant drive in city traffic at all. Ac is unusable fans are working, cleaned out the rad. done most of the things people are suggesting here at the forum. Will a bigger rad. fix the problem? What do you suppose the problem is in the first place. Have underdrive pully, 160 t-stat, ARE oil pump and heads/cam pack, and many other mods that I dont think are related(zo6 intake, headers, etc...). Also have other threads going from a month or so ago but recieved no help. What would you do? Please help so I can drive my only decent car again before winter.

 

Any DTC codes set? Has P1258 been set? (over 268F)

Both cooling fans do come on at these temperatures?

Ground (102) for the fans is good? (Frame rail passenger's side engine compartment)

Have you tested the thermostat to see if it opens at the specified temperature?

Did you experience these temperatures before you had the underdrive pully?

 

Test the stat
also you may have a colapsed radiator hose... or two.. it is hard to tell visually... if it were me... I would preplace them...


[Modified by Evil-Twin, 2:07 PM 7/25/2003]fans come on at 130??????? thats way too low.. that means they are always on..... if you have a 160 stat and it tests out at 160.. fans should come on around 180 and off at 170...


[Modified by Evil-Twin, 2:10 PM 7/25/2003]

 

Yes both fans come on. I am waiting for it to cool down so I can see exactally when the fans come on(I was going from memory from last summer). Not sure how to test the tstat. I have a samco red hose kit so replacing it would suck. After ARE did my head/cam job (which included the ud pully) it ran hotter then it did before but not much. It seems to get slowly worse. I keep hearing to turn the ac on to help out. Whats up with that. If I turn on my ac it will overheat 10 times faster. Here is a list of codes. I'm going to check them out in a few, just thought I'd post them here first. I reset them and will see which ones come back, only one is current( I think)
a1rdcm
b2283h
b2285h
u1064h
------------------------------------
a6scm

b0851h
b2605h
--------------------------------------
aoldcm

b2252h
b2204h
b2282h
b2284h
b2262h
b2264h
u1064h
--------------------------------
60ipc

b0521h
u1040h
u1160h
--------------------------------------
10pcm

p0137h
p0138h
p0140h
p0141h c
p0158h
Thanks for any help!!!!

 

Have you checked to make sure your water pump is good? Your "regular" temps of 220-230 sound awfully high. On the highway I run 171° with a 160° thermo and no fan control; tops out at 205 in traffic. And your fans might be coming on too soon - 180 to come on and 170 to go off would be fine. Your car needs some time to cool the coolant, and if the coolant is constantly circulating, it may not ever be cooling down. Your thermostat may be stuck wide open also. The suggestions for turning on the A/C stem from the fact that turning on the A/C automatically turns on your fans. Generally turning on the A/C cools everything down. Something is stuck open or you've got a blockage somewhere. Have you flushed the radiator or had it serviced recently?

 

I don't think the DTC codes are related to the cooling situation:
a1rdcm: right door control module - U1064 is a communication problem with the Body Control Module (BCM), the others are battery voltage out of range

a6scm: seat control module - battery out of range and a seat position problem.

aoldcm: left door control module: door key cylinder, battery voltage, and mirror position.

60ipc: instrument panel cluster: Tach signal malfunction, The "U" DTC relate to communication problems with the electronic brake control module and the driver door module with the instrument panel cluster.

10pcm: Powertrain Control Module - These codes relate to the heated O2 sensors (HO2S) - probably related to your headers.

-------------

Did your Samco hoses have reinforcing coil springs inside the hose?

On C3s the lower radiator hose can collapse if the hose is not internally supported. When this hose collapses, coolant can't flow and the engine heats up. Some coolant hoses don't have the needed reinforcing coil springs.

I would replace the thermostat with the standard 190F one from GM. I would also replace the current hoses with standard GM hoses. Buy them at the Chevy dealer! What you want to do is return the car to a "stock" configuration in order to sort out the problem. (50/50 DexCool)

The under-drive pulley might have some effect, but the problem may just be a collapsing radiator hose, as the fans seem to be working. If it isn't the hoses, the water pump would be the next obvious player. Try the inexpensive stuff first. :)


[Modified by mapman, 5:08 PM 7/25/2003]

 

Pull it from the car and put it in a pan of water on the stove with a thermometer in it, and watch for the temp it opens at.

 

Thanks for the replys. Actually I can drive on the freeway all day and I stay at 215 give or take and 235ish on the oil. Its just when I stop the fan shuts off and the coolant starts to boil. Are the fans suppost to shut off immediatly. I pretty much had the same problem a couple years ago and putting the cooler tstat solved it. It may be a 178 I forget. The tstat staying opens sounds like it may be the culprit(who knows). It usually takes around an hour to get up to these points.

 

how do you know the fans shut off immediatly???? when you stop... they are very quiet.. also when the pcm detects a head pressure increase of 20 psi in the compressor... the fans automatically switch to high speed..... both of them and you can hear this... some one said your stat is stuck open.... they obviously dont have a clue.... if your stat was stuck in the closed position you would get no circulation.. and thats why we said check the stat,,,, buy a meat thermometer 5 dollars at the grocery store.. take out the stat ... two bolts.. put it in a pot of cold water with the thermometer... see if it opens around the 190 mark.. if not... or it only opens partially .. you have found your problem..

 

Actually I have a 178 or 172 or something like that (its been a while). I can hear when the fans come on if I am sitting in my driveway. Usually when I pull into the garage I can hear them comming to a stop just after the engine is shut off. They dont turn back on even if I turn the ignition switch, only if I start the car. Is this normal??????????

 

Make sure there are no air pockets traped in the system, there is a procedure to burp the system that the GM folks use. After that make sure you have a 50/50 mix in the system if there is too much antifreeze cooling drops. Be certian that the hoses are not colapsing this is very common with the 350 engine. Check the area between the rad. and the AC condenser for blockage. Flush the fins of both units.

 

Fans are comming on at 183(coolant). Not sure how they work, high speed, low speed wise. I think I may have herd something come on around 170 then I definitly could hear them kick on at 183. Havent taken the shroud off yet, is that what you are saying to do?

 

I just installed 1 side of headers to try it out and the header side is much hotter than the manifold side.. I would guess 300% hotter. My water and oil temp also raised... I will not drive it like it is now... I'm gonna wrap the headers first. I never knew how much hotter headers were until now... the stock side stays very cool in comparison. the header side actually heats the cooling tank up quite a bit. I'm gonna remove the header next week and wrap them if I don't sell them. I have heads and cam coming in next week so I'll wait till then to do the install all at once. Don't want to get dirty too many times. :flag

 

you can not hear the low speed fans even from under the hood.... the high speed fans are much louder.. this is what you are hearing.. they cycle off an on.. both fans have high and low speed capabilities.. when you car is cold tak a flash light and you will see the fan blades not turning.. at low speed you can not hear the fans above the engine but you will see them turning.. at high speed you can hear them .. if the air is swtiched on the low speed fans should come right on..

 

Coolant temp is way to high for the kind of driving you describe..
I suggest going back to stock thermostat and get the fan kick on temp reprogrammed to 220 or so. There are many known problems with aftermarket thermostats.
You also mentioned that you have more water in the system. Did you mod anything there??? Couldn't find any post about this.
Also, you still run 50/50 mix Dexcool/water? Dexcool raises the boiling point.

Hope this helps.

 

Scope out the basics -

1) is coolant flowing - i.e., water pump function and thermostat opening
2) if 1 is good - visually compare flow to another C5 to determine if blockage or restriction is causing overheating
3)if 1&2 are good - check with pressure gage the condition of the system and integrity of the block and head gaskets

 

What is the normal range for coolant just normal highway driving and then just sitting at an idle and then shutting down?

What about engine oil temps for the same two conditions?

 

After reading the post and your replies I have one question. What do you mean when you say it overheats when you shut off the engine? Do you mean the engine temp goes up or that the cooling system boils over? You could have several problems including a leak in cooling system pressure cap, blown head gasket, etc.
Bill

 

Fans come on at 130? Whoa, so that means they are ALWAYS on besides startup? :confused:

Also 220-230 driving is knowhere near cool, thats more like the limit you want to see. I get about 190 driving 80 mph.

 

If the fans are working as they should I would replace the thermostat, it may be defective. If you still have the problem I would suspect a plugged radiator. I have seen water pumps cause the probelm in other cars, rarely,

The fans should cycle on and off(ac off). Another indication that it may be a radiator is if it seems to run hotter when the car is working harder, pulling hills. The radiator has to displace the heat generated by the engine and if it's plugged up and not transfering the heat properly, it will run hot. :seeya