On my 95 vette the temps will get to about 220-230 before the fans come on. I can turn on my a/c and at about 200 and my primary fan will run. Have you tried running the a/c to see if the fan will run? Unless you are driving the temps will be hot. I had a 91 vette that the secondary fan would not run at all and I put a bypass w/ a switch so that I could made them run when ever.

 

fans dont come on until 228F

You did burp the system?

 

Do you have the FSM? you need to trouble shoot it-of course you've
checked fuse-right? disconnect the electrical connection on the temp switch-turn the key on-ground the wire-if the fan comes on now-you
have a bad thermo switch.If the fan does not come on check the relay,
on my 87 it's in front of the master cylinder on the wheel well-jump terminal A (black/red wire) to terminal E (red wire) if the fan comes on now-replace the relay. Fan should come on even if the system needs burping.

 

The fuse checked out ok.. I will check the relay as well. I turned on the AC as well and the fan didnt come on. All I get is cool air coming out. If I turn on the heat.. the same thing. Cool air. Doesnt seem to be coming out with enough pressure.

 

Well I ran the car for a few mins trying to b urp the system by holding it at 2000 rpm with the radiator cap off. It only dropped a little but not enough for me to pour more coolant in. SO I let her run to 230.. and the fan still didnt come on. I then turned off the motor forgetting to put the cap back on and coolant poured out! Jeez. As for the relay... I think i remember replacing it last summer. The one that sits in front of the MC on the wheel well.

 

I'm not familiar with your 87 but you should have at least 1 bleed screw (poss. 2) on your cooling system. Did you open it (them) when filling / burping? If not, you may still have trapped air in the system.

 

Not sure if I know what you are referring to.

 

On my 92, I have 2 bleed screws. 1 on the T housing and 1 under the TB drivers side. they must be opened when refilling to allow the trapped air to escape. I would 'guess' you would have at least 1 on yours. If so, maybe some one with your engine will jump in here to advise where.

 

Unfortunately, the 87 has none. They were added in later years. They would make things easier.

 

Boiling and spouting after shut off is perfectly normal. I'm sure you weren't expecting it, but there is no reason to be alarmed. If you have two fans, you have two fan relays. Again, if you have an auxiliary fan, it is controlled by a thermal switch in the left head (1987) between the #1 and #3 spark plugs. With the ignition "On" pull the wire off that switch and ground it. If everything is OK, the fan will run. You can check your FSM, but that fan may not be triggered until the water passes 235°.

L98s have no cooling system air bleeds. That is the province of the Gen II, reverse flow, cooling systems.

RACE ON!!!

 

I think I only have one fan... I will check the thermal switch today.. as for the air in the system.. how do I get the air out without pulling the waterneck again ?

 

Pulling the water neck again will only get you back to where you were and will gain you nothing. The problem with the C4s is that unlike most cars, where you add water isn't the high point in the cooling system, therefore air gets trapped in the high point. Typically, "burping" the cooling system is the solution. With the cooling system as full as you can get it, with the engine running, warm with the stat open, heater on, and the cap off, rev the engine to about 2000 rpms. You will see the coolant level drop with the rpms. While the engine is still revving, top off the radiator and reinstall the rad cap. Make sure the cap is on before lowering the revs. It is now full or very close to it. Once it cools to where you can remove the cap again, it may still take a little more water. I usually check mine 2 or three times after I've refilled the system. It doesn't hurt to have the front end jacked up or on ramps through this procedure.

RACE ON!!!

 

I'll try that trick today. I will see if I can get a buddy of mine over here to rev the engine while I watch and pour more coolant in it.

 

Well it was the relay after all ! I replaced it and sure enough the fan came on at about 233-234 F . However the heater was blowing hot air for awhile then later the air became cool. Then the engine shut down itself. Did that two times after letting her run idle for awhile. Is this normal ? Doesnt look like it to me.

 

The heater blowing hot, and then cold is typical of a cooling system that has air in it. Your engine shutting off is unrelated. Now you have something new to fix. Start by pulling codes.

RACE ON!!!

 

That was what I thought. Waiting for her to cool down and will get back out there again.

 

When you do the burp procedure that CFI-EFI mentioned, make sure that the overflow tank has fluid in it to the HOT level. Also, like he said, ensure that the heater is turned on. Otherwise, the system doesn't fully fill throughout and when the engine starts to cool it will pull air from the overflow tank instead of coolant. That puts you right back where you started.

Your 87 L-98 is an extremely close match to my 88 L-98. According to the 88 Factory Shop Manual, the main fan should come on at 226*F or 108*C. The main fan is also activated when the ECM registers 240psi at the A/C Coolant Fan Switch, even if the coolant temp is well below 226*F as long as ambient temp is above 60*F.

The senor used for the digidash temp reading and the one used by the ECM to register coolant temp are different, so when the fan turns on a slight difference from the expected reading is ok, but it should be pretty close. Mine is always within 1~2 degrees. If you are seeing a larger discrepency, you might consider testing both sensors for accuracy. The ECM cannot turn on the fan at the correct temp if the sensor is off.

 

Ok I wasn't aware the coolant overflow tank needed to be filled to HOT so it doesnt draw in air. I will do that as well. Also my fan has been coming on at 234 - 235 F right now. Has been coming on evertime and drops the temps to 211. I supposed its working properly.

 

The ecm won't see the temperature if there's no coolant there at the intake base. The temp you see on the dash is from a lower sensor that does have coolant on it. Burp that system again, and top the overflow off.

The first time you run the car to max temperature, especially after shutting it off, it'll push out some air and coolant out and suck in some more coolant when it cools. Some will overflow onto the ground, not a problem.

If your overflow ever goes dry, you have air in the system.