First, do a pressure test............you can rent one free at AutoZone or O'Reillys. You may have a bad coolant cap.

Have you bled the system properly?

 

That's what it sounds like the cooling has not been bleed. Plus with a 16 year old coolant cap, might be good to replace it. Also would un hooking and re hooking the battery help reset anything???

 

Didn't do a pressure test or try a new cap yet. I did bleed the system and let the air bubbles out.

 

Bleeding is a good first step. If its boiling out the cap, that's a sure sign of a failed coolant cap. The fan turn on temps are high enough that the coolant will boil before the fans turn on if the cap goes bad and won't hold pressure.

 

thanks man... thats going to be the first thing that i pick up tomorrow. if i find out that i have been dealing with this for 4-5 months now, and replacing things that didn't even need to be replaced, i am going to be pissed over a $10 cap. lol

 

If the car is over heating, IE getting TOO hot, it isn't the cap. All that does is keep the system pressurized to raise the temp at which the coolant boils...

You need to get your fans programed to come on at a lower temp...

I had this problem in my first 94 9C1 and did exactly what you have done.. replaced everything.. turned out that if the AC system is NOT charged, the fans won't kick on.. BUT if you turn your AC on, (working or not) it will turn on 1 fan (iirc its the secondary)

If you unplug the coolant temp sensor on the water pump, it throws a code, and does what you said, dumps fuel, turns on both fans, and takes for ever to start...

So make sure your AC system is charged, AND have your fan temps set to kick on at a lower temp... In the mean time, drive around with your AC turned on it'll keep one fan on..

You can also do the fan switch mod.. which allows you to turn on the fan manually, it doesn't affect their normal function, (ie with the switch off, they still kick on automatically)
hth
Jonathan

 

If the car is over heating, IE getting TOO hot, it isn't the cap.

A bad cap can definitely lead to the car overheating.

 

You can also do the fan switch mod.. which allows you to turn on the fan manually, it doesn't affect their normal function, (ie with the switch off, they still kick on automatically)
hth
Jonathan[/QUOTE]

How does this fan modification work, because I've been seeing a lot of this on the forum as of late? And what all is needed to be purchased to do the mod?

 

You can also turn on your MAX A/C which will kick on one of the fans.

This sounds very similar to the issue I had a few months back. I ended up having a bad cap and my thermostat was stuck just barely open. Like you said I would do fine on the highway and driving around town but sitting in a parking or stuck in traffic and I would watch the thing climb!

After doing some research I found that the fans kick on only at EXTREMELY hot temps (to hot in my opinion and will reprogram them to kick on at least 10 to 20 degrees cooler) I believe the temp is 222 and 232 degrees (too lazy to look but it's up there)

I ended up replacing the hoses in mine as well as the parts you described as well as the "T" fitting between the overflow and heater hoses as well as this little plastic restrictor. Both of those items were pretty gunked up too. Since I replaced all of this my car has never made it past 1/2 heat even on 2 hour road trips.

Like the previous posts said I would start looking at the cap and making sure you have a good bleed. Parking the front on a good incline helps A LOT.

Good luck, let us know if the cap worked!

 

A stuck thermostat will cause it to over heat, but it shouldn't cool down at highway speeds with a stuck thermostat, that should cause it to overheat all the time. (unless maybe the LT1 dual spring stat will cause something funky? either way, replace it)

Please explain why a bad cap would CAUSE overheating? It would cause coolant to boil at a lower temp, but not cause the temp to go up (unless you somehow boiled all the coolant out, but that is a different story)
A bad cap shouldn't cause an increase in engine coolant temperature.. Please correct me...

 

Please explain why a bad cap would CAUSE overheating?

Water boils at 212 degrees. For every pound of pressure you put water under, it will raise the boiling point approximately 2 degrees. So a good 15 pound radiator cap will raise the water's boiling point 30 degrees from 212 to 242 degrees Fahrenheit. Add 50% of coolant and the boiling point of the mixture is well over 265 degrees


steam can't be pumped by the water pump, that's why the coolant needs to stay in a liquid form. So if the coolant turns to steam too early because of a bad radiator cap or a weak mix of coolant and water, the car will overheat at lower temps, which explains when you are in an extended stop in traffic on a hot summer day.

Also, even if your not pumping steam through the waterpump you will quickly trap air in your cooling system which can cause your car to overheat.

THAT BEING SAID...

It would cause coolant to boil at a lower temp, but not cause the temp to go up (unless you somehow boiled all the coolant out, but that is a different story)
A bad cap shouldn't cause an increase in engine coolant temperature.. Please correct me...

I totally agree with this as well. While a bad cap isn't necessarily contributing to the heat problem. It def isn't helping. Keeping the coolant system under pressure just helps keep the car from overheating.

If he has never replaced the cap it's probably a good idea to and to clean off the crud around the cap on the overflow tank.

 

as far as the cooling fan switch mod, there are several ways to do it, I don't recall exactly how to do it as it has been years since I did mine..

One way is to hook the switch to the wires coming out of the power box in the engine bay, pass side rear. and go directly to the ground, (PCM completes the circut by grounding the fans)
the other way is to do the same, but install a relay so there is no code thrown..
Again I can't give you specifics because it's been years since I did this mod...
Jonathan

 

Thanks, As stated, by both of us, a bad cap, or no cap won't CAUSE the high temp. When the high temp is reached, if it is not under pressure the coolant will boil at a lower temp.

Unless he is running straight water (which is a bad idea as well, but that's a different story) His engine should not cause temps high enough to boil the coolant out of the water pump even at standard good old fashioned atmospheric pressure.

If this boiling out problem is occurring, you have more to worry about than just the cap.
in my 10+ years of owning over 10 Bbodys, only twice have I seen the my temp gauge go above the lower half of the range... Once, on my first 94 9C1 when I was having problems similar to the ones stated by the OP with inop. fans, and I told of how I remedied these problems. The second time was in my current 95 9C1 when I had a bad radiator...

But those were OVER heating, ie getting too HOT.. Nothing to do with boiling coolant.

"Now here is the issue. When the car gets hot, OBVIOUSLY the fans are supposed to turn on. At least the Primary one first. It doesn't. The car just over heats. Now, if i am driving the car and NOT just sitting at idol, the car is cool because of wind hitting the radiator, and i also have the heat running all the time."

His problem is the cooling fans don't come on.
Not sure WTF that has to do with the overflow cap?!? Again Please explain..
BTW I did very well in physics, over 10 years ago when I took it. The problem is this is applied physics
Jonathan

 

Did you happen to check those big fuses in the fuse box that powers both fans?

 

yea... i replaced the fuses and the relay's... today i just did the cap, no luck... fans wouldn't turn on. I didn't let it get to boiling point where it overflowed though. I just turned it off knowing it would get there.

 

The problem is the car is overheating. The fans wont kick on until the temp gauge is at 3/4. He already stated the fans come on when the sensor on the water pump is removed so the fans are working. Therefore its probably not the cap, not the fans...

 

You are correct sir.
The fan temps need to be lowered in the PCM. Also your AC system needs to be charged... Don't ask me why, or the physics behind it, but for some reason they'll kick on when the AC is charged and you won't over heat.
Jonathan

 

Weird... You can't even blow your nose without re tuning the PCM in this cars.

 

If everything is working correctly you do NOT need to screw with the PCM. I live in Phoenix & run a 180* stat, never have an overheat problem...does it get up past 1/2 way on the gauge in city traffic...yes, my primary kicks in at the first mark above 1/2 , shuts off at the 1/2 way mark. When my pri. fan motor died it would get the to mark just before the red before the sec. fan would kick in....still didn't overheat/boilover. Not a 50/50 mix of antifreeze = boilover, bad cap = boilover, no fans while siiting still = boilover. That's just the way it works in these cars. The PCM stuff is when you install a 160 stat...THEN program the fans to come on a little bit earlier. Really , any other advice is pretty much rednecking B.S. IMHO. Unless someone lives in a hotter place, and can justify why they did what they did.

 

So your saying your fans kick on at half way on gauge? can you hear when fans are kicking on? its weird that i cant hear my fans come on but ive done the test to see if fans are good relays are good and took sensor off water pump while car is running and fans turned right on. Reason i ask this is because u say ur fans comin on at half, and it seems my gauge when driving thru city for awhile and lots of idling it gets to 3/4 alot, but idk if thats normal or not

 

So does a bad cap cause car to heat up more than normal? i cant really tell if my fans are turning on cant really hear them, also when my temp gauge gets a lil paste 3/4 right before the line the temp gauge needle then goes right to the middle or i little before the middle, maybe fans turning on, Today i noticed when my car has been running for a while and i parked after driving for about an hour on city streets i noticed coolant dripping from driver side of bumper. I then opened hood and saw coolant tank not over flowing but it did have some coolant leakeage cant really tell where but its not a lot. So im thinking is there hoses under bumper? cant be then im thinking is radiator bad? possible but this leak i saw today dont happen often just after long city driving. Lastly could it be a pressure thing? I dont know any advice on this?

 

Also im thinking maybe i need bleed the coolant, idk if air bubbles can cause overheating or high temps, but its a thought.

 

If you see the gauge drop, and your not running down the road for any length of time and you see the temp drop, then yes, that is your primary fan kicking on, it kicks in around the 3/4 mark, can't be exact as the gauges are not perfectly accurate, then it will shutoff around the 1/2 way point...also keep in mind that the engine driven WP does not flow full until 1800-2000 rpms, I found this out when my pri. fan was out. , Keeping the revs up around that RPM helped to keep things cooler. If you let it sit in your driveway with the hood open you should will see then fans kick in & out, you will probably never see the sec. fan run if everything is working correctly...I haven't except when my primary fan was shot. Putting a manual fan switch in can also hamper the cooling if you keep them on during 35+ mph running, you don't need a fan at this speed, or any speed above that, a running fan will actually slowdown the air passing thru the radiator, thus causing you to run hotter.

Alot of air in the system will cause an issue, I believe that smaller one will work their out way after a few heat & cool down cycles. You can always park somewhere with the front angled up and lossen the bleeder vavle a little and see what happens, you might get a little air out if the system has been opened up for any reason in recent past, otherwise I doubt you will get much.

 

Then why am i getting some coolant leak on driver side under bumper? its not alot and it only happned twice so far, where is this coolant coming from? is it radiator drain plug loose or something?

 

Drain plug would be the first place I'd check also, and if its leaking you can be it sucking air.

 

What I am trying to figure out here is, why my primary fan is not coming on. The car is not over heating because of a cracked head, or a leak somewhere. The car is over heating because the fans do not come on. Primary or Secondary.

I just replaced the cap today... it did the same thing. Once it got to 3/4 i knew it was just going to over heat and bubble out as usual, so i just shut her down before that happened.

I let it cool off for an hour or so, and just unplugged my water pump sensor. by doing this, it took a little longer to start, but both of my fans came on and stay on the entire time. This is fine, but the reason why it is doing so, is because the computer thinks my car is 2 million degrees, and dumps more fuel into it. So now on top of a gas leak that i cant seem to find, i have this. Sunoko is going to love me until i figure this out haha.

I am just at a loss for words... I may just run a switch and manually do the fans. I have now replaced, thermostat, both fuses, both relays, cap, water pump sensor and fans are still not coming on..

HERE IS A QUESTION:

How many water pump sensors are there? 1 or 2? I know and replaced the one, to the bottom right hand portion of the water pump. but is there another one somewhere?

 

Does the pri. fan run with the A/C on?

 

Gregg, Why let it boil over and get really hot when you don't need to? I live in upstate NY and as previously stated have seen my temp get needlessly hot, so when getting pcm work done, had the fan temps turned on sooner... cheap insurance... You don't have to run a cooler Tstat to have the fan temps kick on sooner. If it is even close to boiling, you are WELL above 180* and the stock Tstat is already open. How is that rednecking anything??

 

oops I was replying to Gregg-o's last reply on Page 2

As he pointed out, you don't want to run the fans constantly, just when sitting in traffic when the temp rises...
Also as stated, don't unplug the coolant temp sensor. Fuel mileage sucks, and it takes for ever to start.. Just turn on AC, and check to see if the secondary fan kicks on.. It should..

OP: You never answered my question.. Is your AC charged and blowing cold?

Also there are two coolant temp sensors. One on the water pump. This is the one that matters, and goes to the PCM

The second one is on the side of the engine IIRC it is on the pass side, but I could be mistaken... This just goes to the instrument cluster.. IF your engine is over heating and coolant comes to a boil, then the gauge is probably working

 

Did u change the pig tail when u replaced the temp sensor? Did u recently put in a 160 stat without reprogramming?
I put a 160 stat in my car without reprog it and the fans would not turn on at all.

 

With the leak on the driver side bumper. Could be as stated a drain plug. I'd also check the bypass line from the coolant housing to the throttle body as well as the line under the throttle body going toward the rear passenger (the rubber portion). Also get a good good look at the radiator to make sure it isn't busted anywhere...

The fans should come on right a 3/4 to the red. At least mine does as this may be normal for our cars.