Cooling Problem, help ?

[Gerald]

Drove car yesterday, got VERY hot almost to the poing of overheating and I was like "huh??". Luckily there was a garage near, pulled in and expexted to see radiator hose off, leaking or something of that matter or belt slipping or broken.

None of the above. I looked in the tank under the hood (resevoir or overflow, I always forget) and it was EMPTY. How'd that happen? I'm not leaking anywhere, no coolant in the oil, no dripping, nothing. I mean, I was waaay down on coolant, put a gallon in. After I put coolant in, car ran cooler than it EVER did. NExt day, started to get hot again, and needed more coolant.

I'm perplexed. Could it have been a huuuuge bubble finally burped? any ideas? Car is running a ---little---- warmer than usual, probably 5-10 degrees past the center tick. strange..

Gerald

 

[Ulysses]

Do you still get what looks to be condensation AFTER the car is warmed up? Have you checked for coolant in your oil, or oil in your coolant?

 

[BruceW]

Might not hurt to check your spark plugs too

 

[Ulysses]

And a compression check if the plugs look fouled.

 

[Don Hiltz]

I recently experienced the same problem and was perplexed too. Interestingly, however, when my intake was removed because of a leak in the fuel rail the viper tech noted that there was a leak around the thermostat housing. It was not obvious because the coolant dried before it became visible.

My extended warranty paid for the new unit as well as the labor involved in the R&R.

According to STAR, this is a fairly common problem.

Good luck............

Don

 

[Tom F&L GoR]

Same was happening to me; turned out to be the radiator cap. It would let fluid out upon heating, but loss of suction wouldn't pull fluid back in. And because the Viper coolant system is the way it is, it would refill the tank on the fender every trip, hot coolant inside the engine would boil, push the cooled fluid out of the tank into the overflow, but the bad cap wouldn't **** it back in. Several trips later, you've pumped a lot fluid out, got nothing back. If you can't find anything wrong, get another cap.

I posted the part number for a spring center cap; don't have it in front of me. This was about 2-3 weeks ago, try using "Stant" and "cap."

 

[XS TORQ]

I had a cracked thermostat housing that caused me to leak coolant. Hopefully nothing more serious than a radiator cap....

 

[GR8_ASP]

An empty overflow bottle (the one in the fascia) is indicative of a leak somewhere in the engine cooling system. Some areas are hard to see, but I would bet that there are signs of leakage. As indicated above places to look are the water pump, thermostat housing, and other obvious coolant locations. Beyond that internal leakage (to the combustion chamber) can also be present with no clear symptoms. Pulling the plugs and looking for cleaner than normal plugs, borescoping to see washed pistons, or even smelling the exhaust for the good old sweet glycol aroma.

On the other hand if the overflow bottle is full then a leak in the purge circuit (radiator cap or hoses between the hot bottle and the overflow bottle), or a combustion leak in the head gasket is probably at fault. The purge circuit works under vacuum so needs to be leak free. You will not see any coolant leak as it leaks air into the system.

So the status of the overflow bottle is key here. Hope that it is that the latter as the head gasket is not a pleasant story.

The condition that you first mentioned is called morning sickness. That is the temperature rises to a pretty high level and then suddenly drops below thermostat opening temp. That happens when an air bubble is present and prevents the thermostat from opening, because it is not in contact with the coolant. Once the thermostat has direct coolant contact it opens quickly (sometimes because of a turn or bump causing the bubble to move). Then cool water enters the engine and the thermostat closes again . The cycle does not tend to continue until the next shutdown when the air can accumulate again. Sometimes running the heater during the warm up period can prevent this as then water is flowing through the heater circuit, helping evacuate any air bubble that may be present.

Good Luck!

 

[Gerald]

Thanks for the replies.. OK, check the overflow in the fascia and it's completely full. I have one of those radiator caps that releive pressure. Perhaps that went bad and it's allowing air into the system.?


G

 

[GR8_ASP]

Sounds like either the cap or the return hoses. Cap is most probable. Much better issue than the head gasket (course that is still possible if it is excess air entering the system, beyond the purge capability).

 

[95Viper]

Gerald, I had the same problem too. Make sure your get one of the newer spring center caps, like on a 2001. Call Tator and you'll have it in two days. It has a black plastic top. Do not get one like a 95 with a metal top and a drop center.

Also, there is a tube from your surrogate tank (with the radiator cap) to the facia tank. The tube changes from metal to rubber about 3 times. Clamp those connections with a little spring clamp kit from Autozone for about $2. It has been known that they push fluid out but draw air in when cooling.

 

[94yellow]

Had the same problem changed to a new cap and clamped hose to facia bottle at cap, no more problems. Get the cap for the 2001, they look the same but the spring is the key.

 

[Tom F&L GoR]

Part number help:

http://vca2.viperclub.org/forums/showflat.php?Cat=&Board=UBB14&Number=454314&Forum=All_Forums&Words=Tom%20radiator%20cap&Match=And&Searchpage=0&Limit=25&Old=3months&Main=453931&Search=true#Post454314

 

[Gerald]

OK, Took car to the garage. Think it's the cap. The put car under pressure for about 3 hours at 16 lbs and NOT a drop came out anywhere. They were perplexed. The only thing not used was the cap I have because the pump they used replaces the cap. Gotta be the cap......


G

 

[GR8_ASP]

Plus remember the failure mode you are describing is in the vacuum mode and not the pressure mode.

 

[King RT10]

Maybe the block and reservior were both near empty (water) and when it got hot again it pulled the water from reservior a second time (after you refilled it) leaving the reservior empty but filling the block.

 

[95Viper]

Gerald, they don't understand the system. Putting it under pressure doesn't do anything. Ron is correct above. It's the cooling down period when your problem occurs and under vacumn.

Do the cap and clamps and your problem will be gone. I hope you didn't pay much for them to mess around for 3 hours.

 

[Gerald]

Plus remember the failure mode you are describing is in the vacuum mode and not the pressure mode.

whaaaa? now I'm confused.

 

[99 R/T 10]

G,
just make sure your overflow is up to the prescribed level and have a good cap. I believe the rule of thumb is that for every pound the cap can hold pressure, it raises the boiling point up 3 degrees. Hence, over heating is is going to be some where in the 250-260 range, but we don't like to see our cars get past the 200 range(at least not me).

Mike

 

[95Viper]

Gerald, During heating, pressure forces the spring center up and fluid pushes out the tube on the side of the radiator cap into the facia tank. Your facia tank level goes up a little when hot. During cooling, vacumn does the reverse and pulls fluid out of the facia tank. Your problem could be two-fold. 1. The rubber to metal connections on the hose could be drawing in outside air, thus leaving some fluid in facia tank and allowing air in system. 2. A failed or spring type cap gets stuck and pulls air in. Easy fix.

 

[Tom F&L GoR]

Sorry to oversimplify, it's just that this is how it happened to me. When you **** on a straw and stick your tongue on it, the liquid stays in the straw. That's what you want the line between the radiator cap and reservoir in the fascia to do. If you remove your tonque, the liquid falls back in the glass. That's what a poor seal (cap, hoses, hose-to-steel line) will do. OK, so it that so bad?

While fluid is pushed to the overflow bottle in the fascia and doesn't get back sucked in, the real problem is the pressurized tank doesn't simply **** in air, either. It keeps getting refilled because it's not the highest part of the system. Somewhere inside the engine, an air bubble keeps getting bigger and bigger. Then suddenly you run hot... and you know the rest of the story.

 

[GR8_ASP]

This has been stated several times but I will try to simplify it.

When your engine heats up the coolant expands. When it has expanded such that the coolant pressure is at the radiator cap pressure (usually stated on the cap). Further expansion causes coolant flow from the cooling system into the overflow bottle (the one in the fascia). That is what causes the coolant level in the fascia to rise to the hot line. [Note for the Viper consider the fender mounted bottle to be a part of the radiator]

Now when you turn off your engine and the coolant cools it starts to contract. As it contracts it quickly lowers in pressure from the radiator cap pressure (say 15 psi) down to zero. Further contraction causes the cooling system to dip below atmospheric pressure and thus creates a vacuum in the cooling system (note the quantity of coolant in the engine at this point is less than it had when it was initially cold - some is now in the overflow reservoir). The vacuum starts to draw back in fluid from the reservoir to replenish the system. Now if there is a leak anywhere in the system it will draw in air instead of coolant, as the air provides less resistance than the coolant that is being raised from the overflow bottle. So, if an air leak is present in the overflow circuit it will allow air to enter the system during the cooling period. This will repeat every hot/cold cycle adding more air and removing more coolant until some sypmtoms start to appear such as overheating, morning sickness (described above), or visible coolant coming from the overflow bottle.

Now the question about how the air leak can occur. It can occur if the radiator cap seal leaks when under a vacuum at the radiator cap seal. It can occur anywhere in the overflow circuit. Note the overflow circuit never receives any pressure so the only leakage that will ever be noticed will be during the vacuum cycle. The other possibility is if the radiator cap purge valve (the center valve) is stuck closed and prevents the vacuum from pulling coolant through it. When this happens you will may see hoses collapsing during the cool down period, and probably collapsed when sitting cold. Air will aspirate into the system from somewhere in this case as well, as the vacuum can reach very high levels if the cap has no flow from the overflow bottle. Note that full pressure caps are much more prone to this failure mode than partial pressure caps. Full pressure caps have the center valve sprung to the closed position. These caps also create a higher vacuum in normal use as the vacuum is what opens the center valve. As such full pressure caps are more prone to this type of condition, even if the cap is perfect.

Now why did the pressure test not catch this. First it removes the cap. So if the problem is the cap it cannot find it. Dealers do have a separate test for the cap itself which can properly test both pressure and vacuum modes (if they use it of course). However, unless a separate test is performed on the overflow circuit (presumable a vacuum or decay type test), an air leak in that circuit will go unnoticed. Good mechanics will observe the full overflow bottle and look for possible leaks though.

Hope this helps. I tried to explain this in plain speak to the best of my ******** ability.