I went down to the caddy dealer and got a heater core hose and came home and put it on,after taking the car for a ride I got the "engine coolant hot" message again and then it went off and diddn't come back on. I puller over and check after a little while and noticed upon checking my coolant tank that it was empty! I went into the trunk and added the rest of the coolant I had and it was almost full.

Then after I got it home about 5 miles or so and checked again the coolant tank was empty again! What could be causing this? my mother has a buick lasabre that did the same thing and after taking it to our mechanic we found out the water pump was going bad could the same thing be happening to my deville? Ranger If not the water pump what else would casue engine coolant to leak out this fast? For those who may not know my caddy is a 1994 sedan deville with the 4.9 liter engine.

If the water pump is not turning, it will overheat and boil out of the overflow. Check the belt tensioner. How about the radiator cap? Does it hold 15 or 16 psi? You may have to have that checked at an auto prats store or shop. Are you adding coolant to the radiator or the overflow tank? If you are adding to the overflow, there may be air still in the system and it will overheat. The radiator MUST be full to the cap. Are you running the proper 50/50 mix? How about the thermostat? Have you checked or replaced it? Has the cooling system been maintaned? Could the radiator be half clogged?

Ranger the belt tetioner is fine to my knowledge and I could open the radiator as it was to hot. I added coolant to the overflow tank(this is the tank that holds the coolant right?). Also I'am using the proper 50/50 mixture and where is the thermostat and how do I check if its bad or not? If the car was overheating woulden't I get the warnings on my display,and could there be coolant in the radiator going through the cooling system even if theres none in the coolant tank keeping the engine cool?

As for the cooling system being maintained I had the coolant flushed and coolant suppliment tablets added back in april of this year right after buying the car. Last thing is if there was air in the system how would I get it out of the system? Please forgive all the questions I don't know much about cars thanks ranger for the help so far.

Hmm, I don't like where this is going. Yes, the over flow tank is the tank that holds (excess) coolant. When it is cool, open the radiator cap and be sure it is FULL. That should get most air out of the system. If there is a small amount left, it will purge itself after you shut down.

The thermostat is at the engine end of the upper radiator hose I believe (haven't had a 4.9 in several years). The only way to test it is to remove it and place it in a pot of water with a thermometer and watch to see what tempurature it begins to open.

If all that checks out then you probably need to have the cooling system pressure tested and/or the cylinders pressure tested.

Ok I'll do that first thing tomorow hopefully it will remedy the problem,it sounds like from what your telling me ranger that air in my cooling system may be my culprit then? You also said you diddn't like where this was going and you mentioned a coolant system/cylinder pressure check please elaborate ranger do you think I have a serious problem on my hands here?

ranger is right the thermostat is at the driver side of the engine follow the upper hose it will take you right to it . fill the coolant in the car run it in the driveway and watch to see if it is leaking by the water pump ,while your in the area see if all the water pump bolts are tightend, it will leak fast if one is loose. once the car heats up you should see where its leaking from

Rnager I just checked my radiator and it dosen't have coolant that I can see even shinning my flashlight down in there. Roquesr I will check the water pump tomorow and see if I can see it leaking from there. I've heard that if I try to shake the water pump and it dosen't move that its not loose is this right?

Well, if you are getting air in the system, then the next question would be where is it coming from, assuming you did not mess with the cooling system. Worst case scenario is a head gasket gone bad and allowing exhaust gasses to pressurize the cooling system. That would push the coolant out the overflow thus causing an overheat situation.

Pressurizing a cold cooling system with a hand pump will tell if it will hold pressure and likely show where the leak is. If you do this, you want to remove all the plugs so if there is a bad head gasket and the coolant leaks into the cylinder, you will see a spray when the engine is cranked. Also you will not hydrolock the engine. This test can fool you though if the leak is small and will hold under 15 psi (cooling system pressures). The positive test is to pressurize each cylinder one by one with shop air to 120 psi for :15 or :20 min. and watch for bubbles in the radiator neck (cap off). A quick check of this would be to start the engine (cold) with the cap off and watch for air bubbles, but be prepared to put the cap on in a hurry as it will overflow very quickly once it warms up and the thermostat opens. You probably has a few minutes to watch it before it happens.

couple questions

what does the exaust look like ? any smoke ?

that waterpump can be streaming coolant out of its pee port ....in which case the pump is bad

are we leaving coolant on the ground ? top the coolant off and run the car in the driveway watching the engine as it runs and the coolant level , when you start dropping the level start looking under it around it and behind it to find any drips , make sure to keep the A/C off to ensure you dont mix up AC condensation for coolant.

how does the oil look ? hopefully it doesnt look like chocolate milk ...

check the heater tee back there , when i had the one heater hose go i lost my heater tee 3 days later ...so check that tee thats back on the firewall just above the rear valvecover

Typiclly the 4.9 doesnt loose its headgaskets , but i have heard of them leaking at the intake manifold and i have also heard corrosion causeing the block to actually fail in spots , similar to a old fender rusting out , ive seen one of these block failures , its really strange to know how thin the block really is around those cyalnders , normally these failures are pretty spatacular , you would know fore sure where the leak was...its cuased by poor matinenace

check the radiator where the plastc part meets the metal (end tanks), my radiator blew out right there 3 weeks ago ,so i had everything in the cooling system replaced at that time , i really dont want any more issues LOL

Stoneage I left a little coolant on my garage floor it looks like it came from where the water pump is. As for the tail pipe theres no smoke or anything coming out of it,and the oil looks and smells like oil. I really hope to god its not a bad head gasket or the head gasket leaking at the intake manifold. How much would it be to fix either of these issues? Ranger to answer your question I haven't messed with the cooling system at all except having it serviced this past april.

As stoney said, 4.9's are not known for head gasket problems. I would run it til it starts leaking then find the leak. If that doesn't work have the cooling system pressure tested and that should help find the leak if it is external and from what you say, it is.

Ok thanks you guys I'll do that tomorow an report back here with what I find.

I have a 91 Deville and found that I found that the coolant tank would be empty. I too wondered where it was going. :confused:

I found a crack in the bottom of the tank and the water was leaking out in drips. :banghead: Not enough to really notice a lot of water on the driveway.

Countilaw