Likely Coolant Leak Locations

[Tsar_of_Cows]

EDIT: It's a '92, not a '95. I have no idea why I thought it was a '95!

Hey all,

First Post! Woo!

I bought a 1992 DeVille 4.9L second hand from a dealer a few weeks ago and I noticed recently that the heater isn't working. Bought "As-is" with no warranty so they aren't going to fix it.

A friend of mine used to be a mechanic and he's worked on a few old caddis so we set about trying to troubleshoot it.

We checked the fuses and the blend air doors, but that was all fine, so we then checked the coolant and found it was completely empty! We filled it up with coolant and it was still blowing cold air so we thought it must be the heating core. However, between his house and mine (a 15 - 20 min drive) it ran completely out of coolant again, so I think it must be gushing coolant out of somewhere.

We didn't see anything exactly spraying coolant all over the place while we had the hood open and the engine running, and it's completely dry inside the Passanger-side Dash near the Heating core, so I'm thinking that it must be leaking somewhere else.

Are there any "usual suspects" for coolant leaks in this type of car? Places where I should check out first before anywhere else.

Also how safe is it to drive without any coolant? I mean, I've been driving it for weeks on 0 coolant by the looks of things and nothing has happened to it, but I'll stop driving it unless I really have to if I could be causing any damage.

Cheers

[navion]

If you are losing coolant and can see no outside evidence of the leak, my first inclination would be to pull the dipstick and see if the coolant was getting into the oil.

If the oil is over full and looks like congealed milk, then you have a problem. Also look at the bottom of the oil filler cap. If there is a bunch of white milky stuff there. then the engine has moisture in the crankcase.

These engines have been known to develop leaks between the intake manifold water crossover passages and the cylinder head. When this happens, the coolant goes directly into the oil. If the car has been driven very far, the rod and main bearings will most likely be toast.

If the oil looks OK, then there is a slight possibility that you didn't get the cooling system full. It probably had air trapped behind the thermostat.

Remember, NEVER remove a radiator cap with the engine HOT!

[BodybyFisher]

Likely places for the coolant to leak

Radiator end caps are plastic they crack and the seals can leak

Plastic T

Water pump

Water pump seal

The 4.9 can leak internally at the cylinder o-ring

heater pipes

heater core

thermostat seal

upper or lower radiator hose

heater core hoses

radiator cap seal or spring weak allowing the cooling system to blow off at low pressure

head gasket leak

if you are driving with NO coolant it is NOT a good thing to do you can warp your heads, I would STOP driving it immediatly and NOT drive it till you can find the leak. If you have driven this car with NO coolant you have probably ruined the engine.

Pull the oil dip stick and see if it looks like the OIL is milky

[Tsar_of_Cows]

I checked the oil level using the dipstick after filling up the coolant, it looked fine to me.

I'll check for moisture in the crankcase.

If the oil looks OK, then there is a slight possibility that you didn't get the cooling system full. It probably had air trapped behind the thermostat.

Filled it up at the radiator, ran the engine for a few seconds and then filled the coolant tank. Coolant tank went from full to empty in about 15 miles. Is it plausible that it would take that much coolant to fill up the system? (not being sarcastic, genuinely asking)

if you are driving with NO coolant it is NOT a good thing to do you can warp your heads, I would STOP driving it immediatly and NOT drive it till you can find the leak. If you have driven this car with NO coolant you have probably ruined the engine.

Yikes! I'll be leaving it at home and walking to work then. Not had any engine trouble mind.

I'll check the radiator cap before I go home today as the engine will be cold - I'll look see if there is any coolant in there or if it's bone dry, just incase it does actually have coolant in the system. I'll have to drive it home I don't want to leave it in the car park here. I haven't been driving it very far at all and it's cold here so I suspect (hope, desperately) that I haven't done any damage to it.

I'm being pragmatic about all this though, if it turns out I pissed $5000 into the wind on this car, well it was a learning experience, before I had to start working on it my understanding of it's internal workings was "It has four doors, four wheels and an engine"!

[MrEldo97]

'95...it has the Northstar in it. Check your coolant for the presence of combustion gases (kit at NAPA $50.00). If there is combustion gas in the coolant you've pulled head bolts out of the block.

[Tsar_of_Cows]

'95...it has the Northstar in it. Check your coolant for the presence of combustion gases (kit at NAPA $50.00). If there is combustion gas in the coolant you've pulled head bolts out of the block.

Thanks for the suggestion but I'm not sure if there is any coolant for there to be combustion gases in!

I'll keep it in mind though.

[MrEldo97]

You will have to refill the coolant eventually and when you do have it checked...

[BodybyFisher]

'95...it has the Northstar in it. Check your coolant for the presence of combustion gases (kit at NAPA $50.00). If there is combustion gas in the coolant you've pulled head bolts out of the block.

The 95 Deville has the 4.9 in it, not the NS

[Tsar_of_Cows]

You will have to refill the coolant eventually and when you do have it checked...

Will do.

[BodybyFisher]

You will have to refill the coolant eventually and when you do have it checked...

Will do.

The 4.9 can lose coolant in the crankcase, it is not really known for head gasket problems. I wouldn't worry about that, I would fill it with coolant and have the system pressure tested by a professional to see where its loosing coolant from. DO NOT drive the car without coolant you will SEIZE the engine.

[navion]

Filled it up at the radiator, ran the engine for a few seconds and then filled the coolant tank. Coolant tank went from full to empty in about 15 miles. Is it plausible that it would take that much coolant to fill up the system? (not being sarcastic, genuinely asking)

The short answer is YES! If the engine was extremely low on coolant just filling the radiator and the surge tank would not be anywhere near enough coolant. The fact that the surge tank emptied it's self would be a normal circumstance if there was air trapped in the engine behind the thermostat.

Check for coolant in the oil. If there is none, you may still be OK.

Did you get any overheat warnings when you drove the car? If you did, just what warning did you get? Hopefully there was enough coolant in the engine to protect the block and heads.

If you have been driving it "for weeks" with out coolant, it would have given you some sort of message that it was overheating (or just flat quit)! So I suspect that there is some coolant in the block. If nothing else, I would fill the radiator and surge tank tonight (engine cold) and wait until morning. Then in the morning check the level of the coolant and the oil. If the oil is UP, then you have DO a problem.

It will be likely that the coolant level will drop overnight as the air is displaced out of the block and heads. Top it up again. and let it sit. Eventually it will refuse to take anymore coolant.

If you fill the cooling system absolutely full, it will overflow when the engine heats up. The cap is designed to vent the excess coolant out through the overflow hose. Once it does that, if nothing else is wrong, the coolant level will stabilize and you should have heat also.

After all this, you will need to make sure that the coolant is freeze protected. If nothing else is wrong, make sure that you have a 50/50 mix of water and antifreeze. Even if you live in a warm climate, these engines need the anti freeze mixture to lubricate the water pump and protect the engine from corrosion.

[MrEldo97]

My apologies then...I thought Cadillac had completed the changeover to the Northstar by '95...

[Tsar_of_Cows]

Filled it up at the radiator, ran the engine for a few seconds and then filled the coolant tank. Coolant tank went from full to empty in about 15 miles. Is it plausible that it would take that much coolant to fill up the system? (not being sarcastic, genuinely asking)

The short answer is YES! If the engine was extremely low on coolant just filling the radiator and the surge tank would not be anywhere near enough coolant. The fact that the surge tank emptied it's self would be a normal circumstance if there was air trapped in the engine behind the thermostat.

Check for coolant in the oil. If there is none, you may still be OK.

Did you get any overheat warnings when you drove the car? If you did, just what warning did you get? Hopefully there was enough coolant in the engine to protect the block and heads.

If you have been driving it "for weeks" with out coolant, it would have given you some sort of message that it was overheating (or just flat quit)! So I suspect that there is some coolant in the block. If nothing else, I would fill the radiator and surge tank tonight (engine cold) and wait until morning. Then in the morning check the level of the coolant and the oil. If the oil is UP, then you have DO a problem.

It will be likely that the coolant level will drop overnight as the air is displaced out of the block and heads. Top it up again. and let it sit. Eventually it will refuse to take anymore coolant.

If you fill the cooling system absolutely full, it will overflow when the engine heats up. The cap is designed to vent the excess coolant out through the overflow hose. Once it does that, if nothing else is wrong, the coolant level will stabilize and you should have heat also.

After all this, you will need to make sure that the coolant is freeze protected. If nothing else is wrong, make sure that you have a 50/50 mix of water and antifreeze. Even if you live in a warm climate, these engines need the anti freeze mixture to lubricate the water pump and protect the engine from corrosion.

That's awsome news! I might be out of the woods!

And yes, I have literally been driving it for weeks, actually more like a month and a half - I bought it mid September, and, as I said, I've had no problems apart from it sometimes (i.e. rarely) taking a second turn of the ignition to start, but it always gets going on that second turn. I put this down to it being a 13 year old car and being vaguely temperamental. My ex-mechanic friend brought up two errors on the computer, error 12 and 96 IIRC, we looked them up and he described them as "normal" and as I know little about cars, I just accepted his explanation. It's never thrown any warnings on the dash.

I'll fill her up on coolant before I take her home (it's a 5 min drive home and I have two gallon tanks of coolant in the trunk) and leave it standing over night. If My garage is flooded with coolant tomorrow morning I know I have a problem!

Oh, and the Coolant I bought is 50/50 with antifreeze (friend's recommendation) - I live in Colorado, so it's getting COLD!

[JimD]

....If My garage is flooded with coolant tomorrow morning I know I have a problem!

I would say you have a solution 'cause that would mean the leak is external (hoses).

[Tsar_of_Cows]

....If My garage is flooded with coolant tomorrow morning I know I have a problem!

I would say you have a solution 'cause that would mean the leak is external (hoses).

Well that's one way of looknig at it I suppose, and at least if it's hoses it's a cheap fix I can do myself. Wow who knew I could be an optimist?

[JimD]

My glass is always half full.

[Tsar_of_Cows]

My glass is always half full.

And hopefully so's my coolant system...

[adallak]

1. Fill up the cooling system.

2. Drive a couple miles just to bring engine to operating temp and open up the thermostat.

3. Get out of the car with engine running.

4. Open the hood.

5. Increase RPM to some 4000-5000 by hand (lifting up throttle lever)

6. Watch carefully for coolant fountaining from plasticT, connections, cracks in radiator side tanks, rusted heater pipes close to waterpump, etc. you name.

[Tsar_of_Cows]

I've filled up the coolant tank again, will leave it overnight and see what happens.

I'll post again tomorrow morning.

[BodybyFisher]

Once you find the leak you must use the cooling supplement in the 4.9, do a search COOLING SUPPLEMENT. You will find a label on one of your shock towers instructing you to use it I believe

[Tsar_of_Cows]

Morning all.

Checked this morning before and after driving to work and with the engine running and there don't appear to be any coolant leaks!

However, the heating system is still blowing cold air, and I heard a noise which sounded like air escaping when it kicked in.

Any ideas?

Quick note: I got my years confused, this is a '92 DeVille 4.9L not a '95. My display pic is a picture of it.

[Ranger]

How is the coolant level now?

[Tsar_of_Cows]

How is the coolant level now?

It's full.

[navion]

Altogether, how much coolant did you have to add, total, to get it full?

You need to check the freeze point of the coolant, because you don't know if it had antifreeze or just plain water when you bought the car. Adding 50/50 mix to water will dilute the mixture and cause the freeze point to rise.

In your area you need protection to at least 30-35 degrees below zero.

If I were you, I would replace the thermostat and do a complete cooling system service after you find out why you don't have heat and get that repaired.

Perhaps others here can help with your no heat situation.

[Tsar_of_Cows]

Maybe 1.75 Gallons or so. I used 1 full gallon and most of the second.

Considering the area I'd think (hope) that it had 50/50 in before hand.

What does the thermostat control? The heating system is definitely kicking in if I set up the climate control correctly, but it's just blowing cold air at me.