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Car overheating...HELP!

We recently purchased a used 99 cadillac deville.after buying it we took it to the shop for an oil change, we were told that we had a slight oil leak and slight transmission leak but that both were small snd nothing to worry about, thinking we had a decent running vehicle we took the car out of town 2 times we still didnt have any issuses until about a week later we were running errands and the car alerted us that the coolant was overheated and to idle engine…my question is what could be the cause etc?? We did buy coolant because afterwards we noticed it was low we filled it up and we r still having this problem…help advice anything???

the coolant was overheated and to idle question is what could be the cause etc??

The overheat could be simply that you were low on coolant, and that could be because you have a small leak, which might be simple to repair. Or it could be much more serious. There are a few things you can and should do yourself to sort out the symptoms.

First of all, with a COLD ENGINE, check the level of coolant in the radiator, and if it’s low, add coolant. Check the overflow reservoir as well. You’d be wise to check this daily until you resolve the problem. What you definitely want to avoid is running the engine without coolant, that could destroy your engine. You may find that you add coolant and the next day it’s low again. That could be normal as the coolant begins to refill the entire system when the engine runs. Or it could mean the coolant is escaping in assorted ways.

Are you seeing coolant on the ground under the car? If you’re not sure, start checking when the engine is fully warmed up. Do you see white smoke in the exhaust?

Just make sure not to run the car when the temp gauge climbs, and remove the radiator cap only when the engine is cold.

Take the car to a shop and have them pressure test the cooling system.
Check if there’s any obvious coolant leaks that you can see.
Make sure all the fans are working
Consider changing the thermostat and radiator cap
Make sure the accessory drive belt is in good shape, not torn up, loose or glazed

If it happened suddenly and you were not previously having problems, the water pump belt may have come off of the pulley/tensioner. The Northstar engine for your car has a separate belt for the water pump on the opposite side of the engine from the drivebelt, near the top/front.

If the belt is still on, then it could be any of the things suggested by others above, or unfortunately, it could be the head gasket. Northstar engines around this model year are notorious for head gasket/head bolt issues.

While someone may disagree with me, but in my opinion “we were told that we had a slight oil leak and slight transmission leak but that both were small snd nothing to worry about - See more at:

Tell us more about this “slight” leaks.

IMO if you can detect any leak from a transmission (Auto or Manual???) You have a problem and it needs to be addressed NOW.

When was the last time you changed your transmission fluid?  Yea a lot of people never do, but changing the fluid may save you some really big dollars by changing the fluid now.

Does ur car have temp gauge? I do most devilles are driven by elderly folks. Maybe caddy thinks temp gauges are too confusing for grand folks? When u got overheat message, did u look at temp gauge? 99 deville is statistically the worst year for headgasket issues. $3400 repair.

any time you buy a car or truck i always watch the fluids ona daily basies to make sure everything is ok

$3400 is what you might pay for a head gasket/head bolt insert repair at a dealer, but you can get it done for $2000 or less elsewhere. I’m hoping that’s not what it is though.

Let’s see. 24 hours replace head gaskets, surface and test heads. 10 hours insert install times 80 bucks an hour. That comes to just over 2700 bucks and we haven’t started in with parts yet and I work for an independent. 3400 is not unrealistic unless you’re talking about a dealer, then I would figure more like five grand.

If only we had some specifics about the symptoms…this could be no more than a bad radiator cap or a pinhole in a hose, or it could be a lot worse. Hopefully the OP will report back with some details.

Recently bought used caddy and it overheats? Never heard that scenario before. Chuckle.

Let's see. 24 hours replace head gaskets, surface and test heads. 10 hours insert install times 80 bucks an hour. That comes to just over 2700 bucks and we haven't started in with parts yet and I work for an independent. 3400 is not unrealistic unless you're talking about a dealer, then I would figure more like five grand.

Having a Cadillac with a Northstar engine, I’ve researched it quite a bit, so I’m rather confident in my answer. I’ve personally received a quote of around $1000 for just the head gasket without the inserts. If someone never did a Northstar head gasket job and was solely going by “book time”, the amount above would probably be correct.

We r thinking thinking the lower radiator hose has a leak.dont know how or why…could it be caused by not having the proper antifreeze/coolant in it?because for some unknown reason the shop put in green coolant, the car uses orange type.? Im clueless about cars excuse me if i should like an idiot.

Is there coolant on the ground?

In 14 years, the rubber in radiator hoses deteriorates, leaks are quite possible. Replacing old hoses is good preventative maintenance. If all you have is a bad hose, then you should celebrate and hope that the overheating did not do more severe damage. You may have some issues if the coolant really has been mixed as you describe.

My boyfriend looked at it and he said that yes there is coolant on the ground…another question i have is if the shop put the regular green coolant and then after i noticed it was low put in the recommended orange DEX-cool could this have caused an even greater problem??im confused about how the leak could have came about because the shop never mentoined a leak in any radiator hoses but now it seems we have one…hmm…

If you have a leaking radiator hose, then it has to be replaced. To replace it most of the coolant has to be drained, might as well finish draining the coolant and refill with either dexcool or one of the universal long life coolants. DO NOT USE the green stuff, it has abrasives in it that your system is not designed for.

If I were you, I would replace all the hoses, upper. lower and heater. Might as well get a new thermostat in there while you are at it. Do not allow anyone to flush your system, just drain both the radiator and the block. A water flush is unnecessary and a chemical flush could do further damage. With new hoses, thermostat and coolant, you should be good for 5 years of trouble free cooling.

As a caddy owner who has removed this motor before, I can discuss hoses. Where is leak? Driver side, lower area? That is where waterpump is. The WP can leak. The coolant crossover has gaskets that can leak. Very annoying job to replace those. The heater core is on pass side, firewall area. The hoses are molded and a pain to change. They usually are good but spring loaded clamps do leak. U could have a cracked surge tank. They do fail over time and cause leaks.

Topped off with coolant last night attempted to drive to the store made it about 10-15 miles and it started over heating so decided to just park let it cool n turn bk n go home…when i stopped to cool down coolant was pouring out the bottom of car passenger side…also 99 cadillac deville doesnt have coolant resevoir so u put coolant directly into radiator…if that makes sense? Correct me if im wrong here.

"coolant was pouring out the bottom of car passenger side"

OK, so you clearly do have a leak - that’s a manageable repair unless you’ve severely overheated the engine in this process. Don’t drive the car, but get it towed to whoever can find the problem and fix it. If you overheat the engine severely, you’ll end up needing a repair that’s probably more expensive than the car is worth.

If it’s just a hose, then replace ALL the cooling system hoses rather than just the failed one. If it’s the radiator causing the leak, you should replace all the hoses at the same time so that they don’t fail on you a week or month later, or at an inconvenient time or place (such as 2am in a snowstorm, or when you are late for an airplane or a wedding ;~). It’s a good idea to also replace the thermastat and radiator cap unless either are nearly new.

If you didn’t overheat the engine too severely, and if the radiator or a hose is your problem, then you should be good to go soon.