Engine overheated, may be gone. Any car experts out there?

johnniet

johnniet

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Jul 12, 1999
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My car engine suddenly overheated the other day during normal freeway driving. It's a Mazda 626, 1993.
I pulled off at the next exit and into a gas station just as the engine stopped.
(Yeah, I know, I should have pulled right over. My mistake.)
Got it towed to my usual shop. The next morning they looked at it and said it was pretty much kaput. I'd have to buy a new engine or have it rebuilt--either way, it would be well over $2000 (i.e. at least the value of the car).
I live near the shop, so I managed to drive it home slowly and carefully. It started to overheat once on the way home, and I pulled over and let it cool for a while. (They did fill it with coolant before sending me off.)

(1) Why does a seemingly health engine suddenly overheat? I had added oil a few days earlier, since the oil light came on (so there could be a slow oil leak--but it would not have run out again that quickly). That was the first time the oil light had come on in four years. The last time, I had an oil leak and got it repaired.

(2) Should I just accept their judgement that the engine is almost irreparable? They weren't very specific about what the damage was, so I have no idea where to start on this. When I went to pick it up, they charged about $45 for labor, so they can't have looked at it for that long. Might be long enough to tell though.
 
phatch said:
The oil light is a too late sign. Once it's on, it's too late.

Phil
Click to expand...

Huh. What signal should you look for instead?
The oil light came on 4 years ago too, and there was damage, but the engine ran alright for years afterward.
Why does an engine with plenty of fresh oil overheat?
 
I'm not an expert but this is what I understand to be true about what happened.

It wouldn't have been as bad if your car was still running as you entered the gas station. The fact that it stop as you entered the gas station means that the engine seized. This is probably the most damaging thing that can happen to an engine.

Overheat is a combination of insufficient lubricant (oil) and an ineffective cooling system.

Chances are, you either completely overburdened the cooling system as you lost oil, or your cooling system was not functioning as well as the oil loss.

If your engine siezed, then all the cylinders are seared and cooked. In other words, the surface of the interior of the cylinders are no longer the physical shape that they orginally were.

Its cheaper and more stable in general to buy a whole new engine and install it than to rebuild a burnt engine block.

In your case, I would just get a new used car.
 
My eyes are always flicking to the temp guage when I drive and with each car I have developed a familiarity with it's normal temperature ranges. This has saved my bacon a couple of times as I was able to notice that the car was 'running hot' and stopping before doing any damage.

The sudden overheating will invariably be a leak somewhere in the cooling system - probably a split hose, maybe a cracked radiator. If you fill the coolong system and then look under the bonnet while the car is running you should see the fluid spraying out somewhere. I would get that fixed first and see how the car runs after that before deciding on a new motor. If it is a gradual increase in the tendency to overheat then this usually means the radiator is corroding. The other explanation maybe a broken fan belt causing less cooling airflow over the radiator - but I'm sure the mechanic would have picked this up.

I have run a car to failure from overheating (hence my temp gauge watching thereafter) once and did not cook the engine, although I was lucky not to. If the engine has been cooked, thereb will be a myriad of warps and cracks internally that will be too much to fix individually.

So my advice woould be;

1) Check that the fan-belt is ok
2) Fill the cooling system while the engine is running and follow the hoses along with your hands, squeezing them strongly to see if you can spot the fluid leak. Get this fixed by either replacing the hoses or having the radiator repaired.
3) Keep using the car if it runs ok, checking the temp gauge, water and oil obsessively.
4) If the engine has been damaged it will obviously not run as well or start using excessive oil and water
 
Was the coolant in good shape?? Have you done coolant flushes every 30,000 miles?? Just wondering. That can affect it also.
$45.00 sounds like a half hour of labor. I guess it depends on the labor rate.
Will the new engine have a 3year/36,000 mile warranty??



Blades
 
johnniet said:
Huh. What signal should you look for instead?
Click to expand...

Short of an oil guage, there isn't much of a signal. Oil guages are good things, but very rare these days.

Phil
 
If you were able to drive the car home, the engine is o.k. There are a few things that can cause overheating.

Check the thermostat (or have it checked). This regulates the temperature of the engine and when it goes, the car has nothing to tell it to start cooling.

Check the radiator for cracks, leaks, etc. Is there any coolant spattered around the engine compartment? (dries white)

Check the hoses from the radiator to the engine - are they all properly connected? Any sign of leaks? (again, white residue)

The engine overheating usually has nothing to do with the engine block itself. You'd know it if you busted the block. The crank would not even turn.

Try this:

Get a friend to help. Have them turn the car on while you have the hood up watching the engine. He's there to turn it off once it gets hot. Look for any evaporating fluids, leaks, etc. See if there are any noises, smells, etc. and try to locate them the best you can.

Don't take it back to that same mechanic. Be grateful he let you drive it home without pressuring you to do something about it right then.

If the engine can run for even a minute without overheating, then it's something between the engine and the thermostat (which includes the radiator).

Does the heater work? If so, start the car up a second time and see if turning the heat on helps it stay cool longer. If that works, it's further proof what I'm guessing is right.

If the engine starts to make any funny noises like loud clicking or snapping, shut it off immediately.


Best of luck, my friend!
 
You might want to check your thermostat.

I had a Toyota truck overheat and sieze up. The guy at the shop told me that I had blown a head gasket and it was going to cost me.

I changed the thermostat, which had frozen shut, and it fixed it right up. That was at 105,000 miles. I drove it another 65,000 miles before I traded it. The guy that bought had driven it another 55,000 miles the last time I had spoken with him.

I would get a second opinion on the engine before I made any decision. You might change the oil, check for any leaks, and check the cooling system.

Yes, you might need a new engine, but you can still get one after checking out a few things first.
 
If your car is at all old, you should check the oil level regularly, especially after any fast runs, which tend to cause the oil to disappear much more quickly. If the oil light comes on, stop and turn off the engine immediately. A very low oil level can cause damage to the engine, but in my experience doesn't usually cause overheating (ie. boiling of the coolant).

Overheating can be caused by a lot of things:

Loose or broken fan belt.
Low coolant level.
Corrosion, sludge or scale in the radiator. (Do you live in a hard water area?)
Dirt, old leaves, etc. clogging the radiator matrix.
Old, collapsed or kinked hoses restricting coolant flow.
Non-functioning electric fan.
Weak fuel mixture (faulty pump; wrongly adjusted, faulty or damaged carburettors or injection system).
Binding brakes.
Jammed thermostat.
Missing fan blades.

Quite often, an older car may be developing one or more of the above problems, but runs OK. until you are sitting in a jam in hot weather or go for a fast run.

If you see the temperature guage creeping up but can't easily stop and turn off, putting the heater on full with the blower on will usually bring the temperarure down again, provided the radiator hasn't lost too much coolant through boiling. A bit uncomfortable, though.

Andrew.
 
Not enough info.

Is your water pump shot? ARe your belts in place? Is your thermostat stuck closed?

Differential diagnosis for over heat:
No/low coolant
SHot water pump
Broke belt
Low/no oil
Bad radiator
etc....

I can't think of more off the top of my head. But you need to find out what is wrong before you decide on if the price to fix is OK. Overheating is just a symptom.


Paul
 
Could be the head gasket too. I had that problem on a 626 I used to own.
 
I think koj11 is on the right track. Your symptoms indicate a blown head gasket. Check to see if there's any oil in the cooling system, or coolant in the oil, those are both good indications. If the head gasket is blown and you overheated it badly enough to cause it to temporarily seize at the gas station, it's quite possible that the had got warped or possibly cracked in the process. With both overheating and the oil light coming on I seriously doubt you're going to get off with something as simple as a new thermostat.

John
 
I just let my father-in-law who is a master mechanic read your post and he says that all signs point to a blown head gasket. You may have a chance to save your engine if you want to replace the head gasket. It will be an expensive job but not as expensive as replacing the engine or getting a new car.
 
Sudden overheating at highway speed would possibly be a thermostat , sudden lose of coolant, or possibly loss of the belt that drives the water pump.
Severe overheating most likely has resulted in engine damage. I suggest that you get a second opinion from a reputable shop and maybe a third one if you still feel unsure.

Tom
 
Its been posted already, but I'd like to add my 2c. A buddy's Toyota Rav4 overheated spontaneously while idling. Weirdest thing I've ever seen, but it turned out that Toyota screwed up in the design and put the coolant thermostat at the top of the radiator (or the top of wherever it was, may not have been the radiator) as opposed to the bottom or middle. This meant that it only took a teeny bit of evaporation or leaking of the coolant for the level to fall below the thermostat, and hence the engine management never thought the temperature was high enough to turn the fans on. Brilliant. This is most likely completely unrelated to your 626, but I'm always surprised at how little things like a few cups of coolant can so strongly affect your car.

Something to think about for future car purchases if you have deep enough pockets would be a non-water based coolant. Its called Propylene Glycol (as opposed to water-based Ethylene Glycol that everybody uses), and its drop- (ok, pour-) in compatible with everything. It has a much higher boiling point so overheating is much harder, and its much less toxic and harmful to kiddies and the environment. The downside is its significantly more expensive than regular antifreeze.

But yeah, get a second opinion; it can't really hurt.
 
FWIW, the oil light coming on is not the kiss of death. My dad's Ford Ranger would always light up when the oil was 1qt low. Add a quart and the light would go off. He drove it like this for 10 years before selling it. It still ran when he sold it.

Chris
 
just to be clear, if it turns out to be the head gasket - it was because of the overheating that it blew. Not the other way around.

The cost they gave you was most likely all labor/testing. A new gasket is ~$20.



You still there johnniet?

Can you give us a status report?
 
if the head gasket blew, then the block/head surfaces may have been damaged at that spot, or there may be warpage, and it'll need to be decked to make sure a new gasket will seal. How does it run? The head may also need to be replaced if there's a crack between the valves. Maybe that's why they say the engine is shot. A compression check is probably a real good idea.
 
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