A coworker of mine has a 1996 Ford Aspire 1.3L with a weird overheating problem. I have a guess of what's wrong, but I won't say yet as I want to see if others here come to the same conclusion.
The symptoms are that it only overheats on the freeway, but not at idle and slow speeds. It has a fairly new radiator, thermostat and water pump. The faster the engine runs, the more it overheats. And it overheats a lot and fast when on the freeway at speed on level ground
Let's hear some guesses before I say what I think the problem is.
-Don-
Last edited by DonTom; 01-22-2009 at 05:03 AM.
Coolant movement by convection is sometimes enough to keep the temp down when at idle. So I'm focusing on things that would prohibit the flow of coolant when the engine has a lot of demand placed on it.
- Thermostat stuck closed
- Blocked coolant passage(s) in the head or block
- Bad water pump
Chip H.
Assuming the radiator/water pump and thermostat are in good shape and working properly, the first thing that comes to my mind is a head gasket problem. That would account for the overheating under anything more than very light loading - again, assuming the major cooling system components are all ok, based on what you've stated. (I'm guessing the cooling fans/shrouding are working and intact because the car does not overheat at low speeds.)Originally Posted by DonTom
It could also be the timing is way advanced somehow ....
When I was a Fiat mechanic, we had a customer with an Audi 5000 with those exact symptoms. Turns out the thermostat was stuck OPEN. When you force water through the cooling system with too much velocity, it doesn't have time for the radiator to cool it.
I don't buy that, but I have heard that theory before. IMAO, the speed of the water being too fast will cool just as well. The only job of the thermostat is to set the minimum temperature. An open thermostat does the same job as no thermostat and has no affect on anything other than the engine might stay too cold when it's cold.
Let's hear some other opinions on this. My guess is you had a partially opened themostat that provided enough cooling for idle but not enough for freeway speeds.
I have ran many older cars without a thermostat and never had an overheating problem because of it.
However, these days an open thermostat can cause the MPG to drop because it will make the car run cooler and therefore richer.
Besides that, the thermostat has already been replaced with a new one (to no avail) in the 1996 Ford Aspire.
-Don-
Last edited by DonTom; 01-20-2009 at 12:03 AM.
"the first thing that comes to my mind is a head gasket problem."
Yes, that was my guess too! That's what I told him, I just wanted to be sure that my guess was a good one.
BTW, I did tell him to check the upper radiator hose temperature when very hot. If cool, it means the water is not circulating well, such as a stuck closed thermostat. But if extra extra hot, it most likely means the head gasket.
-Don-
Yep - especially on this engine, which if I remember right has an iron block and alloy head.
Has he looked into the radiator (engine cold)? If the gasket is failing, you'll often see either greasy-looking coolant or bubbles (start the engine - cold - with the cap off and watch the coolant).
Yes, he mentioned bubbles in the coolant while running. That was the only other symptom he could find other than the high RPM overheating.
-Don- San Francisco
Bubbles in coolant... bad news. The head gasket is definitely bad. The problem is going t get worse - probably sooner rather than later. If he wants to save the car, I'd advise him to get it fixed pronto - before the overheating warps the head beyond fixing.
If it is an iron block with an alloy head I would recommend getting the head skimmed before refitting it as a matter of course if it more than around 3 thou warped. It can save in the long run.
Ken.
Die dulci fruimini!
Ken.
Wolds Bikers, Lincolnshire, England.
Silly question, but has the cooling system been bled properly? I'm not familiar with the Aspire, but I know that some cars require careful bleeding to get all the air out of the system.
If it needs engine work the cost is liable to exceed the value of a '96 Aspire.
Oh I got it backwards, the Audi was overheating at idle and fine on the highway.
Much more common. Often that's an electric fan not coming on, but many other things can cause that too.
Not if he does the work himself. Head gaskets are not that expensive. And a little 4 cylinder shouldn't be that big of a job.
-Don- Reno
I never heard of that! Seems to me that would get fixed in no time just by normal driving.
-Don- (Reno)
When the cooling system is drained, there are sometimes air pockets (in the engine especially). This is why it's a good idea to "burp" the system to purge any air that might be in there. I run the engine (from cold) with the radiator cap off - to warm-up. If there are any major air pockets in there, they'll be purged this way - since the system isn't pressurized yet (until you reinstall the radiator cap). Be careful not to rev the engine, though - or allow it to get too hot/overheat while idling.
Yeah, after draining and refilling. I do that too, or else it takes longer to fill the radiator because there's air taking up space and you have to keep on adding more right after each time it's filled.
-Don- (in rainy Reno, NV)
With some cars it is necessary to follow a set bleeding procedure to get all the air out. Worst I had was my Peugeot 405. To bleed that three bleed screws, one on the top of the radiator, one on the thermostat housing, one on the return from the heater, had to be opened & the system filled until liquid came out of each bleed screw. Then the engine had to be run with the radiator cap off until the thermostat opened - the big 'burp' signalled that all the air was out.
I recall reading that the older E-class Mercedes had to have the back of the car lifted in order to "burp" the cooling system. Why the back, I don't know -- it seems counter intuitive.
Chip H.
A bad air block in the cooling system will never work its way out by itself.
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