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Car overheats sometimes

J

Juand

Junior Member
I have a 2011 Impala that will wuickly overheat but when you turn off the car for 10-20 mintues and restar the vehical all goes back to normal and cars runs good again. This happens every so often. The temp needle shoots all the way up and the read out says the car is overheating. Fluid level is correct and i have no leaks. Any idea what may be the cause?
 
So it's either the sensor is wrong, or it's right.

If it's right you've probably got a stuck thermostat - I feel like a water pump would be broken all the time, not intermittently.
 
Yeah... I'm going to go with thermostat. Had that happen before. You'd better fix it before it blows your head gasket due to overheating and the pressure that is built up in the blocks coolant passages from overheating.... $5 thermostat makes for a very expensive head gasket replacement. GM made thermostat replacement fairly easy... A few bolts and a few hoses and you can replace it yourself... Just buy some fresh coolant while your at it... and depending on the motor research where the coolant bleed valve is so you can get air out of the system after refill.
 
Check the electrical connections to the fans on your radiator. This sounds a little like an intermittent problem, and a stuck thermostat normally is not intermittent. But especially if you see this problem when you're just idling for long periods or driving slow stop-and-start stuff, the fans are really necessary. If they fail for any reason the system can oerheat quickly. This normally does NOT happen when you are driving at moderate to fast speeds for sustained periods (becasue normal air flow through the rad is sufgficient even without the fans). Does that match your pattern?
 
I belive so. My wife drives the vehical so i have not had it overheat on me. The first time this happened was when she was in heavy traffic on the freeway due to an accident and just recently when she was driving in typical stop and go conditions on residential roads. I know the car has two fans and one turns on regularly while the other I'm not sure when it kicks in. Are both fans suppose to be on simultanously?
 
^ I can't state this specifically for an Impala but it is typical that only one fan comes on around your thermostat temperature then the other doesn't come on unless the temperature rises to a higher threshold, or if your A/C is on.

Both fans should definitely be on by the time it's overheating. That would be a good time to pull over and check them.

If your wife is not frail (not likely to suffer from heat exhaustion), and cannot pull over VERY soon because she's stuck in traffic, instruct her to turn off the A/C (if the system has a setting that will shut the compressor off and still...) put it on heater to lower the engine load and increase the heat shedding.

Then again, I'd go ahead and put a new thermostat on without any further thought about it since they're inexpensive, unless you have to take the intake manifold off to get to it, then it is worth looking at the fans and temp sensors closer before making that effort.
 
Good info from mindless1. So BOTH fans should come on when the engine is really warmed up AND you have the AC turned on, too. And definitely if the engine is hot. If only one comes on, it MAY be becasse the engine is not too hot yet, or it could be some failure. Like, blown fuese, bad relay, poor electrical connection, etc.

Each fan has its own electrical feed cord. If you're handy ypou can test the FAN in case its motor is faulty. Fof each fan disconnect its feed cable and try to rig a power feed directyl from the battery terminals to the fan contacts, just for a short time to verify the fan actually does start if given power.
 
I spent a lot of time and money on an older Impala that would overheat and report "low coolant" only when idling. Turn out to be warped heads. Had to bring them to a local machinist to get resurfaced. It wasn't until we noticed a discoloring of the oil (after draining all the oil) that we kinda realized coolant was mixing in with the oil. Seriously, long story short...lol

Full disclosure, it was my wife's mechanic family that did most of the work on it. I just helped.
 
I have one of those Bluetooth Readers, too. FYI, it's a little module you plug into the ODB2 port of your car (almost all have them under the dashboard right by the driver's left knee).It draws electrical power from that port. All it does is read the codes from your car's little computer system, then communicate these using the Bluetooth wireless system to an app on your smart phone. I got the full version of Torque - you pay a modest price and download from Google app store. The app can show you those codes, but basically in numeric form. BUT if your phone has internate access (I do it by our house WiFi) it gets the actual brief meanings of each code to show you. It also allows you to set up screens of readings of MANY values of engine and accessory performance data in real time as you drive, like speed, RPM, temperartures, gas flow, etc., etc. I had it use the phone's GPS feature to trace out my path on a Google Map as I drove to a store and back. You can specify several auto profiles for the cars you use it on - I have mine set up for four vehicles. And of course you can clear the old codes off once you have diagnosed things. Works very well! Total cost for the reader and software under $40, compared to MUCH more for a dedicated ODB2 reader tool from an auto parts shop.
 
I was going to post a separate thread to solicit second opinions, but this one seems about right.

I'm sprucing up my old 95 Trooper and our 95 Nissan truck this year. I'm currently waiting until next week to take it back to the repair shop; a mechanic there damaged connections in my wiring harness, and I'm holding their feet to the fire for returning the car with operational horn and windshield wiper/washer.

The problem with the wiring harness arose because the same mechanic broke my heater core in process of replacing valve cover gaskets. He replaced the heater core and was careless with the dashboard and wiring harness.

None of this is the fault of the Trooper, nor is it my fault, other than authorizing a valve cover gasket replacement which might have waited another year or two.

NOW is our hot season in So-Cal, and I'm running the AC a lot. All fine with that, but I've begun to notice that the radiator overflow reservoir fills up too much after running the car, parking it and letting it cool off. And when I remove the radiator cap, there is an air pocket at the top of the radiator.

I'm not losing radiator fluid, except when it spits out the top of the reservoir.

The oil is clean, without any contamination from the cooling system. No emulsified stuff seen when peering through the oil filler hole in the valve cover, so no indication there of a blown headgasket.

The coolant is pure and clean as can be expected; there's no oil emulsion in it that would suggest a blown head gasket.

Nothing is coming from the exhaust except a little pure water while the car is warming up, and regular exhaust gases -- again -- no indication of a blown head gasket.

I replaced the radiator cap, but this situation persists. Next week, I'm going to replace the thermostat, once I received my parts in the mail from RockAuto.

When I fill the radiator back to the brim and allow the car to warm up before replacing the cap, I may notice the fluid jump a little bit here and there, but it isn't gas bubbles. It appears more consistent with a thermostat opening/closing erratically. The prevailing wisdom suggests that a head gasket leak causing exhaust gas to enter the cooling system would show "profuse bubbling" at the radiator top, and this isn't happening.

So you can comment at will about these remarks. But here is my main question.

The Trooper OE thermostat is rated at 170F. The factory shop manual spec "valve opening temperature" is 166F to 173F. I ordered two thermostats and gaskets: a 170 and a 180.

Should I try the 180F thermostat? And if I do, would I only expect that idle engine temperatures will only increase slightly so the temperature needle on the dash will peg a tiny bit higher? Or should I stick with the OE-spec 170F thermostat?

Update: Still interested in comment or second-opinion answers. However, it looks as though my symptom was caused by overflow hose deterioration at the radiator cap. The cooling radiator will suck as much air from such a leak as fluid it can draw from the reservoir. Will soon know for sure . . .

So . . . 170F or 180F thermostat?
 
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I'd stick with the 170. I live in Northwestern Ontario, a little north of Duluth MN. So in deep winter we get a lot of cold. In this area it WAS a common habit (not so common now) to switch to a thermostat with a higher temp rating for the WINTER cold season. This was to ensure that the engine got all the way warmed up before the coolant flow through the radiator started cooling it, AND the heater had a good chance to deliver more heat to the interior becasue the coolant temp was higher than in summer. In your case in So-Cal you have the opposite concerns. You want to ensure that the engine does NOT overheat and gets good cooling at all times, so it is better to have the thermostat open at a lower temp.

What you describe makes sense. It puzzled me that the cooled-off rad had a big air bubble in top. I was thinking that should only happen if the surge tank ran right dry as the engine cooled off, but surely you would notice that. An air leak in that connecting hose explains it.

I just will note my observations with an open rad cap as the system warms up when you refill it. The refill process always leaves some air in the engine which gets to escape after the engine warms up and the thermostat opens, of course. So when that happens there's a surge of flow and big bubbles, and then the rad fluid level drops. Often that's when you start topping up, and a few more smaller bubbles may be released. But separate from that, what I find as the thermostat goes though its open and close sequence and the rad fans turn on and off in resonse to temperature, the fluid level in the top of the rad rises as the system warms, then drops as it cools. This really is expansion of the coolant fluid as its temperature changes. Depends on your system, but sometimes I find it useful to squeeze the rad hose slowly during this time in case it has any air bubbles trapped. Once it's stable, I top up the rad to just filled and slightly overflowing into the surge tank, then put on the cap and make sure the tank level is up to the "Max" line since the system is at max temprature.
 
Paperdoc said:
I'd stick with the 170. I live in Northwestern Ontario, a little north of Duluth MN. So in deep winter we get a lot of cold. In this area it WAS a common habit (not so common now) to switch to a thermostat with a higher temp rating for the WINTER cold season. This was to ensure that the engine got all the way warmed up before the coolant flow through the radiator started cooling it, AND the heater had a good chance to deliver more heat to the interior becasue the coolant temp was higher than in summer. In your case in So-Cal you have the opposite concerns. You want to ensure that the engine does NOT overheat and gets good cooling at all times, so it is better to have the thermostat open at a lower temp.

What you describe makes sense. It puzzled me that the cooled-off rad had a big air bubble in top. I was thinking that should only happen if the surge tank ran right dry as the engine cooled off, but surely you would notice that. An air leak in that connecting hose explains it.

I just will note my observations with an open rad cap as the system warms up when you refill it. The refill process always leaves some air in the engine which gets to escape after the engine warms up and the thermostat opens, of course. So when that happens there's a surge of flow and big bubbles, and then the rad fluid level drops. Often that's when you start topping up, and a few more smaller bubbles may be released. But separate from that, what I find as the thermostat goes though its open and close sequence and the rad fans turn on and off in resonse to temperature, the fluid level in the top of the rad rises as the system warms, then drops as it cools. This really is expansion of the coolant fluid as its temperature changes. Depends on your system, but sometimes I find it useful to squeeze the rad hose slowly during this time in case it has any air bubbles trapped. Once it's stable, I top up the rad to just filled and slightly overflowing into the surge tank, then put on the cap and make sure the tank level is up to the "Max" line since the system is at max temprature.
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The plot thickens! It is still true that the rubber-hose from radiator cap to overflow tank was leaky, but it wasn't the major cause of the air-bubble at top of the radiator.

After owning some ten vehicles, using different repair shops and doing many repairs myself, I can say that I've finally encountered The Mechanic From Hell.

Not only did he break off one of the pipes for the heater core with removal and replacement of the intake-manifold during the valve-cover-gasket renewal, but he left a leak in a small hose connection between the intake-manifold throttle body and the main engine cooling jacket as it flows to the top of the radiator. Someone told me that I wouldn't notice any "bubbles" while the car is warming up and radiator cap removed, if the leak was on the input side of the radiator -- the upper of the two main hoses.

The small hose connection as I described it has about 1/4" ID and is about 4" long, with a hose clamp at either end. The upper clamp at the intake manifold was a generic screw-adjustable clamp of the type anyone can mentally visualize. It hadn't even been tightened! It was loose enough to whirl around or even slip off the hose from its proper position.

The coolant flows from the intake manifold into the main outflow pipe to the upper radiator. I don't know for sure if another air bubble would accumulate in the intake-manifold cooling jacket. There was no evidence of it, or you would think the air would all be pushed to the top of the radiator.

I'm inclined to post a new thread with the story of the sequential cluster-f*** caused by the Mechanic from Hell. I'll entitle it "Little Shop of Horrors: The Mechanic From Hell".

Carelessness? Or maliciousness? Neither motivation would make a positive contribution to the shop-owner's business. Lately, when thinking of the Mechanic from Hell, thoughts of the old movie "Treasure of the Sierra Madre" come to mind.

I can imagine the Mechanic from Hell leaning over my old Trooper, muttering. "Troopers?! We don' need no stinkeen Troopers! Whadda we need any stinkeen Troopers for?!"

But I . . . . need . . . my stinkeen Trooper . . . .
 
M<y speculation is simple carelssness, not malcious acts. Anyway, I really hope this discovery does solve you issue. Thanks for the update.
 
Paperdoc said:
M<y speculation is simple carelssness, not malcious acts. Anyway, I really hope this discovery does solve you issue. Thanks for the update.
Click to expand...
Serial carelessness with more than one screw-up in a single step!

It really needs a separate thread: "Little Shop of Horrors: The Mechanic from Hell". It has "Aww, you don' need that old Isuzu" written all over it. But I'm also inclined to be paranoid. . . .
 
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