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1993 Plymouth Sundance
2.2L with TBI
36K miles

My temp gauge seems to constantly fluctuate from below the 1/3 mark to slightly over the 3/4 while driving. It will sometime sweep the distance back and forth, sometimes it will stay at the 1/3 mark, and then heat up to 3/4 mark at stop signs. I have tried almost everything to solve this problem, with no success.

1. antifreeze flushed and replaced.
2. tried 4 different thermostats, including 180 degree
3. tried drilling 1/8 pin hole in thermostat housing
4. tried 'burping' coolant several times
5. new radiator and hoses
6. replaced head gasket (head was apparently warped) milled and checked for cracks

The problem persists. The mechanic doesn't know what to try next. He says it's not the gauge, since he ran it on the scanner. He said the 1/3 mark is approximately 190 degrees and 3/4 mark is approx. 217 degrees. The fan turns on at 217 degrees, according to him. I know this type of fluctuation can happen in colder temperatures, but the fluctuation on this Sundance happens in any and all temperatures. Heater works fine. I first noticed the wild fluctuations going through the Rocky Mountains, going down long declines (not the inclines!) with engine rpm winding up from gravity, the gauge would sweep radically back and forth. The problem persists, and I am concerned about warping the head again.

Running out of ideas and money. Can anyone help, please?

 

[dana44]

And no indication there is a problem with the overflow allowing fluid to move back and forth and remain constant so as not to have air sucked into the engine? What about the radiator cap itself? A weak cap can do this, as the engine warms up, if the pressure isn't maintained and it can allow the temp to rise and swing like this. At this point, out of safety for the head gasket fear, you could get an electric water temp gauge with actual numbers on it to see if indeed it is heating up to the point of boiling over point. Not sure what the expected running temp is, I know one of the other guys does, but I would figure right around 205degrees, If it's burped good, lack of pressure is the only thing it could be.

 

[adsjds]

And no indication there is a problem with the overflow allowing fluid to move back and forth and remain constant so as not to have air sucked into the engine? What about the radiator cap itself?

The entire radiator was replaced...cap and all. There doesn't seem to be any issue with overflow tank.




A weak cap can do this, as the engine warms up, if the pressure isn't maintained and it can allow the temp to rise and swing like this. At this point, out of safety for the head gasket fear, you could get an electric water temp gauge with actual numbers on it to see if indeed it is heating up to the point of boiling over point. Not sure what the expected running temp is, I know one of the other guys does, but I would figure right around 205degrees, If it's burped good, lack of pressure is the only thing it could be.

Which raises a good question...what is the normal temperature fluctuation of this engine supposed to be? And at what temp does an aluminum head actually warp?

 

[Bob Lincoln]

Probably still some trapped air. It can take awhile to burp these engines. Is the coolant level holding steady in both the radiator and the overflow jug?

 

[dana44]

OK, so the cap is new, but can you check it so ensure it is holding the necessary pressure?

It isn't so much the temperature the engine runs up to that warps the heads, but a matter of how much squish is done to the head gasket first, then the leaking afterwards, meaning the head gasket is made thinner from the heat expanding the head to the block and then cooling down, the head gasket being compressed and starting off pushing the cylinder exploded fuel/air out the gap, increasing it over a short period of time and causing an imbalance of temperature to make it warp (along with head bolts stretching due to the heat, basically becoming loose given the now compressed head gasket thickness.

Even though the temp gauge is working, it may simply be more sensitive than it should be. There are resistors to keep them from swinging too quickly, and at the same time I have seen small drop sized weights added to prevent the gauges from swinging too quickly. A second gauge can be picked up for less than $20 to make verification of the gauge swings too far, not the engine overheating.

 

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Bod said: Probably still some trapped air. It can take awhile to burp these engines. Is the coolant level holding steady in both the radiator and the overflow jug?

It seemed to be eating a little out of the overflow (which is why I had the head gasket done) but I wasn't driving it consistently enough to be 100% sure. Turns out the gasket was fine, although the machine shop said the head was warped .006 at the center.

OK, so the cap is new, but can you check it so ensure it is holding the necessary pressure?

It isn't so much the temperature the engine runs up to that warps the heads, but a matter of how much squish is done to the head gasket first, then the leaking afterwards, meaning the head gasket is made thinner from the heat expanding the head to the block and then cooling down, the head gasket being compressed and starting off pushing the cylinder exploded fuel/air out the gap, increasing it over a short period of time and causing an imbalance of temperature to make it warp (along with head bolts stretching due to the heat, basically becoming loose given the now compressed head gasket thickness.

Even though the temp gauge is working, it may simply be more sensitive than it should be. There are resistors to keep them from swinging too quickly, and at the same time I have seen small drop sized weights added to prevent the gauges from swinging too quickly. A second gauge can be picked up for less than $20 to make verification of the gauge swings too far, not the engine overheating.

But that is the question: how far is too far? If someone could tell me what the average/normal temperature swing of a 2.2 dodge engine was, that would be very helpful.

 

[dana44]

That I don't know, but figured someone else would chime in on that, carbed, TB'd and injection engines all run at different optimal temps.

Air pockets are notorious for collecting in the rocker pedistals of the 2.2 and 2.5 heads, a nice steep hill once the engine is warmed up, and some good revving and idling, revving and idling, for about 10 minutes has worked for others.

.006 is not that much of a warp actually, head bolts will overcome this, as your head gasket was still good.

 

[valiant67]

You need to get a coolant system pressure tester and test the cap and the system. You may have a small leak somewhere slowing it to suck new air into the system.

 

[chuzz]

Check your hose clamps. I had that problem on my 94 Spirit and it wound up being a slightly loose hose clamp on a heater hose. It was sucking air in through that little spot.

 

[Bob Lincoln]

Normal temperature swing in a moderate climate is between the 1/3 and 1/2 mark in these engines, with occasional excursions near the 2/3 mark in very hot weather or conditions. These changes are slow (greater than 15-20 seconds typically), so anything faster than that indicates a problem - air bubble, loss of coolant, air ingestion, stuck thermostat, failing head gasket, radiator cap, pump, etc.

 

[adsjds]

Normal temperature swing in a moderate climate is between the 1/3 and 1/2 mark in these engines, with occasional excursions near the 2/3 mark in very hot weather or conditions. These changes are slow (greater than 15-20 seconds typically), so anything faster than that indicates a problem - air bubble, loss of coolant, air ingestion, stuck thermostat, failing head gasket, radiator cap, pump, etc.

Thanks Bob....what would be helpful to know is what that 1/3 to 1/2 fluctuation amounts to in actual degrees. My gauge seems to climb up to slightly above the 2/3 mark in about 20-30 seconds at stop lights or sometimes just going down the road, and then will drop back down slightly faster. However, when I was in the Rocky Mountains, I noticed a much faster cycling between these increments....not on the incline, mind you...but on steep declines with the motor revving at higher rpm's. Non of this seems to be affected by ambient temps. I behaves exactly the same way in 30 degree weather as it does in 90 degree weather. Since this problem seemed to begin at the high altitude of the Rockies, could this have something to do with barometric pressure? The car was purchased in Phoenix and now resides in Minneapolis.

 

[Bob Lincoln]

Barometric pressure is not a concern with fuel-injected cars, which have a MAP sensor to adjust for altitude changes that might affect air/fuel mixture.

Does this car have an automatic transmission? If the transmission runs hotter (such as during engine braking, or climbing hills), that heat will be transferred to the radiator via the cooling lines.

 

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a

Does this car have an automatic transmission? If the transmission runs hotter (such as during engine braking, or climbing hills), that heat will be transferred to the radiator via the cooling lines.

Yes, automatic. But the temp generally rises at stoplights and idle, when the tranny is not under load. Also, there have been instances where i could get the temp to drop at idle by revving the engine. I realize that doesn't make sense given the car's behavior in the mountain declines at high rpm's, and the fact that it will also rise when driving highway speeds, but there doesn't seem to be any logic to this problem (hence the frustration and gobs of money spent). I don't think there is a flow restriction problem, because I cracked open the t-stat ounce with the motor running and got blasted in the face. Could it just be that my gauge is too sensitive and sweeping too far? Again, there is no way to tell without knowing the normal fluctuation in actual degrees.

 

[valiant67]

When my old Dakota had a weak hose clamp and it sucked air and the temp would climb (especially at idle) then drop down after it spiked up. I found out by revving the engine that the temp would usually drop quicker. I suspect the reason was because the faster spinning water pump moved the coolant faster and created a bit more vacuum to seal the leaking hose connection just a bit rather than sucking air. I finally put a pressure gauge on it after a week or so of this and found the weak hose clamp on the lower radiator hose. Fixed that and the gauge never spiked again and temps stayed close to normal at all times.

Buy, borrow or rent a coolant system pressure tester and see what happens. Your symptoms sound exactly like a car that is ingesting air into the coolant system.

 

[Bob Lincoln]

a

Yes, automatic. But the temp generally rises at stoplights and idle, when the tranny is not under load.

It IS under load when idling in Drive. There is more slippage, and that generates heat. That's why you should put it in Neutral if idling more than a minute.

 

[dana44]

20-30 seconds at idle making the temp gauge move is way too fast, the thermostat should regulate that a little bit better, engine warms up a few degrees and the thermostat would compensate for that slight change. It really sounds like air in the system still, which, as we all know the air being heated in a small pocket will raise the temp faster because it displaces the fluid. Hill parking with the front up higher, revving a few times, watching the temp gauge, after checking all the hose connections for looseness is the last thing I could think to do. If the thermostat was sticking the temp wouldn't fall so quickly, or would drop down below the normal operating temp most likely because chances are it would stick both ways, opening and closing, I guess the only thing you haven't done is replace the water pump itself?

 

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20-30 seconds at idle making the temp gauge move is way too fast, the thermostat should regulate that a little bit better, engine warms up a few degrees and the thermostat would compensate for that slight change. It really sounds like air in the system still, which, as we all know the air being heated in a small pocket will raise the temp faster because it displaces the fluid. Hill parking with the front up higher, revving a few times, watching the temp gauge, after checking all the hose connections for looseness is the last thing I could think to do. If the thermostat was sticking the temp wouldn't fall so quickly, or would drop down below the normal operating temp most likely because chances are it would stick both ways, opening and closing, I guess the only thing you haven't done is replace the water pump itself?

Right....i haven't replaced the water pump because of the low mileage and because the flow seem more than adequate when I cracked the t-stat open. I will try the steep hill method, although I have tried putting the car on ramps with the cap off, to burp the system. The steel plug in the water box on the head is totally seized.

 

[dana44]

Yeah, that plug seizes almost all the time. Hey, don't feel bad about not being able to figure this out any more than us. Several years now, there have been overheating 2.2/2.5 engines with a bubble of air in the system that was messed with for weeks and even months before all the sudden the problem was gone. From past discussions, the pillars the rocker arm pivot points sit on are like upside down ice cream cones and collect air bubbles. It takes the angling upwards so the hose out the engine and thermostat is the highest, the front of the motor higher than the rear (gives a natural direction air bubbles will move from back to forward towards the radiator, and a whole bunch of really good revs over as much as 30 minutes time to get them out. You could find a dozen or more topics on this being a problem, so don't feel bad.

 

[Bob Lincoln]

I tried to remove that bleed screw 1 week after I bought a new car. No go. They never come out.

 

[Doug D]

Yep. I have had 3 2.5L's and the bleed screw was corroded shut and impossible to remove or loosen. The t-stat housing is the "high" point of the cooling system and any air has a tendency to get trapped in the housing.

As mentioned parking the vehicle on and incline or ramps should be enough to allow it to burp. So long as all the clamps are tight and no air can enter the system this should work.

One trick I've used is to drill a 1/16 hole in the flange (flat area) of the t-stat and install with the hole at the 12 o'clock position. This will allow any trapped air to exit to the radiator and burp out, but doesn't allow too much coolant to flow to affect the proper operation.