[valiant67]

I've said it before, but if you've got a bleed hole in the thermostat already and this keeps happening you are probably getting NEW air into the system. You've got to find and fix that.

 

[adsjds]

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.

Yep...my t-stat has that 1/16 hole drilled in. No help.

I've said it before, but if you've got a bleed hole in the thermostat already and this keeps happening you are probably getting NEW air into the system. You've got to find and fix that.

But wouldn't that spot leak as well? I've been over every inch of this engine and firewall....there are no leaks and the hoses and the radiator have been replaced. I guess a pressure test wouldn't hurt. Thanks.

 

[valiant67]

But wouldn't that spot leak as well? I've been over every inch of this engine and firewall....there are no leaks and the hoses and the radiator have been replaced. I guess a pressure test wouldn't hurt. Thanks.

I have had a leak that sucked air but never put a drop of coolant on the ground. it can happen.

 

[Bob Lincoln]

I had a very slightly loose hose clamp at the water pump-suction hose connection. I was losing a handful of coolant a day, but maybe only one day a week was there anything on the ground, and even then, only a few drops.

 

[adsjds]

I have had a leak that sucked air but never put a drop of coolant on the ground. it can happen.

Do you recall where your air ingestion was happening?

I had a very slightly loose hose clamp at the water pump-suction hose connection. I was losing a handful of coolant a day, but maybe only one day a week was there anything on the ground, and even then, only a few drops.

I re-used the factory tension clamps for all of the new hoses....do you think it would be better to replace them all with regular hose clamps?

 

[Bob Lincoln]

Yes, I always discard those. They don't let you tighten them up, and they often rust and break in half while in place, making you think they are still working.

 

[valiant67]

In my case, it was a 5.9 V8 in a truck and the problem was the lower hose on the water pump.

 

[adsjds]

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.

Well, I installed a mechanical water temp gauge and it looks like the factory gauge is totally inaccurate and inconsistent. At idle, the new gauge followed the temp up to 195 degree, and registered the thermostat opening. Let a sit a while longer and it reached up to 215 degrees, and then the fan turned on, bringing the temp back down to 190 degrees.

NOW the problem seems to be that my Sundance is too cold going down the highway!!! I made the mistake of switching t-stats at the same time I did the new gauge sensor install. NOW It wants to hang around 160 degrees going down the road, instead of 190 degrees. This is a brand new factory 195 degree t-stat with 1/16th hole. Anyone have any ideas? I am getting so exasperated with this car.

 

[chuzz]

Where did you get the thermostat? And PLEASE tell me it wasn't Autozone.

 

[dana44]

Agree. That means the thermostat is opening properly, but not closing.^^^^^^ Please don't say Autozone. The 16th inch hole is not going to allow that much overcooling, given the temp did rise to 215 and open and extra cool properly at idle.

 

[Bob Lincoln]

I just replaced my radiator on my 93 Daytona. It looked fine, fins looked great. It was losing maybe 4 oz of coolant a day and nothing on the ground. The coolant jug was not replenishing the radiator, telling me I had an air leak. I found by looking closely that there were pinhead-sized drops on the block. That told me I had a pinhole in the radiator, so small I could not find it. I changed the radiator, it burped for two straight days, while replenishing from the jug. It's been stable for a week now. Burping took about a quart from the jug, total. Temperature doesn't go over the 1/3 mark, and on the highway is between warm and 1/3. It had had occasional excursions to the halfway mark.

You can't go wrong with a Stant SuperStat. Superior damping technology, warms up faster than ever before.

 

[adsjds]

Where did you get the thermostat? And PLEASE tell me it wasn't Autozone.

Agree. That means the thermostat is opening properly, but not closing.^^^^^^ Please don't say Autozone. The 16th inch hole is not going to allow that much overcooling, given the temp did rise to 215 and open and extra cool properly at idle.

No, I bought a factory dodge t-stat from the dealer...and drilled the 1/16th hole. The heating and cooling cycle seem exactly as it should be at idle, but when I went for a test drive a couple hours later (from cold) the engine took forever to heat up, and didn't actually get up to temp until after about 10 miles of driving.

It seemed to average around 170 - 180 degrees (hitting some 165's/160's), although it did get up in the 190- 200's during some city driving. It actually had a Stant super-stat in previously, but that is when it got hotter than it ever had before (at least according the faulty, oversensitive factory gauge). I should have replaced one thing at a time. I wonder if they sold me a 180 degree dodge t-stat, if there even is such a thing?

 

[Bob Lincoln]

I have to ask, just because - any chance you put the thermostat in backwards? Spring faces the engine.

 

[adsjds]

I have to ask, just because - any chance you put the thermostat in backwards? Spring faces the engine.

Nope, I'm careful about that...and this is about the 8th t-stat I've had in this thing. I know the drill by heart.

 

[dana44]

A 1/16ths inch hole will not pass enough water under pressure under any cirumstances to allow that large of a temp movement. Did you have the heater turned on or off during the driving? Want to get all the air out of the system but I don't think that is explaining the low temps, that would be more combustion or lack thereof not putting out enough heat, cold sparkplugs, weak wires or coil, but, colder is better than overheating, right? 10 minutes to warm up to temp does sound about right, but highway temps should be around 180 for the rest of things to function with the O2 sensor.

 

[Bob Lincoln]

Ten minutes is too long to warm up in summer. My car with SuperStat warms up fully in 2 miles of driving, just under 4 minutes.

 

[dana44]

Only other thing I can think would be a cold coil, not having a strong enough spark (or some other weak ignition item), thus running cooler than she should, maybe even sparkplugs a range cold. Not really any other reason she would be running undertemp, or slow to warm up.

 

[John Wood]

I just did a quick read on this thread. Although I think air ingestion is the likely cause for the temperature swings, there is a slight chance that you sender unit could be malfunctioning or that there is a bad ground for the console or temp gauge. This can all be verified with a seperate temperature measuring device.

If the fan is coming on prematurely, you could have a malfunctioning engine temperature sensor (seperate from the gauge sender). Usually a code shows up for the engine temperature sensor, but the gauge sender in the head has no connection to the computer. It is for the gauge only.

Keep in mind that a tiny air pocket in the thermostat housing can really cause problems. Air will insulate not only the T-stat, but the engine coolant sensor.
There are lots of opportunities for air to get to the cooling system including hose clamps, crimp clamps, tiny splits in a hose, bad radiator cap, non-sealing overflow container hose, etc. I would definitely perform a cooling system pressure test.