2001 Grand Marquis Overheating

[SwampSurvivor]

I'm at a loss here. This is my 2001 Grand Marquis , 175K miles on the car ... 160K miles on engine.

I noticed this spring/summer that the fan was running pretty much constantly. According to the torque app, it was running around 225 on the highway. If sitting still, it would cool down.

When I got the car 5 years ago, I'm pretty confident I was the first person to ever change the coolant. Numerous coolant flushes and it still turns brown quickly. But it never had any overheating issues. It always seemed to run right around 200 -210 and I never heard the fan come on unless I turned on AC

This year it's been worse. We had a day last week where it was 100F out and it couldn't keep up. Even with the heat on full blast, best it could do was 235. It kept going into failsafe cooling mode if I didn't have the heat on full blast. That means it was hitting 260... Even when it hit 260, the coolant wasn't boiling but I could tell it was HOT. There's 2 temp sensors - one of the gauge and one for the computer. If they're both agreeing that something hot, I'd be inclined to believe that it's not a bad sensor.

I put a new 195 degree thermostat in. Didn't help. Changed the water pump and radiator and same problem.

It's not boiling the coolant or using any coolant. No milkshake in oil or on the oil cap ... not that oil cap is a good indication on a 2 valve Ford anyway - they always milkshake the oil cap). The weird thing is, yesterday when it was running at 230, I was able to squeeze the upper radiator hose and opened up the cap and it didn't even have any pressure on it?!

There is definitely coolant flow. Heater is blowing hot. Old water pump was perfectly fine. When I pulled the radiator, I back flushed it a bit and got a bunch of crap out of it.

If I put my hand over the new radiator, I can tell it's definitely doing something. Warm on the driver's side, cool on the passenger side.

 

[Kestas]

For starters, find out why it's not building up pressure. There has to be a leak somewhere. Check the radiator cap. Introduce some pressure with compressed air, using no more than 20 psi. Splash soapy water at suspect areas. Pressure reduces the incidence of nucleant boiling in the system. Nucleant boiling reduces heat transfer.

Your next step may be to clean out the cooling system using a citric acid flush. Follow directions so you won't get too aggressive with the chemical. Be forewarned that this may also uncover a leak in your radiator. Sometimes scale is the only thing keeping it from leaking.

 

[crashz]

The weird thing is, yesterday when it was running at 230, I was able to squeeze the upper radiator hose and opened up the cap and it didn't even have any pressure on it?!

This is strange. I would expect it to feel pressurized and be too hot to touch with your bare hand. I would also expect the radiator to be too hot to touch, anywhere. Something flow related if I was to guess. Maybe the new T stat is not opening? Lots of complaints about aftermarket stuff.

Edit - could the system be air-bound?

 

[Chris142]

There's no way that you had no pressure and 230F. It would have been puking coolant.

 

[SwampSurvivor]

This is strange. I would expect it to feel pressurized and be too hot to touch with your bare hand. I would also expect the radiator to be too hot to touch, anywhere. Something flow related if I was to guess. Maybe the new T stat is not opening? Lots of complaints about aftermarket stuff.

Edit - could the system be air-bound?

I couldn't touch the upper radiator hose it was so hot. I believe coolant was flowing past the thermostat. Maybe I'll try another thermostat.

I was thinking there was the potential for it to be airbound. The cooling system is very similar to the one on my truck .. as I learned with that a few years ago if that gets airbound it blows the lower hose off. I've changed the engine and the hoses and never had issues with it getting a bubble that wouldn't burp.

 

[SwampSurvivor]

For starters, find out why it's not building up pressure. There has to be a leak somewhere. Check the radiator cap. Introduce some pressure with compressed air, using no more than 20 psi. Splash soapy water at suspect areas. Pressure reduces the incidence of nucleant boiling in the system, which reduces heat transfer.

Your next step may be to clean out the cooling system using a citric acid flush. Follow directions so you won't get too aggressive with the chemical. Be forewarned that this may also uncover a leak in your radiator. Sometimes scale is the only thing keeping it from leaking.

The citrix acid flush scares me. I don't want to eat a 25 year old heater core. That would be the end of the vehicle. I guess I could just bypass it temporarily.

 

[supton]

I'm thinking it's the radiator, it's somehow plugged up, not actually flowing. I wonder if you could get one of those borescopes and see what can be seen in the tanks? but it could be plugged elsewhere.

 

[AandPDan]

You changed the radiator, with new or used? If new, does it have the correct number of rows? Is there an electric or mechanical fan? If mechanical is the fan clutch working? Shrouds in place?

 

[Marcozi]

Use an infrared thermometer on the upper and lower hoses. Report the difference.

 

[JohnnyG]

Make sure that the lower rad hose is not collapsing when hot and under suction.

 

[Toyotech454]

The lack of system pressure is your strongest symptom to start investigating

 

[We're Metals]

Intake Manifold

 

[Dadillac]

Start simple first. I would check the temp sensor first. If it can be done easily get a mechanical gauge in there and see what happens.

Don

 

[supton]

Ack, I missed that it got a new rad. Seems it's had the parts tossed at it... I wonder, can you take the old t-stat and gut it? If the heater blows hot and can actually cool the motor down, then the water pump is likely working (I guess it could be still deficient in flow), but I wonder if it's just not pumping through the rad for some reason. Maybe bad cap? I think I had a bad one once and it would overheat randomly. But dad's van, we kept the cap on the first click to prevent it from building pressure (due to a slow leak) and it did fine for a few years.

 

[nascarnation]

Use an infrared thermometer on the upper and lower hoses. Report the difference.

Wisdom. And that's a 15 dollar tool that can help diagnose a LOT of systems.