Chasing a cooling issue- '85 CFI 5.0/AOD

[Chuck W]

So, I've gotten the '85 Marquis LTS on the road, but have been dealing with a mild "over-heating" issue. It hasn't gotten over 225-230*, but with new cooling system components on a stock 5.0 with a 180* stat, it shouldn't be working hard.

New radiator, stat (180*), water pump, etc. Installed an aftermarket gauge (Stewart-Warner) to monitor the engine temps.

When sitting in the drive, idling/light rev (650-1500 rpm) it'll hold steady at 180-185*. I had it running at 1500rpm in the driveway for 20-30 minutues after swapping the radiator. Stayed right at 180*.
Driving, it does fine for a bit, then it starts to creep up. Coming to a stop and putting it on P or N allows it to stabilize or VERY, VERY, VERY slowly drop.

The car sat for a LONG time before I got it running, and I initially suspected a clogged radiator, but the new one only gave a but more leeway on how long until it starts to warm up.

After checking a few more things (lower rad hose collapsing? Timing off?) and ruling them out, I'm left with a couple other possible culprits. 1. Crud in the engine block or 2. the AOD is running warm and thus heating the engine up.

I'm discounting #1, as after running the car for a bit with the old and new radiators, there is no crud or debris in the coolant. All the stuff I drained for the swap was still bright green and no signs of rust or other junk.

I've been needing to swap out the pan on the AOD, as it had been nicked by a previous owner when they were hacking off the exhaust and has a small hole that is closed with RTV. It's not leaking now, but I have the parts to replace the pan and filter. Just need to take the tie to tackle that nasty job. The transmission doesn't appear to be shifting weird, but it is an AOD and I hate automatics and think they all shift poorly. (Gotta keep this one auto for the wife, though). No slipping or anything when changing gears, though. The level of the fluid looked good and doesn't look terrible. No idea how old it is though.

Seeing as it's heating up while the trans is engaged, I'm thinking the AOD isn't super happy, even though it's not showing any odd behavior. Probably worth a shot to do that filter/fluid service and add an aux cooler to it while I'm in there?

I can't think of anything I'm missing in regards to the cooling system of the engine itself. They're not that complicated...

[emerygt350]

Are you sure the thermostat isn't crap? I have had terrible luck with quickly failing thermostats. Last one died while I was waiting for my aod to be rebuilt. Worked great before I parked it, behaved like you describe after I pulled it out after a year of storage.

I think I have gone through 5 thermostats in the past 7 years. Some within only months of installation.

[Chuck W]

Unless it was bad out of the box, I don't see the stat being the issue. It'll hold stat temp for a long while when the trans hasn't been engaged.

[emerygt350]

I had two that were trash out of the box, wouldn't open completely. I know it's a pita the way the housing is set up but it really is the simplest explanation and I would just pop a new one in to be sure. They just don't make them like they used to.

[emerygt350]

Also, you said you checked the timing, I assume you disconnected the little wire to the tfi?

[OX1]

When I first put stroker in my dad's LTD, we went through 3 motorcraft water pumps.
The impellers were juut falling off the main shaft after couple hours running.

I would check guage agains't aboiling pot of water. Had brand new autometer once that read
super high. Did all kinds of stuff when it really only needed a guage.

Would also do pressure test, see if you have even a super minor leak.

And finally, would use an infrared thermometer. Can measure all the hoses and even different spots on the radiator.
(even waterpump I guess).

[emerygt350]

There is also the tiny chance the thermostat was installed backwards. Again, I would start with the most common, simplest, and cheapest bits.

[Chuck W]

The stat isn't backwards and timing is correct (Been around the EEC 4 stuff a bit). I've waited and felt the stat open. I personally have never run into a bad stat, at least not out of the box, in all of the time I've been wrenching (around 35 years)

No leaks. 16# cap and all of the hoses are hot and well pressurized. The car actually (currently) leaks no fluids at all.

I need to hunt down an IR thermometer to do some spot checks.

[gt4494]

[QUOTE=I need to hunt down an IR thermometer to do some spot checks.[/QUOTE]

Harbor freight carries them inexpensively and they are good enough for what you need.

[BMW Rider]

It does seem that added heat from the transmission could be a factor. Have you considered adding in an auxiliary transmission cooler?

[Chuck W]

It does seem that added heat from the transmission could be a factor. Have you considered adding in an auxiliary transmission cooler?

Got one on the way and was planning on installing it when I replaced the filter/fluid/pan on the trans this weekend.

Grabbed an IR thermometer from work to check a couple temps this evening, but I doubt I'll find any oddities.

[OX1]

It does seem that added heat from the transmission could be a factor. Have you considered adding in an auxiliary transmission cooler?

But could it really raise the engine temp from 180 to 230, unless the trans temp was 300? (and on the verge of blowing up then). Not a huge amount of heat transfer on the stock, in radiator trans cooler, IMO (or not enough to raise engine temp 50 degrees). So even if trans is running hot, not your only problem, me thinks.

[Chuck W]

OK, well I had a moment before dinner to turn the IR thermometer on things. Got the car up to temp and drove it around the block to get it heated up (Was steady at 180* in the driveway). Brought it up to temp until the stat opened up. Verified with the IR that it was running at 180*.

When I pulled back in, it was up to 200* -ish on the gauge. It settled to just under 200* by the time I got the hood up and started checking temps. This was just after a drive around the block (Like 1-2 miles, max. No more than 40-45mph for a short bit). While it was no 220-225*, it still shouldn't have been enough to cause the temp to jump up and then hang there. After 10-15 minutes of idling the temp should drop a bit. Especially when it was 220*+.

At this point, these were the various temps:

- at the intake behind the gauge sensor (stock location) 195*
- at the stat housing - 182*
- at the hot side of the rad - 178*
- at the cool side of the rad - 155* (I checked a few more times and it was a steady 25*-ish drop across the radiator while idling)
- water pump - 160*-ish
- trans cooler fittings - 160*
- T-fittings in the heater hoses - 180-185*

As I let it idle for a bit, the temp behind the sensor dropped to around 192*-ish, while everything else stayed about the same, or cooled by a couple of degrees. The gauge hadn't moved much.

At this point, I'm going to rule out the trans as being a factor. Still going to install the aux cooler, as it's not going to hurt anything.

The stat is a "high flow" version with a bleed on it, so it *shouldn't* be an air pocket.

[gt4494]

did you by chance check the temps on the radiator at different levels? It should be hotter on top and cooler on the bottom. Any big temp changes would indicate a radiator issue.

Just thinking outside the box here.

[Chuck W]

did you by chance check the temps on the radiator at different levels? It should be hotter on top and cooler on the bottom. Any big temp changes would indicate a radiator issue.

Just thinking outside the box here.

I did not, but it is brand new. Like I just put it in this past weekend.

I just checked inlet side vs outlet side.

Besides, it's just a single-pass radiator, it's going to be the same temp top to bottom.

[Chuck W]

I'm beginning to think there *might* be an air pocket in there. That or the aftermarket sender isn't deep enough into the coolant stream.

It's odd that the stat housing, which is 6" away from the sender, in the front coolant passage on the intake, cools, but the area around the sender doesn't really (thus the gauge stays "high"). The cooling system is full, though. Like right to the rad cap full.

This is the first 5.0 I've ever had this kind of issue with.

I think my plan for the weekend is to do a flush on the engine, to make sure there is no residue hiding out in there. Double-check the gauge sender.
Perhaps swap out the stat (with an extra 1/8" hole drilled in it) or run it without one first to see if that helps clear any air pockets.
The car does have some minor rake to it, due to the front springs, so maybe raising the front up a bit might help clear any air bubbles.

[emerygt350]

I would be careful in your temp selection. The cfi is very sensitive to temperatures and if it doesn't get up to 190 they can stay in "cold enrichment" mode.

[mcb82gt]

I always raise the front of the car when burping. I have a small hill at the end of my driveway and I nose the car up there to get the radiator the highest point in the system

[Broncojunkie]

A couple thoughts here. If you're running an oem-style single row radiator, it may not be enough to do the job...depending on changes you've made (cam, headers, gear ratio, etc). Another possibility is that you may have the wrong water pump. You may have a standard rotation but need a reverse rotation or vice-versa.

[conmech]

Unless I missed them....
No mention of fan type, shroud, etc.

Correct rotation water pump?

Try Water Wetter? I've heard nothing but positive words about it.

[Chuck W]

It's a stock '85 CFI 5.0/AOD in the LTS.

New 2-row rad, fan clutch, water pump, stat, hoses, etc. Water pump is proper reverse rotation. Stock fan shroud is in place.

As mentioned, I'm leaning towards an air pocket in the system at this point. I'm wrenching on the car tomorrow, so I'll report back after that.

[Badsmurf]

I have a 91 GT aod car here that does the same thing but slower. I’ve changed the entire cooling system and it still creeps up to 220 after some driving-then magically comes back down as soon as it’s idling/in park. I’m ready to pull the heads and check for blockage in the head gaskets as I haven’t found anything else

[Chuck W]

OK, well today I didn't mess with the aux trans cooler, as it's not really part of the issue.

I did drain out a little coolant and I had the front of the car in the air because I was changing out the AOD filter and pan. After I completed that, I fired things up and let the car come up to temp with the nose in the air. Stat opened up at 180* and I let things run for a bit and added back in more coolant. Satisfied with that and that the trans was properly filled, I went out for a short drive. Took the car 5-6 miles. Got it up to highway speeds, etc and came home.

Once home, the gauge said roughly 220*. I grabbed the IR thermometer and set to checking things. The intake by the sender and the stat housing were both at around 200*, but the gauge said 220*. Still thinking air pocket is the culprit.

I took care of yard work while the car cooled a bit. When I came back to it, I removed the sender, and to my surprise, no coolant came out (I had the car sitting on the ground). The level was 1/2-5/8" below the opening. I did a quick check of the sender in boiling water. The gauge said roughly 210*, so I know the gauge/sender itself is good. I did a quick measurement and found that the sender element is just *barely* into the coolant stream in this location, so it looks like there is kind of an air pocket around the sender. The stock temp switch is a bit longer, so it's not really an issue.

When I put things back together, I poured coolant into the sensor hole before I reinstalled it and jacked up the driver's front corner of the car and let it run again.

It appears that the car is running at about 200*, which is fine, and the issue is with a "dry" temp sender. I need to relocate it, or figure a way to get it better submerged at it's current location.

Since I'm not too fond of the job the clutch fan is doing, I may install an electric one with the 180-200* switch I have. I actually have a manifold assembly that I can fit 2-3 switches/senders in, so I might stick that in the 3/4" heater hose and move the gauge sender and install the fan switch there.

Maybe it'll burp a bit more and the coolant level around the sender will come up, but there is almost a 1/4" difference in length between it and the stock temp switch.

[Chuck W]

Well, I drove the car to work today and things appear to be good.

The car was running around 185* on the interstate stretch of my commute. Once off and back on the surface roads, it crept up to 200* on the gauge and stayed there until I parked the car at the office.

Looks like the air pocket is gone.

[mcb82gt]

So once air purged fully out, the gauge is reading correctly now with the sender in the same location as before?