3.0 Doesn't Get Up To Operating Temp After Coolant Flush

[97Ranger3.0]

Hey guys,

I recently did a coolant flush on my 97 3.0. While I was doing the coolant flush, I replaced the thermostat with a new one from NAPA (OE temp). The original one seemed to be working, but I figured why not swap it out while I was flushing the system anyway. However, ever since then, the truck has trouble getting up to temperature when its around say 60 degrees or below. It will just get up to where the needle points right on, or just above, the "C" on the temp gauge and stay there steady. It will only get up to operating temp if I sit idling for quite a while, but then once I start moving again it drops right back down. Of course, it's worse when it's even colder, but thankfully it gets warm enough still to get heat. I'm not sure exactly what temperature the truck gets to, but I will hook up my scan tool next time I drive and see what temp it stays at now.

Anyway, what I'm wondering is, is this normal for the 3.0 with a nice clean cooling system to run a bit colder? I believe I'd read something before about 2.3's having this issue and people blocking off their radiator with cardboard to get heat in the winter. So I'm just wondering if it is common for 3.0's to have trouble getting up to operating temp with a good cooling system. Or, if I just got a faulty thermostat. I just figured I'd ask before I go swapping out the thermostat again or even trying to test the thermostat since either way I would need to take it out.

 

[Dirtman]

If it still makes heat in Massachusetts weather i would not be concerned. It's possible your old coolant was doing a crap job and now you're seeing the system work as it should.

Getting a reading from the PCM via a scan tool is an excellent idea, the computer is on a different sensor than the dash guage so you can verify the guage.

Also worth checking that the fan clutch isn't locked up.

 

[Alan_nc]

Well my 94, 3.0, auto which has a pretty clean system and runs fine takes awhile to heat up and the guage never gets past 1/4. I have replaced the temp sending unit and the thermostate within the past 90 days.

 

[97Ranger3.0]

Thanks for the replies guys.

I should've mentioned I have an electric fan conversion as well. (I did it properly with a temp switch in the upper radiator hose so it's not running constantly either.) So no issues with a mechanical fan and fan clutch.

The old coolant was definitely pretty gross, and it took quite a few rounds of running straight water and flushing chemicals in it to get it clean before filling it back up with coolant. That's why I wanted to ask before I assumed the thermostat just happened to be bad out of the box, since I'm sure that the cooling system is more effective now.

I did take it for a test drive with a scanner hooked up. The temp stayed around 165. (Also it was 55 outside at the time). The only time the temp rose above 170 was when I pulled over to turn around. But again, once I started driving again it dropped back down pretty quick.

That seems a little low to me, but it sounds similar to how Alan_nc said his truck behaves. So maybe the old coolant really just was that bad

 

[Shadowrider6661]

Thank you for your service ! I have the same issue with my 97 since I replaced the engine and radiator. The only time the temperature goes up is when I'm pulling a trailer, other than that, it runs between 100°- 120°. I haven't been able to get it to operate at what's considered normal. The radiator is the largest one that's made for my truck and the original engine needed the bigger radiator so that's what I put back in. I'm only telling you about my trucks heating issues so that you know that it happens to others as well. Myself, I plan on making a cover for my radiator if the need arises, something that is easily detached if not needed. Have a great day.

 

[Shran]

Kind of sounds to me like the thermostat is stuck open, the coolant is just flowing through it and not staying in the engine long enough to get hot.

Old coolant doesn't really lose its ability to transfer heat though, I don't buy that at all. As long as it's (1) moving, (2) not contaminated to the point that it's mud, and (3) not getting stuck in an area due to a restriction in the cooling system, it will pull heat out of the block.

I could see a situation where if it was very cold and the radiator was uncovered with cold air flowing through it, you may never see normal operating temp. But at 55 degrees you should be at operating temp pretty fast.

 

[Alan_nc]

I don't know the other guys but I really don't consider it a problem. I get plenty of heat. Does take maybe 3 to 4 miles before I've got heat. Once you are up to (whatever temp the thermostate is set to open at) it stays full open for the rest of the time. I guess it is possible that it never closes but since I get heat in 3, 4 miles I don't see it as a problem.

 

[97Ranger3.0]

Kind of sounds to me like the thermostat is stuck open, the coolant is just flowing through it and not staying in the engine long enough to get hot.

Old coolant doesn't really lose its ability to transfer heat though, I don't buy that at all. As long as it's (1) moving, (2) not contaminated to the point that it's mud, and (3) not getting stuck in an area due to a restriction in the cooling system, it will pull heat out of the block.

I could see a situation where if it was very cold and the radiator was uncovered with cold air flowing through it, you may never see normal operating temp. But at 55 degrees you should be at operating temp pretty fast.

Well, that's a good point. When I flushed my coolant it was discolored and there was some occasional gunk in it, but nothing crazy. So it definitely wasn't mud by any means lol, just dirty.

I also agree, I would think that at 55 degrees it should get up to operating temperature. For what it's worth, I've now had the truck going on almost 4 years. I've replaced the coolant in the truck before, like when I replaced the timing cover gasket & water pump due to leaks. At the time I didn't flush it out, I just drained the old stuff out and put in fresh coolant. The truck always got up to temp even on the coldest winter days both before and after doing that work. It wasn't until I did the recent flush (which did clean the system pretty well) and replace the thermostat that this started happening. I would say that since then, it doesn't stay at the operating temperature unless its 70 degrees or above. Even in the 60-70 ambient temp degree range the temp gauge will show around 1/4 of the way up (I'm guessing around 180) and the e-fan rarely even kicks on anymore.

Also, I know that since I still get heat and all that it's not a major concern. But, if it's running too cold (especially on really cold days) then I might be wasting fuel because it'll still be running richer.

 

[55trucker]

Pull the stat out again, have a close look at it for debris jammed in the valve passage, if you doubt the stat itself place it into a pot of water & let the water come up to a boil, attach a candy thermometer to the edge of the pot & monitor the temp at which the stat begins to open.

 

[Roert42]

I have put 5 parts store thermostats in various vehicles over the past few years. Every single one was junk. Replace a thermostat 2-3 times then buy a motorcraft one and the problems go away.


However, every single time is been a overheating problem. Stuck closed boiling coolant, even in the dead of winter.

 

[Rearanger]

I should've mentioned I have an electric fan conversion as well. (I did it properly with a temp switch in the upper radiator hose so it's not running constantly either.)

I did an eFan conversion as well. I think you'll find the temp switch works better in lower rad hose.

The reason I did the eFan was what your issues are - low running temp. I installed a digital heat gauge and found the engine not getting to factory heat. Everything is original stock save for the fan. The eFan helped but did not completely cure the low temp.

I did take it for a test drive with a scanner hooked up. The temp stayed around 165. (Also it was 55 outside at the time). The only time the temp rose above 170 was when I pulled over to turn around. But again, once I started driving again it dropped back down pretty quick.

I also used a piece of foam plumbing pipe insulation on the by-pass hose to retain heat. My running temps are higher than yours by about 10 -15 degrees, but not the 195* I think it should be. The ECT sensor runs about 5* hotter than the gauge sender at the stat.

 

[97Ranger3.0]

I have put 5 parts store thermostats in various vehicles over the past few years. Every single one was junk. Replace a thermostat 2-3 times then buy a motorcraft one and the problems go away.


However, every single time is been a overheating problem. Stuck closed boiling coolant, even in the dead of winter.

Huh, good to know. That was why I bought mine at NAPA, I seem to only have good luck with their parts vs the other parts stores. I think the NAPA one I got was still a motorad brand though, so probably the same brand all the other stores carry. If I do decide to swap it out, I'll just get a motorcraft if I can.

I did an eFan conversion as well. I think you'll find the temp switch works better in lower rad hose.

The reason I did the eFan was what your issues are - low running temp. I installed a digital heat gauge and found the engine not getting to factory heat. Everything is original stock save for the fan. The eFan helped but did not completely cure the low temp.



I also used a piece of foam plumbing pipe insulation on the by-pass hose to retain heat. My running temps are higher than yours by about 10 -15 degrees, but not the 195* I think it should be. The ECT sensor runs about 5* hotter than the gauge sender at the stat.

How come you say the temp switch works better in the lower rad hose? Just curious. I installed it in the upper hose because all of the articles I found here on TRS and other similar websites said to do so. It also would make sense to me in the case of the 3.0 to have it in the upper radiator hose because it's closest to the thermostat. I might be mistaken, but wouldn't the upper hose be the hot coolant going into the radiator, and the lower is the cooler coolant heading back to the engine? If so, wouldn't having it in the lower hose cause the fan to kick on later, or essentially at a higher temperature because it is seeing cooler coolant? Again, I might be mistaken and it could be reversed, I'm just guessing the upper hose is the inlet because that's what comes off the thermostat housing.

Pull the stat out again, have a close look at it for debris jammed in the valve passage, if you doubt the stat itself place it into a pot of water & let the water come up to a boil, attach a candy thermometer to the edge of the pot & monitor the temp at which the stat begins to open.

Well I thought about that, but I feel like if I go through and drain some coolant and remove the thermostat, I might as well just put a new one back in its place lol. I could always test it after the fact though to confirm it wasn't functioning properly, or test the new one before it goes in though.

 

[Roert42]

The fan helps control the temp of the radiator. if you have the switch on the outlet then the fan comes on when when the radiator alone can not provide enough cooling.

If the switch is on the hot side then the fan can potentially come on when the extra cooling is not needed, causing the engine to run cool all the time.

 

[Rearanger]

How come you say the temp switch works better in the lower rad hose?

I went back and forth about where to locate the temp sensor but finally decided I only cared about the temp after the rad because if the rad was cooling I don't need the fan on. As well my Camry has the fan switch in the lower hose.

 

[Orca]

Well I thought about that, but I feel like if I go through and drain some coolant and remove the thermostat, I might as well just put a new one back in its place lol. I could always test it after the fact though to confirm it wasn't functioning properly, or test the new one before it goes in though.

The easiest way of all, assuming your scantool can graph, is to graph the ECT (Engine Coolant Temperature) as the engine warms up from a cold start. If the thermostat is working correctly, you'll see a distinct drop in ECT when it opens. If the thermostat is stuck open, there will be no such obvious drop in the graphed line.

You might be able to detect it even if your scantool cannot graph, but it's harder.

Failing that, just feel the hoses while warming the engine. If the thermostat is working correctly, then the return line to the radiator should be relatively cold until the thermostat opens, after which it'll get quite hot, rather quickly. (You can still use a non-graphing scantool here to anticipate when the thermostat should start to open, based on ECT value versus the thermostat's set point.) If instead that return line gets slowly and progressively warmer, the thermostat is stuck open.

Pulling the thermostat should really be the last option, IMHO.