Hello,

I’ve recently purchased a box truck that is based on a 1999 E350 with a Titan 5.4 V-8. It runs great, heat works fine, fuel mileage seems reasonable, but there’s something I haven’t been able to puzzle out about the cooling system.

Note that in the following description, all quoted temperatures were obtained with a handheld infrared temp gauge. All temps in Fahrenheit.

The engine never seems to get to normal operating temperature. Even after driving 20 miles, the bottom coolant hose is cool to the touch. The top hose reads 100°-125°. Bottom hose reads 75°-90°. Fronts of cylinder banks read 90°-100°. Rear of cylinder banks read 120°-150°.

I initially considered thermostat, though in my experience, a missing or stuck open thermostat will have both radiator hoses running the same temp; the clue is usually that they do that right from the start. Regardless, I couldn’t think of anything else, so I went ahead and replaced the T-stat. The old one looked fine (closed) and this made no difference in running temps.

I’ve tried running it static (parked) at high RPM (not sure how high; it doesn’t have a tach) for close to an hour, with towels covering the radiator. Even in this regime, the highest temps I saw were 150° at the backs of the cylinder banks. I believe my gauge to be accurate, as I can comfortably touch the upper radiator hose at its hottest, and nothing smells or feels hot. I have a decent visceral sense of correct temps, as I worked on import cars for a living for decades. Not familiar with this brand though.

The temp gauge in the dash never moves (other than a little bit when you turn the key on) and I suspect that it is inoperative. So no useful info there.

Thoughts?

Is there some pathway in the cooling system that can bypass the thermostat, of which I am unaware?

Thanks
Andy

 

I don’t know where the heat is going but could the water pump not be flowing to spec?

Sixto
07 E350 5.4 197K miles

 

That occurred to me, but that theory does indeed beg the question of where the heat is going. Also, a guy I talked to at the local dealer, who seemed quite familiar with these, said that he had seen no water pump failures other than leaks.

 

Off the wall thought since I agree the heat has to be going somewhere...

Is it possible that there's some auxiliary heater in the truck box (perhaps custom for a low temperature sensitive cargo)?

I suggest you trace all of the coolant hoses to look for some additional heat removing equipment.

 

That’s a good thought, though I did not see another heater unit in the box. Regardless, I will carefully trace out all the hoses just to make sure that there’s nothing unusual.

 

Stupid question but is your IR thermometer displaying *C or *F? Get the truck on a scanner with live data to see what the ECU sees as coolant temp. If it’s not getting to 180*F or so, the engine will run rich and you’ll get terrible mpg.

Is the clutch fan engaged all the time? That would be really loud. IIRC a good clutch will engage for a few seconds after a cold start then decouple. As they age they don’t engage on cold start but still engage somewhat when hot. In passenger vans, the AC becomes less capable in traffic. But that’s a too hot rather too cold problem.

Sixto
07 E350 5.4 197K miles

 

My IR thermometer readings above are all in Fahrenheit.
I’ll take a closer look at the clutch. I’m used to electric fans, so not 100% clear on how to know if it’s engaged all the time (it would still spin somewhat with the engine, just from drag in the hub, even if disengaged, correct?). I can at least check to be sure that it’s not completely locked up.

 

One way to check is to see if a rolled up newspaper slows the fan or gets shredded.

Sixto
07 E350 5.4 197K miles

 

Ok, some more data based on today’s efforts:

I traced all the coolant hoses, and found no secret extra consumer of heat, other than the engine oil cooler mounted between the block and the oil filter.

I removed the fan completely and ran the engine to see how it would heat up without it, thinking maybe I have a bad fan clutch. 20-25 minutes from cold (right around freezing), with the engine revved up a bit, the backs of the cylinder heads were showing about 177° on the IR thermometer. The top hose was around 155°, and the bottom hose was about 95°. However, the hoses were pretty stiff with pressure, indicating slightly higher temps, so I decided to go old-school, and pulled out my 30 or 40 year old “meat thermometer” type Mac Tools temp gauge and stuck it between the fins on the radiator. It showed 210°! Of course, at that point I shut it down and let it cool.

I took the fan (and clutch) to NAPA to compare the feel of the clutch with a new one. It felt identical. I know that’s nowhere close to a definitive test, but it’s a data point.

I reinstalled the clutch and fan. Right after starting the now-cold engine, the fan was spinning slowly and making no “whooshing” noise. After less than a minute, I could hear the fan speed pick up, and the whooshing started. I slowly inserted a rolled up magazine into the fan (couldn’t find a newspaper). The fan chewed it up a bit, but it was able to stop the fan, and easily hold it stopped while the engine ran. When I released it, it once again took some tens of seconds for the fan to begin spinning at speed and making noise. I repeated this test several times with the same results.

I’m now wondering if I have a problem at all, or if this is just the normal operation of an unloaded engine that’s hooked to a really big cooling system (one that’s sized for the loads of carrying tons of cargo). Especially considering the fact that my IR gauge seems to be reading maybe as much as 30°f low.

In a related matter, my dash coolant temp gauge still doesn’t work. I picked up a new sender for it. This engine has only one temp sender, a two-wire unit under the intake manifold near the forward end of the driver’s side cylinder head. I hooked the new sender to the harness and placed it in a container of 190° water. The gauge still didn’t move, so the problem must be in the wiring or in the gauge cluster. I was just going to install an aftermarket gauge, but couldn’t find an available port into the coolant jacket. Any common easy fixes I should investigate for the inop stock gauge? Or is it usually a bad gauge itself, requiring changing out the cluster?

 

This has to be one of the most unusual situations I remember reading about here on FTE---extremely perplexing!

Double check your IR thermometer but I don't recall reading where they're likely to drift so far out of range they'd read so low. You could use your "meat thermometer" into the degas bottle after the engine has been running a while, see if the coolant is close to the normal operating temperature of approx 192* F.

Typically an unmodified vehicle cooling system will operate close to its design temperature assuming the thermostat is function properly. The coolant will reach the t-stat's design temperature or close to it even in the coldest ambient temperatures. I know my stock E-350 cargo van will take a few miles driving freeway speeds to reach the 195 * F reaching but never the less coolant will reach the engine's design temperatures.

I hope this is easy to resolve but it has me stymied too----good luck and please do update this thread if you find a fix or cure.

 

Use your hands
Long before digital thermometers were developed we had hands
Works for Air conditioner diagnosis too
You have a stuck open thermostat
Replaced with a fail safe?
I do have 3 quick read infrared digital thermometers and a few analog ones
Those are just for me to give my clients a number
The diagnosis is in the hands
That said, with a 195 thermostat, and a working HVAC, I usually see around 192 out of the vents

 

I agree with you on the “hands” thing. I’m fact, it was the input from my hands that convinced me that the engine was hotter than my IR indicated during my fan-removed test.

I’m less convinced of the stuck thermostat theory, given that I have the same symptoms before and after replacing it. That said, I HAVE had new parts be bad out of the box before, so I know it’s possible.

Intriguingly, I do have decent heat output not long after starting the engine. I’ve not yet measured the temperature of the heat output, but my “hand” test says it’s about normal. I’ll quantify it today just for reference, but the fact that I get good heat early calls the thermostat diagnosis into question in my mind.

 

That is why I mentioned Fail safe
Those, if not burped correctly beforehand, will ruin themselves in the first heat cycle (stick open)
If you cannot hold onto the upper hose for more than about 3 seconds when at operating temperature, the thermostat is fine
If that is the case, and you still have no heat, look into the blend door function
Your last sentence says it to me now
If you have decent heat at any time and then none or luke warm after that, it is still not full of coolant
If you go out and turn corners and hit the brakes and accelerate like a jackrabbit and you get some heat
That is another sign of low coolant
Your 99 van should have a degas bottle on it, (a tank with a radiator cap on it right?)
They usually burp easily, you can pull the front tires up on a curb or otherwise elevate the front end and try burping it again
That upper hose should be 192 degrees or so when the engine is at opoerating temp

 

I think there has been a misunderstanding. I have never at any point had trouble with the heater; it has always worked great.

Thanks for the clarification on the Fail Safe Thermostat. I was not familiar with those, and had to look it up. Now I see what you’re talking about there. Yes, this van has the bottle. I’ll try raising the front to see if it burps.

 

So I did do some further testing today. It wasn’t a perfect test, as I changed few variables as it progressed, as noted below, but still some decent data.

Ambient temp 30°F.
I started the engine and just let it idle, and checked temps as time passed as noted below. Note that all temps were taken with my IR thermometer except the heater outlet air temps, which were taken with an analog “meat thermometer” type. Past tests showed these to two thermometers to differ by up to 30°F. Also, all temps in F.

At 5 minutes:
Heater hose 65°
Upper radiator hose 35°
Lower radiator hose cold to touch

At 10 minutes (I turned the heater fan on high at this point, and left it on):
Heater hose 82°
Upper radiator hose 35°
Lower radiator hose cold to touch
Heater output air 98° and rising

At 20 minutes:
Heater hose 84°
Upper radiator hose 45°
Lower radiator hose cold to touch
Heater output air 120°

After taking the 20 minute readings, I revved the engine (maybe 2000-2500 rpm?) and left it there.

At 25 minutes:
Heater hose 100°
Upper radiator hose 90°
Lower radiator hose 47°
Heater output air 150°

At 30 minutes:
Heater hose 120°
Upper radiator hose 120°
Lower radiator hose 65°
Heater output air 160°

So to me it looks as if the thermostat was doing its job of staying closed until about the 25 minute mark, when it opened. Still seems odd to me that the engine didn’t fully come up to temperature and the lower hose get hot, even at 30 minutes, but maybe that’s how it is with a huge-capacity cooling system, the fan spinning all the time (even if not “locked up”) and no load on the engine.

My work experience (from years ago) was with 1970s-1990s European cars that had small radiators (total coolant capacity of entire system of about one gallon) and an electric fan. With those (which also have the thermostat at the bottom of the engine, not the top) the top radiator hose will get hot, then after a while the thermostat will open and the bottom hose will get just as hot as the top. Another little while later, the fan will turn on and run for a few minutes then turn off.