Keeping a 4.7 cool

[Spjewell]

Warmed up the jeep this evening and got some interesting temp numbers... Seems that my lower radiator hose is hotter than my upper. Please feel free to educate me on the cooling system, but it is my understanding that the coolant is pulled from the lower hose, into the block, then pushed up into the head and out the upper radiator hose.






I believe this indicates that my pump is flowing the wrong direction. This is a flowkooler water pump, does anyone know if they sell one that flows the incorrect direction for a 4.0?

[jasonb]

You're too far away with that thermometer. Try getting the readings within 6" or so.

[Cheromaniac]

You're too far away with that thermometer. Try getting the readings within 6" or so.

What he said. You're standing much too far away to get accurate readings, and Flowkooler only makes a reverse (counterclockwise) rotation pump for a 4.0 since it has a serpentine drivebelt set-up.

[Spjewell]

Took better readings today as pointed out above. Engine was right around 210/215.
Readings were:
Upper hose: 180*+-2*
Lower hose: 170*+-2*

[Cheromaniac]

Sounds like the temp. gauge sending unit might be faulty and causing abnormally high readings.
Your IR gun readings are fine.

[Spjewell]

At the time the readings where taken the temp gauge read around 210. The issue is that the temp won't go down. Lately it seems to idle and maintain temp. Meaning if it indicates 210 it will stay there while idling. If I drive around and get it to about 230 it will stay there while idling.

[Cheromaniac]

Replace the gauge sending unit.

[Spjewell]

Cheromanic, is there a way to test the sending unit? I would like to confirm if the sending unit is infact bad, or if it is an issue with the sending unit wiring. In my swap I had to extend the sending unit wire (the whole OBDI VS OBDII sending unit placement deal) My head is a 99 and my wiring is 95. I relocated my sending unit to be with the computers in the t-stat housing.

Note that the sending unit currently in there was brand new when I assembled the stroker.

Pulled my T-stat flange and did some more testing today and it backs up the incorrect sending unit signal hypothesis.

Gauge indication: 240* F
Upper Hose: 202* F
Lower Hose: 189* F

[jsawduste]

Reading that you have both temp senders in the housing makes me wonder how much restriction there is.

Best place besides the head is the port on the intake side of the block just above the pan rail at about cylinder 3. You can thread a sender there and see more accurately what you temp is. 5/16 square socket plug.

Don't care what the thermostat housing says. I prefer to see what temp the engine is. Thus the block side port.

The FSM has a chart for the sending unit values. You will have to look it up.

I am a strong advocate of factory parts. I use a full factory system and it works just fine.

Back when I was building and selling strokers one caveat was the vehicle be set up with factory cooling parts. Never had any unhappy customers with cooling issues.

[Spjewell]

So you happen to know the npt size on that port?

[jasonb]

3/8 npt

[Spjewell]

Got the new gauge installed. Temps are about 10* better than the factory gauge.. still over heating. Same results on the gun. Warmed it up to ~240, shut it down when the overflow tank started bubbling.

[Cheromaniac]

Like I said before, replace the lower radiator hose with a new one that has a spring in it.

[Spjewell]

Update: been busy so haven't had much time but I finally made some progress. Tracked down a cut to length spring and installed... No change. Talked to a local shop a bit about trouble shooting it for me since I wasent making any progress, and they recommended playing with the fuel pressure... seemed odd since I was allready at 14.7 idle but long story short I added ~20 PSI and now she will keep cool as long as I am moving, runs rich at idle (11:1 to 13:1), but its a starting point. Maybe the computer will adjust? As soon as I get off idle it balances out around 14:1 to 15:1 range, so more tweaking is required. Also ordered a single 16" 2100 CFM fan with shroud to see if this helps it out at idle.

[gonridnu]

I live just outside Las Vegas where summer temps can top 115*. Under normal operating conditions I run right at 210*

I used a Hesco water pump. It utilizes a machined vane impeller instead of a stamped impeller in the FlowKooler. I have had a generic 4 row copper brass radiator in it for years (1800Radiator). I also have an aluminum 3 row I bought but have never installed. I use the NAPA brand Grand Cherokee HD fan clutch and a 2000 and later electric fan. I use a brass Robert Shaw thermostat in a housing I massaged. I also have an aluminum fabricated Renix style expansion tank because the plastic ones break. I used NAPA hoses and run the factory stock auxillary transmission cooler

This summer I am adding hood vents.

None of this was "necessary" for normal operation. It is only for when I am wheeling at slow speeds in the armpit of Hades that I performed all these upgrades.

You have something wrong and my guess is it is the electric fans are not up to the task. I've never personally seen the sense in gaining a few horsepower in a 4wd at the expense of optimal cooling, but everyone seems to be doing it.

If it is overheating at idle I'd look at replacing the fans with the stock mechanical and newer electric w/shrouds. If it is doing it at highway speeds or RPM look at your lower radiator hose.

As a reference point I own a Dodge Cummins as well. Guys on the Cummins site are always doing the electric fan thing and then they overheat when towing. The stock mechanical fan on a Dodge Cummins moves over 12,500 CFM when the clutch is locked up. That is equivalent to 3 of the BEST electric fans out there. Just some food for thought.

I worked at Summit Racing training their tech staff back in the day. I cannot tell you how many hundreds of calls I've taken from guys with electric fans that won't cool their hot rod. You can see all of my mods in my build thread.