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Need advanced cooling system help!

decathect

NAXJA Forum User
Location
Minnesota
Alright, I am going to be as detailed as possible in describing my issues so that I can solicit as helpful feedback as possible.

My car is a 93 XJ with the stock 4.0L HO (other than a 01 intake manifold and injectors). I recently did a whole slew of upgrades.

Pertinent upgrades and notes:
-Eliminated mechanical fan an installed 2 - 10" fans and 1 9" fan, all electrical. All set up as pullers.
-Installed adjustable thermostat to get fans to kick on at a good temp.
-Installed new 2-row radiator
-Installed an adjustable radiator pipe restrictor as talked about:
Radiator Restrictor
note: this has been set to full open during my recent issues
-Installed aftermarket coolant temp sensor in the stock location in the head, and installed a brand new stock sensor in the heater pipe in the same location as the probe for the adjustable thermostat
-Installed tranny cooler in front of the passenger side of the radiator - same as stock location, though this cooler may be a tad bit bigger.
-Water pump replaced less than 15k ago
-New Stant Superstat 195* thermostat
-Engine compression is good, not losing any coolant.

Issues:
-This setup worked great during the winter and early spring, but now that temps are hitting 80-90 degrees here, my cooling system temperature seems to just rise out of control, even with the fans on.
-At highway speeds temps are just fine, issues are seen only when idling after the car has been driven for a while and is nice and hot.

Questions:
-Here is the weird thing. Temps on the head only reach around 208* at worst, but the temps from the heater pipe, on the stock sensor/gauge, seem to indicate like 225*+. Which one should I go by? Heater pipe seems to be about 10-15 degrees higher.
-Should I not be worried, since temps on the head still stay under 210? When I'm moving on the freeway they stay right around 195. I haven't even started to use my A/C yet, I imagine that will only make the problem much worse. Turning on the heat helps, but this is obviously a bit uncomfortable.
-Has that big trans cooler killed the air flow through my radiator?
-What can I do to fix this? Install pusher fans in front, in addition to the puller fans? Will that do anything? Vent in the hood? That seems unecessary.

I'm just sort of at a loss as to what the obvious fix is here. Any help or suggestions are greatly appreciated!


Pictures:
This is an example of the temp taken from the head:
sdc10834r.jpg


This is the temp from the heater pipe:
sdc10833n.jpg


E Fans:
sdc10835h.jpg


Restrictor:
sdc10836e.jpg


Thermostat probe and location of stock sensor (grounded):
sdc10837.jpg


Engine Bay:
sdc10838b.jpg


Grille area, you can see the trans cooler:
sdc10842.jpg
 
Sensors aren't exact and will vary by +/- 15 degrees easily. Also the brass thing on the upper hose is going to be affected by the environment--when fans are blowing it will wick heat pretty quickly, and when A/C compressor is engaged it will probably absorb heat. Keep in mind that you are monitoring coolant temp not engine temp. If you want to know the real temperature get an IR gun and read the thermostat housing while comparing to the other temperature readings.
 
Alright, I am going to be as detailed as possible in describing my issues so that I can solicit as helpful feedback as possible.

Nice job of outlining the vehicle for easier understanding ..... soooooo much better than the usual forum readings ..... "my XJ runs hot --- help " :rolleyes:

Issues:
-This setup worked great during the winter and early spring, but now that temps are hitting 80-90 degrees here, my cooling system temperature seems to just rise out of control, even with the fans on.
-At highway speeds temps are just fine, issues are seen only when idling after the car has been driven for a while and is nice and hot.

Hotter summer temps / idling wont provide the ambient temp / windchill factor on the radiator that the winter temps did - so the coolant temp at the radiator outlet will be hotter.

Dont know what activation temps you have the thermo fans set up at ... but I would suggest lowering the temp setting that the ones not controlled by the computer, come on at ... even better - have those fans controlled by a sensor on the radiator outlet.

Situation then is ... Start vehicle from cold ... when engine temp is at 195'f approx - set aftermarket fan controller to activate ... that way the fans will always come on at the temp the bottom outlet coolant temp was ... ( 150'f as an example ) .... regardless of what the engine temp sensor displays on future occaisions.

That will ensure the radiator is providing sufficiently cool liquid for the thermostat to play with, to provide a constant engine temp, relevant to the stamped temp setting on the thermostat .... If the CFM of the fans is enough at low speeds.

Much better than an overheating situation activating the fans - as the factory setup does.

Questions:
-Here is the weird thing. Temps on the head only reach around 208* at worst, but the temps from the heater pipe, on the stock sensor/gauge, seem to indicate like 225*+. Which one should I go by? Heater pipe seems to be about 10-15 degrees higher.
-Should I not be worried, since temps on the head still stay under 210? When I'm moving on the freeway they stay right around 195. I haven't even started to use my A/C yet, I imagine that will only make the problem much worse. Turning on the heat helps, but this is obviously a bit uncomfortable.
-Has that big trans cooler killed the air flow through my radiator?
-What can I do to fix this? Install pusher fans in front, in addition to the puller fans? Will that do anything? Vent in the hood? That seems unecessary.

As ehall said .... Heater hose temps are probably being affected by the ambient temp under the bonnet ( oooops ... hood ... :) )

Personally ... I'd be fitting the coolant temp sensor in the thermostat housing or the top hose ... rather than the heater hose.

I wouldnt be too worried all up tho ..... apart from the ability of the fans to do the job properly.

If you have an engine block temp sensor which displays whats really going on .... Just get used to your new, "normal" coolant temp of 225'f as displayed by the heater hose sensor ... lol

Getting some IR temp readouts as comparisons would also ensure you are comfortable with the setup ..... as ehall suggested too.

20'f+ hotter temps than the engine certainly explains why the heater / demister works so well though .... LOL

Large oil cooler may cause airflow obstruction ... but you stated your temps are OK at your highway speeds ... so its more likely that there is not enough CFM drawn by the electric fans, early enough, to keep the radiator coolant temps down.

I'm just sort of at a loss as to what the obvious fix is here. Any help or suggestions are greatly appreciated!

Ensure the fans are drawing enough CFM when needed ... get them activating ( cooling ) sooner, and see what the temp gauge results are.

A lower temp thermostat will also allow more of the coolant held in the engine to be released earlier, for cooling in the radiator ... If you wish to go down that path frowned upon by most ... but happily used by those who understand the process - and what to expect.

In regard to your "restrictor" .... Im not in favour of them .... its like fancy steering dampers to alleviate DW .... just hides the real problem. In your case, even having it wide open - really doesnt help if the fans arent cooling the radiator properly at low speeds ... It just means full flow of coolant, that is too hot to be of real benefit.

Hood Vents .... banged in the middle of the bonnet are, as you said .... "unnescessary" IMHO .... Does no more than the equivalent of putting a bigger chimney over a fireplace - when all that was really needed, was to turn the fire down .... or in the case of the XJ - lower the engine operating temp.

Some vents in the rear corners of the bonnet will certainly help create a draft through the engine bay tho .... allowing possibly better radiator air inflow ... and an escape route for hot air which builds up in the rear corners.

Im a cheapskate tho ....... so just have 1/2" bonnet hinge spacers and insulation across the centre, at the firewall.


The centre of the bonnet btw ... will always be hot .... Main reason being the the engine and heater hoses are only about a 1/4' below the bonnet ... in addition to all the other reasons. ;)


:cheers:
 
Hm.

Given your CHT readings, it doesn't sound like you're that far out of line. Bear in mind that ECT readings aren't going to be anywhere near engine temperature!

My first thought? Go pick up a bottle of Water Wetter and dump it in. Small bottle - about 12oz or so.

Water Wetter is a surfactant, which means it breaks down surface tension (making the water, er, "wetter." By breaking down the surface tension of the water, it will make surfaces "wetter" than it otherwise would. For a demonstration of surface tension, look up that old fifth-grade physical sciences experiment where you float a needle on the surface of a cup of water...)

Since the water is now wetter, it will make more intimate contact with the internal engine surfaces (allowing it to pick up more heat) and with the inside of the radiator tubes (allowing it to reject more heat.) I love this stuff, and absolutely swear by it! I have found it particularly useful in stationary equipment (generators and pumping engines,) where all you get is the airflow caused by the fan - unless you happen to have the wind going in the right direction.

Your OEM ECU sensor should be installed in the thermostat housing, so that's the temperature your ECU will "see" (the one in the rear of the head is used to drive the gage - and it will likely read hotter than the one up front anyhow. It's in a "flow pocket" back there, and serves as more of an "early warning indicator" than an actual indicator of engine temperature. If you install hood spacers at the hinges, you'll probably see that reading decline slightly as well.)
 
X2 the water wetter awesome stuff

those fans have enough cfm?

Cooler is plate type or radiator type?

Lose the restrictor

225 isn't that hot. Pressure test system to be safe.
 
Sensors aren't exact and will vary by +/- 15 degrees easily. Also the brass thing on the upper hose is going to be affected by the environment--when fans are blowing it will wick heat pretty quickly, and when A/C compressor is engaged it will probably absorb heat. Keep in mind that you are monitoring coolant temp not engine temp. If you want to know the real temperature get an IR gun and read the thermostat housing while comparing to the other temperature readings.

Ah, I love this forum. You guys are so much more helpful than JF people.

yeah, I have actually compared gun readings, and i think the thermostat housing is quite near what the heater hose sensor reading was, maybe a tad bit lower. I will check those again though, good suggestion.

I have been meaning to wrap that copper stuff in insulation as well, maybe I will do that soon.

I am thinking perhaps the fans don't pull enough CFM... grr. Any suggestions of good brands that make super high flowing fans? I might add a pusher or 2 on the front, if i can fit them behind the grille.

I will grab some water wetter, perhaps space out the hood (as a temporary fix), and eliminate the restrictor (even though its on full open, maybe it is still restricting flow...)

oh and note, I do still have the stock ECU sensor in the thermostat housing... the one I relocated was the gauge switch that was originally in the back of the head.
 
Last edited:
oh, sorry, forgot to answer that. Right now they are set to come on really low... like 180*. I did that just to make sure that the turn-on point wasn't the issue.
 
oh, sorry, forgot to answer that. Right now they are set to come on really low... like 180*. I did that just to make sure that the turn-on point wasn't the issue.

Try lowering the activation temp .... Wont cost you anything but time to check the result ... no point buying new / changing your fan system if you dont need to.

I'd wind em back to 100'f activation for starters and see if it helps - and adjust as nescessary. The fans may be more able to maintain temps from a lower setting compared to trying to cool down already heated coolant.

Personally I'd go back to a quality clutchfan unless you have a need to shut down the fans due to water crossing etc.

Additionally ... If your current coolant temp at the thermostat housing does turn out to be a constant 225'f.

1/... Thats 15'f higher than what so many are willing to accept as "normal" .... and ....

2/... It's also 30'f higher than the stamped/indicated temperature operation of the original factory supplied thermostat.
 
Carves, I've also tried having the fan on continuously, and even when starting from a lower temp, the fans are unable to keep the temps in an acceptable range.

Unfortunately i have permanently disabled my clutch fan, but I am willing to spend extra on a better quality e-fan if that will help, I just haven't received any suggestions on that yet.
 
Carves, I've also tried having the fan on continuously, and even when starting from a lower temp, the fans are unable to keep the temps in an acceptable range.

Unfortunately i have permanently disabled my clutch fan, but I am willing to spend extra on a better quality e-fan if that will help, I just haven't received any suggestions on that yet.

Ahhhhh ..... Then that would indicate that there isnt enough, fan CFM draw, for slow speed operation in warmer weather.

That taurus fan mod, seems to be the most successful conversion for those desiring all electric, fan setups ... but thats from what I've read, not experience .... as correctly functioning clutchfans have been enough for my driving requirements.

Hope you get it sorted.
 
Yeah, i'm starting to think the fans just aren't powerful enough... shame, as I thought 3 of them would be more than enough. I've used just 1 on other cars with great results. Guess you're right, the XJ cooling system is just very demanding.
 
The stock system with a good upgraded radiator has worked perfectly for most of us.......even with stroker motors and big lifts and tires. Also, while I've never tried it myself, some that have gone to dual electric fans eventually went back to the mechanical fan due to not enough air flow.
 
I think you need a minimum 3k cfm total to make the e-fan conversion work in warmer climates, and this must be well shrouded. Your pics look as though you've probably got this covered, but possibly not. Didn't see where you had listed using a new 16lb. radiator cap or had pressure tested the system, but you've probably got that covered as well. Might want to verify cfm and pressure test again.
 
what do you mean, a mechanical temp gauge?

From your photos I see you have two temp guages, the digital one high on the dash next to the GPS and the stock one in the dash. These are electrical gauges that have a thermistor located in the cooling system that usually provides a ground for the circuit, with the load being the guage. The electrical circuit could pick up resistance from a bad connection/splice or a dirty and corroded connection (esp the stock one) that provides a false reading.

A mechanical gauge is a thermometer. The probe is connected by capillary tube to the gauge. Old school was filled by mercury, not sure what element fills the newer gauge's capillarys. As the temp heats up the element inside the capillary expands and the needle reacts. The gauge is calibrated, not 100% calibrated, but more reliable than an electrical guage.

The capillary must be kept sealed ant not kinked.
 
Your fans will be far more effective if mounted on a suitable shroud. You should have at least an inch between the center part of the fan blade and teh radiator core. Second, I would use only an auxiliary trans fluid cooler and not run the tranny fluid through the radiator, mount the aux cooler to the backside of the radiator, the temp of the air coming through the driver side of the radiator should be adequate to cool the tranny fluid. I have tried without success to find a smaller water pump pulley but if you can find one it will improve your low RPM coolant flow.
 
From your photos I see you have two temp guages, the digital one high on the dash next to the GPS and the stock one in the dash. These are electrical gauges that have a thermistor located in the cooling system that usually provides a ground for the circuit, with the load being the guage. The electrical circuit could pick up resistance from a bad connection/splice or a dirty and corroded connection (esp the stock one) that provides a false reading.

A mechanical gauge is a thermometer. The probe is connected by capillary tube to the gauge. Old school was filled by mercury, not sure what element fills the newer gauge's capillarys. As the temp heats up the element inside the capillary expands and the needle reacts. The gauge is calibrated, not 100% calibrated, but more reliable than an electrical guage.

The capillary must be kept sealed ant not kinked.
Might just be me, but I thought that's what that single-wire coiled up silver thermostat line was. It looks like either a thermocouple lead or a capillary for the type of thermometer you explained, either way, should be independent of the engine block ground.
 
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