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'87 Shelby CSX: electric fan got sticky, now overheating

Engine 
2K views 10 replies 4 participants last post by  helpful_hw_man 
#1 ·
I noticed my fan noise wasn't normal any more, and after a 20 mile drive at 75mph (with AC on), I pulled up the hill into home and my coolant overflow was steaming and coolant was boiling. I gently cooled off the radiator, then the lower block, then the head and intake with a garden hose sprayer and got the temp down. Not sure if that was smart or not, because it's an aluminum head and the block-head interface cools at different rates. The head stayed hot the longest.

With ignition on, engine off, the coolant gauge was pegged on the dash. I forgot about the fan noise and was worrying about a coolant leak, and had been watching the speedometer, not the coolant temp on that drive. I think the temp got up there (with no fan assist) towards the end of the drive.

I waited a day, put in about a half-gallon of 50/50 coolant/water, then did a restart; there was no coolant leaking, no bubbling, and one short test drive seemed okay. A longer drive to a HW store had the temp gauge climbing to 3/4, so I let the car cool down again.

That's when I remembered about the fan, and it was real stiff but freed up and sounds crunchy. I bought some penetrating tri-flow spray at the HW store and lubed the fan shaft the best I could. It's still crunchy, but should engage. Yet it didn't...

I will need to test the coolant temp sensor and backprobe it, because the fan doesn't seem to be engaging. There could be a fuse involved too.

The drive home involved 1500 feet of gain; I drove slow,but had bubbling coolant again (not as bad as the first time) and the block cooled pretty quickly this time with the hose. No/minimal loss of coolant on the second episode, temp gauge didn't peg.

I know I could be looking at a head gasket issue as a result of this fan failure, possibly a thermostat too.

The thermostat was replaced a few years ago, and I re-did the water pump after that. I don't think the mechanic drilled a hole but I've always been able to burp the upper hose to get a good fill.

What temperature should the thermostat be rated for? The radiator cap is also a suspect. All these parts are cheap, no sense risking another failure.

Another question I have is what the expected fan function and temperature should be. It's been cool at night, maybe 80 during the day. NAJ had made a chart that showed the fan kicking in at CTS 2.1v (212 degrees) when letting an idling car sit.

For those with daily drivers, is your fan coming on in 80 degree weather if you have the AC running, and how high does your dash temp gauge read at that point?
 
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#2 ·
To cool the engine you only need to spray the radiator with cool water and the coolant in the engine and rad will flow all by itself and cool naturally.
(Hot always moves to cold)

Fan comes on at 212 degrees, shuts off at approx 195 +/- degrees.
The cooling fan should be on whenever the A/C is on and the compressor clutch is engaged.
If you want to know actual engine temp backprobe the Coolant Tamp Sensor and read the voltage.

If the fan is not coming on at the proper temp or with the A/C on check to see if you have power (12 volts minimum) at the cooling fan motor.
1)Unplug the cooling fan connector.
2)Using a digital voltmeter probe the LT GN wire on the harness side.
3)Start the engine and with the engine running disconnect the CTS connector.
4)CEL/Power Loss lamp should illuminate and power should be present on the LT GN wire. (This will set a Code 22 in memory)
5)If power is not present...
Diagnose the Cooling Fan Relay circuit.
6)If power is present...
a)Shut the engine off
b)Reconnect the CTS and cooling fan connectors
c)Start the engine and again disconnect the CTS connector.
d)Did the cooling fan come on?
e)If NO, verify the BK ground wire has continuity to ground.
f)If OK, replace the cooling fan motor.



 
#3 ·
A few notes: If your fan makes crunchy sounds when you spin the blades, it's probably worn out/toast. Possible it sucked up some trash but that's not common. What typically happens is the bearing wears out or the brushes wear out. The fan is not serviceable unless you remove it and send it to a small electrics motor repair center, not easy to find any more. Typically when they get to the point of making that type of noise, the circuit may be working but the fan will not run. In some cases, the fan will run a lot of current through the wiring and it can cook the wiring on the fan side of the relay. The relays are incredibly durable and typically will survive the heat generated from extra current caused by poor connections and fans that are going kaput.

I fan that is worn out typically will not run (duh) when the coolant temp sensor is disconnected or the AC is turned on...but it can overheat the wiring and potentially cause shorts in the front engine harness so its a good idea to unplug an inoperative fan and avoid stop and go traffic and/or using the AC.

If you have to open the radiator cap to add coolant, you might also have to bleed the cooling system to get it full and remove any trapped air in the head. This process is pretty well documented on this site, use search for 'bleeding cooling system'.

Anytime the head is replaced, you replace the thermostat. It's like an $8 item. I just last month had to replace a thermostat that was about 1 year old because the car was running hot almost all the time, not in the red, but hot enough to cause the 16psi radiator cap to blow into the recovery bottle. Normally runs hot all the time is a radiator, restriction in flow, or a head gasket issue. I didnt have any symptoms of a head gasket and the radiator seemed to be flowing quite well. A $8 thermostat fixed that problem, and I went with the 195* instead of the 180*. Either will work fine. I think I am going to replace the 195* with the 180* just to keep the engine a few degrees cooler though. If you replace the thermostat, check to see if it comes with the small bleed hole modification. Many do now, if not, add a bleed hole and mount it with the hole at the top when installed in the head. This helps coolant leak past when you fill the radiator, and can sometimes avoid trying to bleed the system. Its a slow leak because the hole is small so you have to be a little patient when trying to get all the coolant in that it can hold.

50/50 is the best mix, 100% coolant will make the car run hotter! Pure distilled water is best and runs cooler than 50/50 but lacks the anti-deposit ingredients and lubricants that are good for water pump seals and bearings. Coolant actually looses its anti-corrosion and deposit additives after 12 months, that is why it should be changed every year. It still cools, but the additives become ineffective after 12 months.

I hope this helps answers some of your questions.
 
#5 ·
I'm further along in diagnostics. I backprobed the coolant temp sensor (I've done this before), and it appears shorted to ground. I unplugged the sensor harness and verified I had 5v present on grey-brown.

While driving, I've thrown codes 22 (coolant sensor), 34 (speed control servo, I don't have cruise!), 35 (fan relay), and 54 (my distributor pickup is starting to cut out).

The temperature swings wildly, I think I baked the radiator cap and thermostat. I tested the radiator cap by using a home-made leakdown tester that very accurately regulates air pressure, and inserted my blow gun nozzle into the overflow hose from the radiator. The cap didn't hold any pressure at all; a replacement cap keeps me from overheating, but only if I run the heater full blast and drive below 55 on a cool day. You have to be really careful to regulate the air pressure, most air compressors won't be accurate and you could blow out a plastic tank or some other weak component with too high of a pressure.

I haven't confirmed the fan voltage yet, because the connector is stuck. I didn't see a barbed fitting, it looked like a friction fit. But I probably melted the relay, as the fan won't engage (even if I give it a push with a screwdriver) with engine running and AC on.

I found parts at www.autopartswarehouse.com, and it looks like they might have a factory compatible harness for a fan override (probably replacing the stock relay), which would be nice for cooling down if I ever get to test day at Bandimere in Golden, CO. I can get a replacement fan for 50 bucks.
 
#6 ·
If the fan was making noise before, probably the internals are now cooked and the bearing is locked up. The bearing probably locked up and this makes the fan stop spinning but the motor is still trying to push the fan and that draws a high current which then continues to cook the harness and the relay if left un-addressed/repaired. If the fan is just completely toast now, its not going to run period, no matter what you do. So the best way to test the circuit is going to be to disconnect the fan, put a test light across the fan wires and turn on the AC and the ignition. If the relay is doing its job, the light should come on and that will tell you the circuit and relay are good. If the fan was going bad and the circuit was allowed to get hot and stay hot for long periods of time, you need to check the connections at the bottom of the relay. They get cooked and the connectors will no longer make a good connection. They would in that case actually need to be cut off the wire cut also back to where it is still fresh copper and then new high-temp connectors crimped on. Do not use the commonly available aluminum or cheap-o thin metal steel ones. You want the heavy duty high temp ones that are available at most electrical counters and even real good hardware stores that actually have a good selection of hardware and bits and electrical pieces.

I am not a big fan of aftermarket auxiliary fans. Mostly because they do not include a shroud to increase air flow over the entire radiator core. The aftermarket fans typically only move air over the portion of the radiator that they cover. The shroud is important. Also note that your car came equipped with air fences that go behind the bumper cover and on each side of the radiator opening. They look like thick pieces of tar paper and they work to direct air flow into the radiator and not allow it to escape around it.

Bleeding the cooling system is also important on our cars. Do a search for how to bleed a 2.2 or 2.5 cooling system if you are not already familiar with this process. If not bled, the temp gauge will swing back and forth abruptly as the air pocket swishes past the temp sensor which is on the cylinder head over by cylinder #2, not where the thermostat housing is.

A radiator that is full of 50/50 mix, has ample air flow, is bled and that has a working water pump will keep the engine cool when cruising UNLESS the radiator is restricted and or clogged. The only other typical fault that makes a car run hot when its working hard is a radiator cap that is releasing pressure before it hits 16psi and a blown head gasket. Both of which are easy to determine...well most of the time. A blown head gasket can sometimes be a bit elusive to prove.
 
#9 ·
A satisfying conclusion:

I restored the stock fan setup by sourcing a stock Siemans fan from RockAuto (last one!) and replaced the fan relay. My mechanic was stumped until he found the blown fusible link. Taking the shroud off helped with the overheating, except when I got stuck in traffic. Of course I reinstalled the shroud once my mechanic had the fan mounted onto it.

Now it works like it should; fan comes on when AC is engaged, and kicks in around the middle of my temperature gauge when I'm idling in traffic, so no more overheating. I'm at 5'600 feet, so I wonder if the MAP reading tells the computer to kick in the fan earlier than sea level, due to the difference in boiling point.

I also had him replace a rear spindle that had molecularly welded onto the bearing when I didn't re-grease when it was squealing; there was a chunk missing from the bearing surface, so the wheel was a little loose. We also replaced a front axle because the boot was torn, and balanced the wheels. What a difference, the suspension has that nice stiff feel again and doesn't rumble above 65mph.

I'll post another thread, as the perfect storm hit and both my fuel pumps died while I was beating around without the fan. The inline went a long time ago, then the in-tank pump got flaky, and finally quit.
 
#10 ·
I single in-tank Walbro 190 or 255 is all the pump you will ever need. Forget, totally forget any other pump that you can get over the counter at the parts store or from RockAuto. Only a dealer pump, m a y b e an original Bosch over the counter, and the Walbro are known to work, last and be your friend. The aftermarket pumps, especially the ones made by Carter seem to just not hold up very well at all and quickly fail in a turbo car. Almost everyone that has gone that route has regretted it pretty quickly.

Walbro with the installation kit included from fwdperformance or turbosunleashed for the win.

If your hanger also needs to be replaced, then just FYI, you can get the hanger/sender assembly for an 88 Omni TBI car and use it in your 87 Charger or Omni no problemo. The 85-87 hanger/sender is the same but every parts counter of late will tell you no longer available typically.
 
#11 ·
Following up on my current problems...

The stock in-tank Bosch pump and hanger assembly went in without having to drop the tank. However, I seem to have a short because I get a close to zero ohm reading across the fuel pump fuse slot (12v to ground), and I think it must be caused by a short in the defunct external fuel pump. There is a spark when I attach the negative battery cable, but no spark if I pull the fuse.

I'm stubborn, and want to keep the stock configuration, although I will use a higher flow external pump. It looks like I can reuse the damper and side outlet attached to the stock Bosch pump (see drawing in factory manual attachment).

I scanned the manual page, and answered my own question, do I have to drop the fuel tank. The drawing shows the pump is above the fuel tank, doh! The manual says the internal pump has a check valve which regulates maximum fuel output, which might change my approach. I'll quote the manual, so it's easier for folks to copy this text for future reference.

begin quote

The fuel pump used in this system is a postive displacement, roller vane immersible pump with permanent magnet electic mtor. The fuel is drawn in through a filter sock and pushed through the electric motor to the outlet. The pump contains two check valves. One valve is used to relieve internal pump pressue and regulate maximum pump output. The other check valve located near the pump outlet, restricts fuel movement in either direction when the pump is not operational. Voltage to operate the pump is supplied through the Auto Shutdown Relay.

Shelby turbocharged models feature two electric fuel pumps. One pump is mounted in the fuel tank (Fig. 3). A second pump is mounted outside the tank (Fig. 2).

Multi-Point Fuel Injection system is under a constant pressure of approximately 380kPa (55psi). Before servicing the fuel tank, fuel pump, fuel lines, fuel filter, or fuel components of the fuel rail the fule pressure must be released. Perform fuel system pressure release procedure.

end quote

Since my car has been sitting for a few months and the external pump is shot, and I only started it once to move it, the fuel pressure had leaked down to where I could just depress the fuel rail schraeder valve and capture a small flow with a paper towel. I didn't want to pull an injector connector and hotwire the injector, flooding gas into a cylinder.

My question is will I be okay with an external pump that has extra output potential; the stock flow will be regulated to who knows what by the internal pump check valve as well as the fixed regulator on the fuel pump rail. Since I only have 15psi boost with the Mopar Performance computer, and had no issues with the original stock setup, I don't see any reason why this pump (rated to 340 LPH) wouldn't work for me.

Boosted Solutions 340 LPH Replaces Bosch 044 Electric Inline Fuel Pump #321880018703

The seller said this in response to my question "will it fit": "I have no idea what size pump was used to fit the OEM mount. These pumps are the same dimensions as the Bosch 044, but have more flow."

From the picture, it looks like the damper screws off the external pump along with the fuel pump right angle feed. Should be an easy swap.

I had asked my mechanic to replace the fuel filter when he did the inline pump, but it wasn't on his invoice. I never ordered the part for him to use. The filter looks old, and may be clogged, contributing to the fuel delivery problems I've been having. I think I changed it once when I first got the CSX from my brother 20 years and 50k miles ago.

All the hoses look original, and I'll replace with high pressure fuel line hoses.
 

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