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1987 2L High Norm Temp


VetteNZman

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Hello, ‘87 2.0L temp gauge is staying at a high normal on interstate driving (30miles, 60F). For a while temp appeared stable at mid NORM. Since I completed a years worth of slow work on my ranger the temp gauge shows high. I run heat high to try to mitigate. I think temp should be between letters O and R of NORM. Sending unit replaced 2 years ago and water pump / thermostat / cap replaced maybe 4 years ago. Temp never goes out of NORM range. Fan, leak, cap, sender.....???
 


RonD

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If its the fan(clutch) then temp goes up when stopped or driving slow, then goes down at faster speed

If temp climbs at faster speeds then either thermostat is not opening fully or radiator is getting clogged up

Simple test for this, start cold engine, feel upper radiator hose and heater hose, they should, of course, both be cold, lol
Let engine idle a bit and then feel them again, upper rad hose should still be cold, heater hose should be warming up
After 5 to 8 minutes the heater hose should be HOT(150degF), and upper rad hose cold or just starting to warm up, as thermostat opens

If upper Rad hose is warming like heater hose then thermostat is stuck open, usually 1/4-1/2 way so it can't open fully

If thermostat seems to be working then check radiator, after full warm up, i.e. when you get home from a drive, shut off engine
Unbolt the fan shroud and pull it back over the fan
Run your hand over radiator fins, should be warmer at the top and then get cooler towards the bottom, NOT cold
If you feel cooler spots/areas those are blocked passages
Whole area should have nice even heat that gets 15deg cooler at the bottom
So coolant goes into the top of the radiator at 190deg then comes out at the bottom at 175deg

You can pull radiator and do "flip test"
Stand radiator on its side, either side so tubes are going up and down, with rad cap on
Put hand over which ever is lower rad hose port and fill rad with water using the other port
Stop filling when full

Remove hand and radiator should drain very fast, now the flip test
Flip radiator upside down.............NO water should come out, rad should be empty, if water does come out it could only come from BLOCKED TUBES inside

You can try flushing, lay radiator on its back and fill it with warm water with CLR mixed in, let it sit for 15-20min then flush, repeat a few times, then do Flip Test again



The "letters" on the temp gauge are different in different years, so best to use 1/4, 1/3, 1/2, ect...............for needle points

Ford gauges usually have 210degF as 1/2, engine should run at about 190degF when fully warmed up, so just under 1/2

The 2.0l/2.3l has the temp sender at the rear drivers side of the engine so tends to show lower temp on the gauge just above 1/3 usually


Water pump impellers(fins) can be eaten away if coolant gets too old, from galvanic corrosion or electrolysis, this reduces the flow of coolant, very rare occurrence, but not unheard of
 

VetteNZman

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Ron, thanks so much for the comprehensive guide. Here's what I found Sat. on cold startup. Temp rise on the heater and top rad lines looked ok, however, while I was looking at them I noticed a small drip and puddle below the left lower corner of the radiator. So at this time I'm assuming I have a small leak in the radiator. I do not recall having to add any coolant in recent memory. I was think with a leak in the system, the temp would not even stabilize at a high normal but this leak does not seem to drip visibly at all times and I guess it could change with core temp / pressure.
 

RonD

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The pressure in the cooling system comes from the properties of liquids, liquids expand when heated, so as engine heats up coolant it expands in volume, this creates pressure inside the cooling system

Rad cap is usually rated for 14psi pressure, at 15psi it is pushed open and sends some hot coolant over to the overflow tank, until pressure drops to 14psi again
Most overflow tanks have a COLD and WARM line for this reason, level should change during warm up and cool down

On cool down, engine off, the pressure drops down to 0psi as engine gets cold again, if any coolant was sent over to Overflow tank then pressure will drop to -1psi
There is a smaller valve in the center of radiator cap, this valve will be Sucked open by the -1psi pressure and coolant in the Overflow tank will be sucked back in to keep coolant "topped up" in radiator, so coolant should be back at the COLD line on overflow tank, if its BELOW COLD line then you have lost some coolant during heat up and cool down

Yes, some leaks are small enough to only leak when cooling system has pressure
 

VetteNZman

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Update on this - not clear that a possible small radiator leak was the temp issue either since I've now replace the radiator.
I was reading on a Mustang site where folks there claim if you do not get the correct Motorcraft sender, the gauge will likely never read correct. Some noted they have NEVER used a non OEM sender with success. The sender on the truck was replaced non OEM over a year ago but just before I starting some restorations which took most of a year so there was minimal driving with this sender in place. Going to drive it 50 miles tomorrow and see what happens.
 

Bird76Mojo

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There are a few different senders available. They usually have different colored rings on the top of them, which Ford/Chevy/Chrysler might have meant to be used as color coding originally. The worst part is that depending on manufacturers, the different coloring of the rings isn't held to any industry standard, so you never know what you're getting depending on which brand you buy. The different colors don't seem to indicate anything as far as which ohm level sensor you're getting. I have seen oem Motorcraft senders on Ebay lately that were New Old Stock, so you might go that route.

On my V8 swap in my 87 Ranger, I had to buy two different senders to see where it would make the gauge ride, and then verify that my coolant temperature was within acceptable limits by checking temps at various places on the radiator body, radiator hoses, etc, with a point-n-shoot thermometer.

If you know someone with a kit to test radiator caps, then I'd also test the new cap you bought to see if it's maintaining the proper psi without any leakage.
 

VetteNZman

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Looks like things are ok after the 50 mile drive test on the new radiator. Point and shoot temp checker was at about 195 to 200F. Gauge at mid range.
 

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