91 VR4 overheating issue... kooky ...

[dudewith91vr4]

Never assume anything Check it, rule it out.

You should be able to get to the sensors if you unbolt the engine bay fuse box and remove the overflow bottle, you might even have to remove the front pre-turbo intake pipe. The sensors are on the RH bottom corner of the radiator lower tank, you might have a hard time unplugging them though since you can't actually see them.

Get to them from underneath if you can. You might not have to completely remove the tray, you could possibly just drop the back of it down a bit and get in behind it.

where is fusible link #5 on this beast ... can't find it in shop manual

[dudewith91vr4]

making progress in my goofy way... replaced coolant temp sensor to ecu (because it was easy and cheap)... now I have heat for some goofy reason! Maybe it let some air out of the system and regained circulation...

Jumped the low radiator fan relay connections with vehicle temp above halfway mark (ignition ON), no dice, passenger side fan was dead. Jumped the same fan relay connections for low radiator fan relay (with the ignition OFF) and the heater came on, and the passenger side fan was working, super low speed. By the way, both work when the a/c is on. If I jump the high radiator fan relay, the passenger side fan comes to life, in high beast mode.

awaiting instructions to proceed... sir ...

[box]

The fusible links are the plastic topped main fuses in that same fuse box.


Have you checked any fuses? The 40A one is for the radiator fans

Ignition on or off shouldn't make any difference when bypassing the relay, neither should coolant temperature. Just to confirm, here is a pin diagram of the relays (forget about pin 87a, our relays don't have this)


You're bridging pin 30 and 87 right?

Anyway, have you got a test light? Or a multimeter?

Here's a section of the wiring diagram for the low speed fan.
[img][/img]

You want to check your voltage at the low speed fan relay. Pin 30 should have 12v if the fuse and fan motor is OK, pin 87 should have 0v (or it could be the other way around).

Does it still overheat with the a/c on? If it does, something else is causing your issues.

[dudewith91vr4]

The fusible links are the plastic topped main fuses in that same fuse box.


Have you checked any fuses? The 40A one is for the radiator fans

Ignition on or off shouldn't make any difference when bypassing the relay, neither should coolant temperature. Just to confirm, here is a pin diagram of the relays (forget about pin 87a, our relays don't have this)


You're bridging pin 30 and 87 right?

Anyway, have you got a test light? Or a multimeter?

Here's a section of the wiring diagram for the low speed fan.
[img][/img]

You want to check your voltage at the low speed fan relay. Pin 30 should have 12v if the fuse and fan motor is OK, pin 87 should have 0v (or it could be the other way around).

Does it still overheat with the a/c on? If it does, something else is causing your issues.

checked low speed fan relay with digital multimeter... pin 30 has 12.7v, pin 87 has 0v. checked all fuses with a test lamp, also checked (for continuity) and swapped fusible links to make sure they work. Will run vehicle with A/C on to see if it overheats. I will remove the front aero to gain access to the radiator and drain it, see what comes out, i might just order a new one, then i'll check the fan switches and wiring. thanks again, will report back ...

[Ange]

maybe you're water is clogged somewhere. wouldn't hurt to do a flush

[dudewith91vr4]

maybe you're water is clogged somewhere. wouldn't hurt to do a flush

ange, that's definitely a possibility, what's a good price to pay for that? i can't do it at my house.

box, ran the motor with a/c on, initially, both fans came on, eventually, only the driver side fan stayed on (in what seemed like high speed), not sure. the vehicle stayed much cooler, until i raced the engine about 4 times, then it made its gradual climb to about 3 clicks short of the red, so i turned the motor off. Again, it has a small hose leaking on the right lower half of the thermostat housing. it's not pushing coolant now, but i haven't taken it for a drive. next move?

[box]

Check the resistance from pin 87 to ground.

If it's overheating with the a/c and fans on, it's a mechanical problem. Fix the leak at the thermostat housing first and then monitor whether the engine is using coolant or not.

[dudewith91vr4]

Check the resistance from pin 87 to ground.

If it's overheating with the a/c and fans on, it's a mechanical problem. Fix the leak at the thermostat housing first and then monitor whether the engine is using coolant or not.

ok box, thanks... finally took the front aero off, piece of cake. unplugged sensors screwed into the bottom passenger side of the radiator, jumped the wires on black connector and both fans went on, jumped wires on white connector and the relay clicked, but the passenger side fan didn't turn on... replace the fan? ... going to drain and flush the radiator now, see what comes out.

[box]

replace the fan?

No.....

Check the resistance from pin 87 to ground.

Do that. It should be going from 87 to ground via the low speed fan resistor as shown in the diagram above.

[Ange]

ange, that's definitely a possibility, what's a good price to pay for that? i can't do it at my house.

box, ran the motor with a/c on, initially, both fans came on, eventually, only the driver side fan stayed on (in what seemed like high speed), not sure. the vehicle stayed much cooler, until i raced the engine about 4 times, then it made its gradual climb to about 3 clicks short of the red, so i turned the motor off. Again, it has a small hose leaking on the right lower half of the thermostat housing. it's not pushing coolant now, but i haven't taken it for a drive. next move?

it's easy to do by yourself if you have access to a regular water hose. you just need a t-fitting and a hose that fits the waterfitting that goes from the firewall. there is kits you can but also.