Overheating due to fan not working

[Seamus68]

Car: 84 Rabbit 16v CIS-e

I have just done an overhaul on my rabbit's cooling system. New Parts:
Radiator
Fan Switch (standard temp)
Water Pump
T-stat (standard temp)

My problem is the fan will not turning on, I let the car run for a while yesterday after filling back up with coolant to burp the system. The fan WILL run if i unplug the connector at the thermo sensor and jump the two prongs. But while running the car it can get to the last white line before the red "danger zone" of the temp gauge and the fan will still not kick on.

Oh also it took a little while, but the lower Rad hose did become hot which tells me the t-stat is operational.


Could I possibly be missing something, any help would be appreciated. Thank you.

[wilm13]

Bad switch? Just because something is brand new does not mean it works as I found out recently with a BNIB reverse switch. Too 'hot' of switch? What year rabbit.

[Eastep]

Id check for air in the system JIC, and get a new fan switch. You'll be good after that

[Seamus68]

Bad switch? Just because something is brand new does not mean it works as I found out recently with a BNIB reverse switch. Too 'hot' of switch? What year rabbit.

It's a possibility. I may need to put it in some hot water and use a multi-meter to test the switch.


it's an 84.


Also, short of running the car with the cap off the overflow tank, how else can one remove possible air in the system? Also I did fill the car with coolant from top rad hose to insure as little air as possible before topping off at the tank.

[R32peterb]

I had the same problem, then I noticed the prongs on the thermostat were a little bent. after straightening them my fan started working, guess they were just not making a conection when they were bent.

[chrissev2]

if the fan won't turn on it may be because there's air in the system and no coolant in the rad. You can let it out by as you stated cracking off the rad cap a bit, but don't do that when it's hot (system is pressurized when hot). Usually if you fill from the top hose into the motor with the rad cap off, that bleeds most air out. You can't fill into the rad as the thermostat is closed and coolant will not get to the motor. Any remaining air can be bled out by running the motor until it becomes warmish and then, while wearing gloves and face and body protection of some sort, slowly releasing the rad cap just slightly to let out the air. Don't release the cap too much or coolant will spray everywhere and don't do this unless you are covered up as you could be quite badly burned.

If fan is still not turning on check your wiring for continuity and check your temp switch by putting it in hot water and checking for continuity over the leads when the hot water is at the specified temperature.

Chris

[JUS_GT_EYEZ]

if you can jump the harness you prove that the wiring is good. the only thing left is the switch, the radiator and air in the system.

the easiest thing to test is the switch the way you mentioned.. you will need a thermometer to make verify what temp it actually opens at.

have you checked to make sure your lower hose is getting hot? the radiator could be clogged not just airlocked.

[Seamus68]

if you can jump the harness you prove that the wiring is good. the only thing left is the switch, the radiator and air in the system.

the easiest thing to test is the switch the way you mentioned.. you will need a thermometer to make verify what temp it actually opens at.

have you checked to make sure your lower hose is getting hot? the radiator could be clogged not just airlocked.

Checked the switch last night in a pot of hot H20. Using a multi-meter the switch closed and I got continuity at ~200* (using a candy thermometer to measure water temp).

So that leads me to believe I have air in the system. So going back to the garage this evening and see what i can do about purging the system.

I will report back with the conclusion to this tale.

[JUS_GT_EYEZ]

i have had luck with massaging the upper radiator hose with the cap off while its getting warm. basically just squeeze the hose while the coolant is flowing thru it and let air escape back toward the open bottle.

[Seamus68]

i have had luck with massaging the upper radiator hose with the cap off while its getting warm. basically just squeeze the hose while the coolant is flowing thru it and let air escape back toward the open bottle.

Thanks Ivan!

[WackyWabbitRacer]

The later models of MK1 had an additional relay in the radiator fan motor circuit.

If this relay is not working properly, the radiator fan will not run.

Cheers, WWR.

[rabbitnothopper]

backorder

321919505

[benjaminobscene]

i have had luck with massaging the upper radiator hose with the cap off while its getting warm. basically just squeeze the hose while the coolant is flowing thru it and let air escape back toward the open bottle.

This has always worked for me when bleeding an ABA cooling system. The idea is by squeezing the upper hose you're causing small pressure changes in the system that help the air bubbles up to the reservoir. You can further stir things up by revving the engine and then squeezing. Be careful though, because if the coolant gets too hot it will expand rapidly and boil out of the reservoir.

[Seamus68]

Gentlemen, i thank you all for your input and help. The fan and whole cooling is fully operational. Ran the car for quite some time massaging to upper hose getting air out. Temp gauge still climbed and no fan. I decided to go to get a meat thermometer at the store and put that in my res while running the car a second time (just in case my gauge was wildly off for one reason or another). During that time i still massaged the upper hose, and low and behold...BOOM...fan turns on. And all is well. It just had too much air in that system needing to be expelled.

[JUS_GT_EYEZ]

[benjaminobscene]

bitchin! I'll see you (+car) at the halloween gtg then!

[Seamus68]

Yes sir! see you there!

[waabooz]

My caddy was doing the same thing. I parked it for a month and drove the other rabbit. When I got back to the caddy it had fixed itself. I'm really pleased to know why now. thanks.

[JUS_GT_EYEZ]

another method is to drive it around the block a few times as it warms up. the bumps and turns seem to help alot. maybe its just how i drive tho.

[WackyWabbitRacer]

To minimize air in the cooling system, fill the engine block via the top radiator hose until the hose overflows. Quickly reconnect hose to the radiator and check the coolant level in the radiator.

If the level in the radiator is low, then add coolant to the "cold fill mark" on the radiator.

Cheers, WWR.

[rabbitnothopper]

good notes:

air in coolant system cannot be read by fan switch