Thermostat, heater, fan, temp questions...
 

I have a 92 Formula with the L98. I was using coolant, and it turned out to be a bad heater core. Got that replaced, but still noticed that the heater took a long time to warm up, and never did get as hot as it should. The ad where I bought the car from said it had an 160 degree thermostat, but the car was from Arizona, and Ive heard 160's dont work as well in a cold climate like Indiana. I replaced it with a stock part from Autozone that I assume is a 180 because when the temp gets to about 190-200 Ive noticed it drops back to 180. But my question is, despite all this it still takes far too long for the heater to warm up, and it doesnt get as hot as it should. Once the car warms up the temp runs in the 165-200 range, and the oil pressure is about 50-55, so thats ok. Before I did the thermostat swap there was a tiny puddle of coolant on top of the intake right beneath the therm housing. I drove it Sunday and it was dry, but after driving it to and from work today there were a few drips there again. I know about enough to be dangerous, but have a lot to learn. Oh, one more thing, the fans tend to stay on more than they should, if not all the time. Any clues?

Re: Thermostat, heater, fan, temp questions...
 

I believe stock thermostats were 195*F, and it might be stamped in the outer circular part of the thermostat itself. The stock replacement I bought from AutoZone was anyway. If you have coolant appearing near the thermostat housing, then that's probably leaking (especially if you used the paper gasket or didn't properly get all of the old one off). If you're using the stock gauge for those temps it's probably not that accurate. I would take that coolant neck back off and check the thermostat housing gasket/replace if necessary.

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I used a paper gasket with silicon sealant, maybe I didnt glop enough of it on there? The leak is very small, but I will look into it. Might need to tighten the bolts down just a bit more too. Any ideas on the fans or heater questions? Thx.

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They make a reusable O-ring style thermostat gasket. If you want to stick with the paper one, just make sure everything it's torqued evenly. Also, that gasket is thin once compressed, so even the slightest remnant of a remaining gasket can cause a leak.

How long does it take? What are your outside temps? It might be normal...
The fans? Are both of them running? Is there an aftermarket thermo switch for the secondary fan? Stock, those fans should only come on around 220*F and 240*F for primary and secondary respectively. Those fans being on won't help your heater warm up any faster.

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You may be right. i'll bet thats why its not heating up. The outside temp was about 20 this morning. It takes me about 20 min to get to work, and while it may be warm enough to make the car comfortable, it never gets hot (like "man turn that thing down") Anyway, I just went out and fired it up to check. Its been a couple hours since I drove it, so its cooled down some, if not all. The right hand fan was running right away when I started it. So just one. And btw, there is a drip or two of coolant on the top of the FRONT therm housing bolt. That sits above everything, so that didn't come from the gasket. Theres a little 3-4" long U-shaped hose above that, it may be the source of the leak because it sits directly above the front housing bolt.

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PS...if theres any aftermarket fan accessory, I don't know it. I don't think there is. Could it be the computer? One guy that was helping me with it said he got some funny readings from the comp when he hooked it up. He said it kept acting confused about what gear it was in, and was tough to get readings from. He said its possible when the heater core busted some coolant got into the unit. But otherwise it seems to run fine, so IDK.

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You can change the PROM to allow the fan to come on earlier, but that's just the primary I believe. The secondary fan should be controlled via a thermo switch in the passenger side head. I replaced mine with an after market one that comes on earlier ~190*F before I got into burning new PROMs. I guess if somethings up with your ECM, you could always replace it and see, but I wouldn't worry about it unless something serious happens.

That U-shaped hose could definitely be leaking. Check for cracking or the clamps cutting into it. Also, check to make sure those clamps are tight. It also might be the upper radiator hose leaking down onto it.

On a side note, you can unplug the relay ground for the secondary fan at the thermo switch (regardless of whether it's aftermarket or not) and just not use it. If it's cold outside, your primary fan will be plenty, and come on later (assuming 'right' means passenger side)

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Yes, the passenger side fan. The relay is on the head you say? Is it hard to get to? What does it look like? Thanks for your patience, a lot of this Im just learning. But still, what is actually wrong that its coming on so soon?

Re: Thermostat, heater, fan, temp questions...
 

How hot are the hoses running to / from heater core ?

Re: Thermostat, heater, fan, temp questions...
 

it is difficult to get to. If you can see the temp sending unit in the driver side head, it's in the same spot, one cylinder further back...if that makes sense. You should see a thin wire coming from the wiring loom that goes down to the starter IIRC. Unplug that and no secondary fan. I had to get underneath the car to change it. It's easier to unplug it as well from underneath.

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Haven't checked the heater core hose temps yet so I don't know.....

Re: Thermostat, heater, fan, temp questions...
 

Ok. I'll have to get in there and look. Ive noticed about anything on the passenger side of that motor is tough to deal with. God forbid I need to change a valve cover gasket or something. Maybe the sending unit needs to be replaced, and thats why the fan is coming on. Looks like its 12.99 at autozone. Might be worth a shot....thanks for your help. If theres anything else you want to add in, feel free--Im a bit of an ignoramus--a LOT to learn!

Re: Thermostat, heater, fan, temp questions...
 

I know that neither of the fans should be on right after starting, let alone all the time. I haven't looked at a wiring diagram but if it's controlled by a relay, my money is on it being stuck in the closed position. It's not that uncommon, especially with older vehicles.

Re: Thermostat, heater, fan, temp questions...
 

Ok, but how do I fix that? I thought maybe the sending unit was bad too.

Re: Thermostat, heater, fan, temp questions...
 

The temp sending unit is only for the gauge, as the ECM uses the CTS for necessary coolant temp dependent parameters. Just FYI. I wouldn't replace that thing unless your gauge isn't working or way off. I replaced mine and it still isn't accurate. From what I've read, you have to clean a bunch of contacts in the printed circuit and other ground contacts behind the inst. cluster...

If you're serious about your car and planning on keeping it, I would spend the money to get some PROM burning and datalogging equipment. You can adjust the fan temp, enable highway mode (which WILL save you some gas mileage), and tune your car to run excellent. It also helps by showing faulty sensors, certain errors within the ECM, and help with things like this as you can monitor temps and such while driving. Downside: your wallet will be ~$300 lighter...

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No, the gauge is fine as far as I know. But if the fan is on because of a bad relay switch, where is the switch? But now Im confused. I thought the sending unit controlled when the fans come on? If not, why does it connect to the fan? Or does it not connect on an L98? Getting prom burning and datalogging is great, and Id love to get into it when I get more money, but it doesnt help me figure out why the passenger side fan comes on as soon as you start the car. I am a novice at this, a lot of that stuff you're talking about is over my head. What do I need to fix/replace to get my fan to behave correctly?

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I highly advocate everyone getting in to prom burning but you can't just program it out, if there is an issue with the control curcuit of the fans it needs to be fixed physically. I could get some diagrams and locations tomorrow from alldata or Mitchell at school but that's the best I could do. I'm not one to just throw parts at a problem but relays are so cheap it probably wouldn't hurt to replace it. If you were really gonna test it you'd need a DVOM or voltmeter available. To test a 4 pin relay for being stuck in the closed position you would need to unplug it and measure resistance between pins 30 and 87, If you get anything other than OFL or out of range (meaning super high resistance or no continuity) then its closed. If it's a 5 pin relay that's another story, you's need a wiring diagram.

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A relay is an electrically controlled switch. Usually just looks like a 1 inch by 1.5 inch black box with four or five pins on one side. It has a coil and switch inside of it. A controlling device sends power through it's internal coil which pulls the internal switch closed but occasionally these switches can be stuck closed. Now, of course this is a shot in the dark because, once again, I have no knowledge on how thee fans are controlled on these particular cars. I know relays are common in this application and it very well could be causing your symptom.

Re: Thermostat, heater, fan, temp questions...
 

In this thread is a wiring diagram for your coolant fan system
https://www.thirdgen.org/forums/cool...-replaced.html

Re: Thermostat, heater, fan, temp questions...
 

Ok, first things first:
Temp sending unit--->Coolant temp gauge

Thermo switch in head---> grounds the control circuit for the relay, thus turning on the fan.

If the relay is stuck shut, it means the control circuit doesn't need to be energized to power the fan. This should help http://www.mp3car.com/the-faq-empori...ire-it-up.html

Fans should be 4 pin relays

Quick question: when you first start your car, does the fan immediately come on?

Re: Thermostat, heater, fan, temp questions...
 

I see that it is controlled by a relay, To test or swap it out is only a matter of finding it. lol

Re: Thermostat, heater, fan, temp questions...
 

My bad, I was looking at the diagram and noticed that the power supplied to the relay is "hot at all times" so if a stuck relay was your culprit, it would run even when the vehicle is off.

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Ok thanks. According to the autozone site, my fan relay shows five prongs, and is only $10. Might be worth replacing. I would love to get into PROM and datalogging. I had a problem with the ignition on my 98 Camaro that made the car sound like it was shaking to pieces, but was really simple to fix. It only showed up on a program like that. A guy I know rode in it with the computer on it til it did its thing, and he caught a misfire that the dealership didint even catch.

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From this diagram I've supplied, It looks like the only input the PCM gets to control the coolant fans is the coolant temp sensor. If the temp sensor is internally shorted (bad), it would tell the PCM that the coolant is at a ridiculously high temp all the time, which would turn the coolant fans on regardless of the actual temp.

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Haha, man you gotta be kidding me. I have no idea how to read that. My Haynes manual has stuff like that, and I have no clue what it means.

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Yeah, the passenger side fan comes on as soon as you start it. The drivers side fan was off. Autozone shows a 5 pin relay for my car. IDK

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Ok. Sounds about right. Where is it on the car?

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Ok. i have this same diagram in my haynes manual, let me give it a look....

Re: Thermostat, heater, fan, temp questions...
 

I'm assuming it's right around the thermostat housing. Should be a two wire sensor screwed into the housing, intake or block.

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Does the fan come on with the key on engine off?

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....looked at it and it still doesnt make sense. I HATE wiring.....

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No, only when you start the motor.

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The manual shows the temp sending unit screwed into the block near the therm. There is one on each head. It never mentions a temp "sensor".

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If your able to mess with it now, and can find the sensor, I'd unplug it while it's running and see if that stops the fans, sort of a poor mans test. If you unplug it the PCM will read that as -40 degrees. It may not like you doing that very much but won't hurt anything.

Re: Thermostat, heater, fan, temp questions...
 

Hmm, well, The temp "sender" probably doesn't have anything to do with your issue. It just tells the gauges, it shouldn't control the fans. You have two coolant sensors?

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Ok. I cant do it now, but will asap. If it needs to be replaced its only $12. One more question: which fan is the primary? The passenger side fan is the one running at startup, is that the secondary fan or primary?

Re: Thermostat, heater, fan, temp questions...
 

Maybe the diagram I found isn't for your particular engine/car combination

Re: Thermostat, heater, fan, temp questions...
 

I have no idea, like I said, I don't know every specific setup on different cars, I look it up when I can. lol

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Idk, Ive not looked at this before, Im just going by what the book said. Tonight is the first Ive even learned about all this. There is no mention of a temp sensor in the book, only a sending unit.

Re: Thermostat, heater, fan, temp questions...
 

Well, its in the haynes manual for my car. Theres a page for 5.0 and one for 5.7. Mine is 5.7.

Re: Thermostat, heater, fan, temp questions...
 

I'll look it up tomorrow and post it here. If you still have the issue it might help. If you've fixed it maybe it'll help someone else. lol Your talking about your 92 TPI firebird, right?

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Yip, 92 5.7 tpi. Thanks for all your time and help. I'll be looking out for what you post. I wont have it fixed by tomorrow. We'll be freezing our butts off, plus I have to work. LOL

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Anyway you could take a picture and post it here?

Re: Thermostat, heater, fan, temp questions...
 

A picture of what? The motor? A sending unit?

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Btw, because of this extended conversation, Ive now gone from junior member to member. Bwah hahahaha...thanks...lol

Re: Thermostat, heater, fan, temp questions...
 

Fyi.....the diagram in my manual does show a temp sensor, but I havent seen mention of it in the text of the book itself, it only mentions temp sending.

Re: Thermostat, heater, fan, temp questions...
 

https://www.thirdgen.org/forums/tpi/...old-start.html
CTS is the one circled. You don't have the switch to the left of it. You only have one of those. In the heads are the temp sending unit (for the gauge) and the thermo fan switch (grounding out the relay for the fan). The relay should be located on the firewall, driver side, near the hood hinge. There should be 3 of them, with two of them being fans IIRC. Check the larger wire colors and verify with the wires powering the fans. The other relay is the fuel pump: https://www.thirdgen.org/forums/elec...-3-relays.html

Re: Thermostat, heater, fan, temp questions...
 

Ok. Thx, will check it out asap. Thanks again!

Re: Thermostat, heater, fan, temp questions...
 

..yes, thats it! That looks just like the relay switch I saw on autozone's site, and the cts will be easy to find. This is the best way for me to learn this crap. I like to be able to actually SEE what Im dealing with.