Temperature spikes, does this sound like air?

[Techno Duck]

Just changed the headgasket, block and radiator were completley drained. I filled up the block through the top of the cylinder head when i still had the upper coolant neck off the car. I then filled up the expansion tank until i had water coming out of the high point vent. Turned the car on.. full heat and let it run and opened the vent again, got a steady stream of coolant. All seemed well so far.

I drove the car over 150 miles yesterday as a shakedown. Runs great on the highway and even around town. Temps never go much higher than the first white line on my dash gauge and my aftermarket gauge dosent read higher than 190-200 degrees. The aftermarket gauge is reading off the upper radiator hose.

However when i come to a stop and let the car idle for maybe 30-60 seconds, the temperature steadily raises up to about 210 degrees on my aftermarket gauge. I dont trust the dash gauge as it only reads about halfway, once it went up to just under the 2nd white line. I think the dash gauge is off by about 10-15 degrees when comparing to my after market.

I am just wondering if this sounds like i have air in the system or not. I am not loosing coolant nor does the car overheat. It just seems to run a bit hotter than it used to before the headgasket fiasco. Fans still come on also.

Going to try and bleed it more this weekend. Any other reasons this would be happening?

I came across this nice diagram that shows the actual temperature with the dash gauge...



and for us Americans, i converted the 'C to 'F.



BTW, has anyone wired a LED or light to come on when the fans kick on? Any idea how i can do this? I am not very electrical savy...thats why i am a mechanical engineer .

[many944s]

Hey duck...
Wiring a LED to the fans is not that hard, in fact I did the exact same thing on my '85 944. I used 2 reed relays available at any RadioShack. It requires some splicing of the fan harneses, but basically the relay is set up so that 2 of the leads are the "feed". When current runs through the harness (and relay) to turn on the fans, it creates a small magnetic field in the relay closing a small magnetic switch thus activating the second pair of leads or "output" leads. One lead of the "output" of the relay is run to the positive "+" of the battery, the other to the LED. The negative lead of the LED is then run to any available ground. I have LEDS for each fan on my dash which only requires 2 wires to be run through the firewall. It is then very easy to determine which fan is running. If you need more detailed instructions, just ask and I will send photos and a step by step procedure for you.

Good luck!
Nick

[Techno Duck]

Nick, i would much appreciate a step by step procedure with where i need to splice into the fan relay harness.


I am thinking maybe im just being a bit paranoid. The fans kick on when the dash gauge gets to the halfway mark roughly. Now my aftermarket gauge temp goes up steadily to about 210 degrees F as the dash gauge works its way back down to the first white line. Does it sound right that the coolant leaving the cylinder head (and going through the upper radiator hose) is at about 210 degrees?

[pozican]

I've seen my turbo do that.

It'll go up pretty far on the stock temp gauge, but I never worried about it because if I moved about a foot or two it would go back down...

[many944s]

I will have to crunch some numbers, but the fans usually kick in when the factory dash temp guage is at the half way mark. As soon as the wife gets home and can watch the baby, I will run out to the garage and take some pictures of my splice locations. I will also draw up some scematics and scan them in as a .jpg so I can post it here.

-Nick

[Techno Duck]

Thanks Nick, its much appreciated. I am not totally dumb electrical wise as in i can splice wires (ive wired two radios for my cars now) but figuring out where to splice and how to wire to get 12v is a bit iffy. I got lucky when i hooked up my aftermarket gauges .

I just ordered a new thermostat and fan switch to play it safe. I am really wondering though what temperatures you guys see at the upper radiator hose. 210 'F sounds normal i guess.. its just weird to see the gauge go that far over..i dont think its ever done that before.

From what i understand for late model cars.. the low speed fans should kick on at 92 'C and the high speed kick on at 102 'C. That is with the OEM type fan switch. The thermostat opens at 83 'C, again this is the OEM thermostat.

So you are right.. the fans should kick on at roughly the middle area for the dash gauge.

[Techno Duck]

Can anyone test something for me quickly... put the ignition key on the 'on' position but dont start the car. Press the a/c button, do the radiator fans turn on still?

My a/c dosent kick on even when the car is on.. i was attributing that due to the low refrigerant level (the low pressure cutout for the compressor). Are the fans supposed to turn on regardless?

[many944s]

Here is the schematic for splicing in the relay and LED setup. Make sure you use LEDs with internal resistors so you don't burn them out as soon as the relays close.



On my 944, I have a large breakout block on the positive terminal of my battery. I originally installed it for large power leads to my amplifiers, but it also has 4 smaller terminals that I snatched power off of for these fan LEDs. This can also be accomplished with a medium ring lug attached under the clamp bolt on the battery terminal.

I didn't get a chance to take any pictures of my setup, but the splices I made are about an inch from where the factory connector attaches to each fan. I simply split the outer insulation and cut the power supply wire (not the ground) then connected the relay in line. One wire can be run from the positive terminal of the battery to the location of your two relays, then connect them in parallel (for the switched side of the relays to provide power to the LEDs when closed). From here you only need to run two wires through the firewall to the location of your LEDs (one for each fan/relay/LED combo. The Negative side of the LEDs can be grounded anywhere you'd like.

Enjoy!
-Nick

[Techno Duck]

Nick, excellent write up. I will probably get the parts this weekend and tackle this in a week or two. I can vision mostly everything but would appreciate just a picture of the connections at the relay. Can you use a standard automotive relay?

Any chance you remember the part # for the relay at RadioShack? Again.. this is where my electrical knowledge goes out the door .

Ill finally have a usage for some of the switch blanks on my center console now.. .

Is this the right type of LED you were talking about?

http://www.radioshack.com/product/index.jsp?productId=2062561&cp=2032058&f=Taxonomy%2FRSK%2F2032058&categoryId=2032058&kwCatId=2032058&kw=led&parentPage=search

Again, please forgive my ignorance in this area.

[speedracing944]

At work we used these current sensors which were wired to LEDs. The current sensors did not have to be spliced, they had a black platic loop that the wire got thread through. The sensor sensed the magnetic field created by the current and then lit up the LED. It was pretty cool.

Speedy

[Techno Duck]

Another update. The low speed fans defenetley work. Fans were running and i shut the car off, fans continued to run and turned off after a few seconds. I turned the key to 'on' which should have triggered the highspeed fans and they didnt change speed. It is possible it was just below the high speed fan switch temp though.

So i am now thinking its possible the high speed fans are not working correctly. Im lucky its only about 50 degrees out so the car hasnt even come close to over heating yet, even in traffic. Going to test the relay this weekend.

Still wondering if the high speed fans turn on with the a/c on a car with low refrigerant. I think they are supposed to. Probably my relay that is messed up..

[Razorback1980]

I'm not really sure where the fan switch picks it's power up from but I'm guessing the fans should work the same no matter the refrigerant level.

[many944s]

Jon,
Thanks for the compliment!

I just checked both my '83 944 and '85 944, the high speed fan DOES run when the car is in the "on" position without the car started and A/C turned to "on". I also jumpered the pressure switch for the A/C charge to see if it would happen when the DME thinks there is a "low charge". The fan will still run with a low charge.

As for the part number:
Radio Shack stock# 275-233
Single pole/ single throw magnetic reed relay looks like this:


As I recall, there should be a basic diagram on the back of the packaging that will help with install as per the schem. I posted before.

If you need help on installing feel free to call me (765)418-6794

Laters,
Nick

[Techno Duck]

Thats for the info everyone. I have a good feeling then its the high speed fan which is not working then. I will have to jump the connector at the fan swtich to verify this weekend. Looks like ill have to open that relay up before i drop the money on a new one.

Nick, thanks again for the help. Did that LED which i linked to look like the right type? It says its 12v capable, but it dosent have the resistor.

[many944s]

Yup, that one will work just fine. I used a couple of blue LEDs that I picked up from a supply house, but any LED will work as long as it is rated for 12v.

Good luck!

-Nick