temp needle goes straight past H

[mikeinaus]

i was messing around with my gauges last night to fix my clock and when i put it all back together i noticed my temp needle wasnt working. i took it apart again this morning and noticed i forgot to put in 2 of the screws in the back of the cluster for the temp needle. i put them back in and started my car. within 1min it was at h. i turned the car off and felt the engine by hand and opened the coolant fill neck. the engine was cold and the coolant fill tube was a little low. i filled it back up and started the car again. after a few seconds the needle went past h and to its farthest point. i took the cluster apart again thinking i installed the temp needle backwards but it was correct. tried putting it back into the old cluster and it still goes straight to the roof. if i unplug the dash temp sensor in the engine the needle goes back down.

is it possible i messed up the motor on the temp needle by not screwing in the 2 screws? could my temp sensor have magically fried on the 10min drive i went on after i had it all together?

another random question. i check my coolant fill cap randomly and sometimes its low so i fill it up. when i come back and look a couple of days later my resevior has more coolant in it and the fill hose is low again. is this normal? when i first did my engine swap my water pump was leaking steam a bit but i havnt noticed it for quite a while. why would my coolant level drop without going into my resevior?

[SpatialTerror]

well i dont know what to tell you bout your temp gauge.
but you got a bad water pump. thats why your losing coolent.
and with the water pump bad it might not be circulating water right. causing your water temp to skyrocket.
even if you have a decent size air bubble in your coolent lines can scew with the circulation.

fill your coolent full.
start your car and let it warm up
feel your coolent return line.
if its hot and feels like waters rushing though it.
you have circulation.
and REPLACE YOUR WATER PUMP!!!
i cant stress that enough.
your just wearing your motor down faster with the water pump like it is.

[Ryan]

Its normal that the fill cap is sometimes low. The coolant expands/contracts on heating/cooling. Thats the only reason we have overflow tanks.

If you waterpump is leaking, get it replaced. If it only did it for a moment, thats still bad, but make sure its the waterpump! I had a leaky fuel line, and that was much scarier than a waterpump issue. (Was using a Ford BP rail, so the low pressure side was on the pass side)

[mikeinaus]

gas needle and temp needle are to the roof now. think i may have a short in the wires in the back somewhere im gonna check that out.

[Newfie_dan]

coolant and gas gauges are resistance based sensors, if they raise to the max then the resistance is either way to high or way to low, in the case of the temp sensor its low resistance that makes it run up to the highest point. Measure the resistance on that single wire coolant sensor when its hot and when its cold it should be different. As for the gas gauge check out the wiring to the fuel pump look for corrosion in that plug or a place where the wiring could have gotten damaged. FYI the printed cicruit board on the back of the cluster may have gotten damaged so check that out as well if you have it out.

[mikeinaus]

i compared the circuit boards on both the clusters. the new one seems to have the power for the clock go threw a few of the light bulbs. im thinking one of the bulbs was dead and caused a short, cutting off power to the clock. the old one had a dedicated circuit for the clock so it didnt have the problem. it just doesnt make sense to me how they could both (sensors/harness) get fucked up at the same time when i was messing around with the clusters.

since there resistance based and low resistance = high temp/ full tank im thinking the plug itself might not be making very good contact with the board. ill try cleaning the pins on the board and on the plug and hopefully it will work. something tells me this is going to be a hard one to fix. the only thing i can think of that would make sense to me would be a bad connection on plug and socket. that or the motors in the gauges are completely out of wack...

ill check the resistance on the sensor tomorrow and give them a good cleaning and hopefully ill get it working again. thanks for the suggestion dan.

[mazdags94]

What exactly did you do with the clock? Did you move wires, did you do any soldering, etc.?

I ask because it sounds like your guages are grounding out, causing super low resistance, thus spiking the needle to the max.

The clock may be on a seperate circuit but it may be sharing a common ground with the other guages. Also, moving the harnesses around could have split open a couple of wires inside the loom causing them to short out, so you could check that out.

You could always try a new temp sensor as well. Theyre like 10 bucks. It doesn't sound like the issue to me, but it could just be EXTREMELY coincidental.

[mikeinaus]

all i did was take the gauges and clock from the new cluster and put them in the old cluster. when i put it together the first time i forgot to put in 1 or 2 of the screws for the temp needle. when i finally put them back in it was doing this.

i just played around with my voltmeter a bit and i think the motors are out of wack. if anyone is playing with there cluster and wouldnt mind taking a few readings to compare id really appreciate it.

1 wire temp sensor
car on/hot = 6.69V
car off/hot = 5.93V

screws for temp guage on back of cluster

car on/hot T-U to GND = 7.2V
car off/hot T-U to GND = 6.3V
TIG is the 12V power input.

gas gauge with low tank somewhere around 1/4 tank im guessing.
car on/hot F-U to GND = 1.86V
car off/hot F-U to GND = 1.64V
TIG is the 12V power imput.

i started playing around when the car was already warm so ill have to wait until tonight for it to cool down. but when i first started measuring the car sat for an hour before i fully warmed it up. temp gauge was around 12V and steadily voltage dropped as the car warmed up and the idle went to normal.

im going to fill up my tank after work and take readings again after my car has sat for a few hours and i can compare the readings. from what im seeing i think my sensors and harness is fine. i think the motors/gauges are just completely out of wack and need to be replaced. the temp gauge goes from cold to high in less then 1min of cold starting the car.

i also dont think i have a problem with the cluster housing itself as i have put the gauges back into the old one to see if it worked and im having the same problem. ive also disconnected the clock again to see if it was affecting the gauges and its not.

if this isnt bad enough the el light on the speedo gauge cover that caused all this mess just burnt out . so much work for nothing.

[mikeinaus]

i just took readings of the engine almost completely cold. its been sitting for 4 hours or so and is slightly warm to the touch but it gives enough info to tell the sensors are working fine i think. temp gauge was pointing near normal operating temp when i took these readings. start the car and the needle goes up almost instantly.

temp gauge cold / hot
car off T-U to GND 11.06V / 6.3V
car on T-U to GND 13V / 7.2V
temp sensor car off 11.07V / 5.93V

can someone please compare these readings, atleast the temp sensor V at cold and hot so i can confirm? that should be a large enough variance to give a different reading on the gauge wouldnt ya think?

on a side note my water pump is done. i just completely filled my rad and spent 10-15min trying to burp all the air out. i put the cap on and did maybe 20-30min of driving and when i checked with the engine cold the hose on the fill cap is pretty much empty... oddly enough my resevior is completely full with maybe 1cm from the very top. i dont get why it would be pushing water out of the system rather then pulling it in :S.

should i try that bars leak stuff or just spend all saturday replacing it? also herd a cap full of pepper or cracking an egg into the rad can help?

[Ryan]

I don't know WHY people think that the rad cap being empty means the rad itself is empty!

Coolant cools, and contracts, and the level goes down, if there is enough air in the system, it will cool and contract more than the fluid, and draw the stuff from the resevoir in...

Does your car leak? a lot of white smoke? Its probably fine.

If it leaks slow, it will draw in the from the reservoir.

If it leaks fast, you'll hear it.

[mikeinaus]

when i swapped the motor it leaked steam for a day or 2 then it went away. after i burped the system i was getting steam coming near the water pump. it may very well have been from the coolant that spilled during burping but the fact i dont have a working temp gauge scares me when i look in the fill hose and its completely empty. if this makes a difference my rad fan almost never comes on.

if the fill hose stays empty because of expansion/contraction wouldnt that just draw air into the system every time the car is run and require it to be burped again? should coolant spill out when i squeeze the fill hose with the cap off and the motor cold? squeezing it all the way i couldnt even see any water. however the return line under the rad fan was full of coolant and i could slosh it around from squeezing. is this normal?

[wytbishop]

The straight dope on the cooling system...

As the coolant heats up it expands. The rad cap is designed to open at a certain pressure..10.7-14.5psi on the K8. So when it opens it allows the expanding coolant to overflow into the overflow res. The tube in the res cap goes aaaaaaalllllll the way to the bottom so that as the coolant begins to cool, and contract in volume, it can suck up the coolant in the res. The res has a "full cold" and a "full hot" line. If you don't have enough coolant in the res when the engine cools all the way down it will start to suck air into the system.

Ideally there should not be any air in the system and when you remove the rad cap it should be full right to the top. What I have found is that the cap on my engine filler neck was leaking a bit. It took me a while to figure out why my coolant was always a bit low. When it's hot a bit of steam escapes from that cap and then as the system cools a little bit of air is allowed in thorugh it as well. So I would top my system up and a few days later I would notice that the res was down a bit again. What tipped me off...when I removed the rad cap the level would be down a bit but it would rise once I had the cap off. This told me that air was getting in somewhere above the rad cap. The only point of entry higher than the rad cap is the engine filler cap.

To properly fill your cooling system...

First fill the reservoir to the cold line. With the engine off and cold fill the rad right to the top and replace the rad cap. Then remove the engine filler cap and fill the engine. Leave the engine cap off and start the engine. This will circulate the air out through the open cap. Continue to fill the engine as it goes down until it stops going down. Replace the engien filler cap and go for a test drive to open the thermostat and circulate the coolant through the rad. Once up to temperature you should see that the reservoir is full to the hot line. I fit is not, it's just because some air was in the rad and got spit out intot he reservoir. Top it up to the hot line now and turn the engine off. After a couple of minutes you will hear the thermostat close as it cools. Then you will hear the coolant being sucked out of the reservoir as the coolant contracts. This takes several minutes. When it's done, the reservioir should be full to the cold line.

There is proobably noting wrong with your water pump, but I would look at replacing both caps. They're cheap and it will make your cooling system work better.

[mikeinaus]

ill give the caps a try and hopefully that will help with the low coolant. ive only ever tried to fill it from the engine fill cap. good to finally know the proper way of doing it. i must have a leak somewhere thow. doesnt make any sense to loose that much coolant and have the resevior completely full. seems like its pushing it out fine but its not sucking it back in. ill grab some new caps tomorrow and let you know how it goes.

[mazdags94]

Also, I had a water pump that when on me years back so they tend to leak under pressure (after you run the car for a while). It will start with a little bit and then eventually just start streaming coolant out from it.

TRUST me, you will know when your water pump goes! It's pretty obvious (coolant coming from water pump).

[SpatialTerror]

haha ok so hes got that figured out.
what bout the cluster?
s its still just ur temp needle?
could you post a few pics of what your looking at.
cuz if its happening on both clusters. its more than likely a sensor is freaking