Temp Gauge Rpm and Mpg gauge

[Since88]

So here's my story...

Just acquire my first bmw (newbie) about 2 months ago 88 325ic..165k bone stock.. Recently just did the timing belt and water pump..my question is the mpg gauge and rpm plus the temp gauge sometimes doesn't work. The funny thing is that it work for the rpm and temp when I do the "tapping" trick and it will bounce back to working condition. With the temp gauge I noticed it creeps much closer now to the 3/4 line which got me a little concerned because b4 the water pump was change, the temp need would sit just a hair left of mid point and just a hair on right of center when sitting or idling. After the repairs it creeps closer to the 3/4 line.

Read on forums it could be air in the coolant system, temp sensor, gauge faulty, bad so batteries?

[jlevie]

Having to tap on the gauges to get them to work could be dirty gauge needles that are sticking to their stops or cracked solder joints in the cluster's PCB. If it was just the temp gauge I'd suspect the nuts where the gauge mounts to the PCB.

It could be that you haven't properly bled the cooling system, procedure below. Or the thermostat could be bad.

1) Using ramps or a jack get the front of the car 1' or more higher than the rear. That will make the radiator and bleed screw the highest point on the engine and facilitate removal of air.

2) With the bleed screw open, add coolant until no more air comes out of the bleed.

3) Leave the filler cap off, or at least loose, and set the heat for max temp and fan speed. Leaving the cap loose will prevent air that's still in the system from causing a "coolant fountain" once the engine heats up. Start the engine and allow it to warm up to operating temp. As it warms up occasionally crack the bleed screw to release any air and top up the coolant as necessary.

4) Once the engine is at temp bring it up to 2000-2500rpm for a few seconds several times. Then crack the bleed until no more air is released. At this point the heater should be throwing lots of hot air, which indicates that the heater core is filled with coolant. You may have to repeat this a few times to get all the air out.

5) Drive the car a bit, allow it to cool back down, and recheck the bleed for air. Over the next few days you may get very small amounts (a few bubbles) of air out of the bleed screw.

A vacuum fill bleed system makes filling and bleeding the cooling system a trivial task. But the procedure above will work if you don’t have access to a vacuum fill system. On an E30 and some other BMW’s you can speed up the fill process by removing the small hose that runs from the coolant reservoir to the top of the radiator at the radiator end. Then fill the reservoir to the mark, screw on the cap and blow into the hose until coolant comes out of the radiator nipple. That will fill the engine and radiator with coolant pretty quickly. It may take more than one fill/blow cycle to fill the radiator. Then bleed as per above to get any remaining air out.

[Since88]

Thanks for the advice..I know now where to start.

[ak-]

Happened to my friend.

Re-soldered the contact point behind the gauge and now it sits a hair below half at idle like it's suppose to. Need to do this to mine considering my needle waves at me sometimes.

[Since88]

I wish I had a soldering iron around and soldering skills.

[ak-]

I wish I had a soldering iron around and soldering skills.

You can buy one at the .99c store/mart, or any harbor freight for like a few bucks.
The area you have to solder is C-shaped and indented so all you have to do it touch it with some soldering wire and it sets itself in.

Don't be a weenie and just do it. How else will you learn!