I30 Overheats

[bvehorn]

I want to thank all the resident experts who take the time to help the rest of is out. I've learned a lot about my J30 and I30 from reading these forums.

I wanted to ask about the possibility of a water pump going bad. My 1999 I30 started overheating on the way home yesterday (the indicator was pegged before I even noticed it). I parked immediately and had it towed home. Today I replaced the thermostat, which has always been the culprit when I've had this happen on other cars. My experience has been that the water pump will start to leak before it actually fails. But the temp gauge still heads straight for the top as soon as the car warms up. The radiator is full, but I don't see any water movement in there, nor is the water hot.

Do I need to replace the water pump, or is there something else I should check first?

Thanks in advance!

Bob

[loystock]

Welcome to NICO.

Based on symptoms provided and the fact that you just replaced the thermostat, your water pump most likely has failed. Please refer to the attached link for coooling system info and how to replace the water pump.

http://www.nicoclub.com/FSM/i30/1999/lc.pdf

[bvehorn]

OK, thanks for the info. Having the FSM available makes all the difference. I also found this YouTube video, in case anyone else is looking at doing this:

[youtube]http://www.youtube.com/watch?v=ibfs1Zu9 ... creen&NR=1[/youtube]

[NutriaforBreakfast]

Pull radiator and see if its stopped up with gunk

[bvehorn]

Interesting that you should mention the radiator. I replaced the radiator cap when I did the thermostat. So before replacing the water pump I ran the engine and it did not overheat. I topped off the coolant and drove it around the neighborhood, and the Temp gauge started alternating between half scale (normal) and full scale. As if a wire was loose, or shorting out (according to the FSM, higher temps result in lower resistance). So I took off air intake and started checking resistance of the Thermal Transmitter, when a stream of water started shooting out of the top of my radiator. So I've got a radiator on order and I'm still trying to work out what's wrong with my cooling system and/or Temp gauge.

[bvehorn]

OK, I've got a completely new cooling system... radiator, hoses, thermostat, water pump, and thermal transmitter. The fans come on when they should, the system holds pressure, and I'm not losing any coolant. BUT, my temp gauge still reads from half scale when cold to full deflection when it warms up. Except when it doesn't. What I mean by that is that occasionally it will indicate normal temperature, like it did before the engine overheated from the cracked radiator.

Today I pulled the instrument cluster and checked the resistance of the gauge. It read good according to the FSM (103 ohms A-C, 134 ohms B-C), and it reads good in diagnostic mode. The connector on the thermal transmitter (F25) looks like crap. I couldn't get to the continuity checks before it got dark, so that will happen tomorrow. But it seems like there's an intermittent short somewhere. Has anyone experienced this before? I just can't see where the problem could be, since the sensor wire goes straight into the main wiring harness. Hopefully I'll know more after the wiring checks. If anyone has any tips or suggestions, I'm all ears.

Cheers!

[bvehorn]

Wiring checks this morning confirm a short in the wiring somewhere. I have good end-to-end continuity, but when I check from the open wire to ground I get a reading of 65K ohms. That would explain the erratic behavior of the gauge. Anyone have any ideas where to look for the problem?

Thanks!

[bvehorn]

Wiring checks this morning confirm a short in the wiring somewhere. I have good end-to-end continuity, but when I check from the open wire to ground I get a reading of 65K ohms. That would explain the erratic behavior of the gauge. Anyone have any ideas where to look for the problem?

Thanks!

[bvehorn]

Well, I've isolated the problem to the "M" harness, between M50 and M29. Going to run a separate wire and see if that fixes it.

[bvehorn]

OK friends, time for some analysis. I'm hoping to hear from some of you experienced Max/I30 folks...

I ran a direct wire from M50 to M29 (at the back of the instrument cluster). Got good continuity from M29 to F25 with no continuity from either connector to ground. And I installed the new gauge that I got from infinitipartsusa.com. The gauge is still intermittently jumping up to max deflection. The voltage at pin 14 on M29 stays within about 2.5 to 3.0 vdc, whether the gauge is reading correctly or not. I also monitored the resistance of the thermal transmitter over a 10 mile test drive and it was consistent with the values in the FSM. My fans are operating normally, and I can see the voltage/resistance change when they come on.

It's very disturbing to be driving down the highway and glance down to see the temp gauge pegged at HOT. I've tried everything I can think of, but am still having this problem. I could use some ideas...

[Gertrude73]

Having the FSM available makes all the difference.

[bvehorn]

Having access to NICO makes all the difference, too. I found the following quote on the Infiniti Technical forum:

"The dash gauge is notoriously inaccurate. If you see it above the halfway point you're in real trouble. I think it's designed to be non-linear (lingering around the halfway point) to keep from alarming the driver..."

It's attributed to Q45Tech, though the post was from someone else. So it's possible that I am running hot. Closer inspection and a little testing showed that the gauge is not actually maxed out, but just below full deflection. It's never done this before it overheated a couple months ago. Anyway, I've got a scan tool on order and will know more by the end of the week.

[bvehorn]

Well, the good news is that my I30 is not running hot. The ScanTool software reads 185 to 190 degrees while driving in all conditions. It did reach 205 while sitting at idle without the A/C on, but at that point the fans came on and brought it down 10 degrees. I purchased the OBDLink SX 2.0 from ScanTool and recommend it as a great tool to have in the toolbox.

Happy Trails!