NanaimoRx-7

This one is baffling me. I just replaced the radiator last week as it sprung a leak, got it recored, put it back in and everything was great for a few days. While the car was down I also bought some Bosch H4's lights to replace the crappy sealed beam lights.

The first night I had my rad back in I took it out to test the lights and generally give it a good flogging. The temps were rock solid all night in that usual place between and 1/8 and 1/4 on the temp gauge. Couple days later on the way back from a drive it started getting dark so I flipped on the new lights, man they look great, couple turns later I glance at the gauge and it's 3/4 of the way up!!!!! I got off the gas right away and quickly realised the only thing I had changed in the last few minutes was the lights, so off they go. Temps start falling.

I really don't understand this at all, I can drive along with normal temps, hit the lights and within 60 seconds be to the halfway mark on the gauge. If I turn them off it'll slowly fall back down to it's normal spot. The same effect came the other night from turning the heater ON. I was guessing glazed belts slipping with load applied to the altenator and not spinning the water pump, but I just replaced those today and it's still pulling the same trick. Now I also have a leaky oil cooler, but I'm having a replacement one shipped in the next few days, but I can't see that being the direct cause of the problem. I'm kinda lost on what to do here. I think I'll take a peek at the thermostat tommorow, but I just replaced it recently (within the last 6 months). Any ideas? Thanks in advance, George.

AdrenalifeRX7

Do you have an electric cooling fan?

KYPREO

The water temperature gauge is electrical - it needs power to function accurately. If the alternator is loading up (from heater on, spotlights etc) and there is little system voltage, plus the gauge itself is rooted, it will give a different reading. Perhaps the temperature is the same, just the reading is different?

This is one of the reasons mechanical temperature gauges rock.

Electricity is setting off the overheating, electricals are the problem - either the gauge or an electric fan fault like adrenalife said.

onepointone

your low on headlight fluid man... what are you thinking???


seriously though, i agree with KYPREO, its probably staying the same, just the gauge is reading wrong.

zaridar

iTrader: (3)

Could be that the new loghts are taking a ton of juice so the alternator kicks in all the time and the engine it working harder

zaridar

iTrader: (3)

that sounds kinda dumb but it is the same with high power stereos. They kick in the alternator. Howver i dont know if this actually would make the engine work that much harder. It does have to hord harder though.

Cody

Yeah, its just the gauge.

The other day, I took off the belts for the A/C and the airpump, and just had a single belt running the fan and alternator.

For the first time ever in the car, the temp guage read about half, maybe a little more. It's usually like you said, at the 1/8-1/4 mark.

I wondered why it would have changed.....but, to be sure, I pulled over, turned it off, and looked around. The belt was new, and not squealing or slipping, so, I figured there must not have been a problem.

Got back in, started her up, and the guage read back to the normal 1/8-1/4 spot for temp.

I think, being electrical, the guage just acts up with a different load, like the other guys are saying.

NanaimoRx-7

Hmm interesting I thought about that too, but I wonder why it didn't do it the first night I had the lights...

I was thinking about getting an Autometer Sport Comp 2 5/16 mech water temp gauge and putting it in the air vent left of the steering wheel. I remember measuring a long time ago and thinking it would fit. It does seem to come up too fast to be real, but it still scares me enough not to drive it at night like this.

Ultralights

I have had the same problem, the more electrical load on the system, the hotter the guage reads, when it raining, with lights, wipers and air conditioning on, the guage is way into the red, yet stop at lights, turn everything off, and the temp comes down real quick. it only started happening when i changed the rating on the headlight bulbs from 55/60 to 60/100.

i installed another temp guage and it never moves.

anthrax

I just installed the H4 Conversion, and have a High power sterio, I am not having any problems. But man this is all stuff to concider. I want to put in and elctric fan. Eh maybe just put in a bigger alt. Who knows

NanaimoRx-7

So say I pick up the autometer mechanical water temp gauge, is it okay to use the lower drain plug on the engine to get my readings? Will they be accurate enough? And what thread is that bolt 1/2 NPT? Thanks.

NanaimoRx-7

Any more thoughts?

/waits for Rx24/7Carl to show him the light

Suparslinc

Okay, we are getting some conflicting reports. Some people say with more electrical load the temp gauge reads higher, some are saying lower. I don't know what to tell you.

I've had my car for 8 years, 3 engines, and the temp has always read just below the thermostat mark. Until I removed the A/C, PS, and some other. Now the temp creeps a bit on the hiway or under hard runs.

So what I'm guessing is

less load = higher temps

But this is exactly the opposite of what you are describing (and it makes no sense, right?).

You have to realize that the wiring on these cars is 20+ years old, I know very little about electrical stuff but you are probably putting a tremendous load on the system with your new lights. This could affect the readings; it's all integrated.

My first suggestion is to rewire the headlights.

Ultralights

i had the same probelm with my Series 2, i just replaced all the wiring between the battery and starter motor, and while doing this i tightened every earth lead i could find, i also cleaned every electrical terminal i could find as well, and Guess What! Temp reading problem solved.

Most problems like this are usually bad earths.

82transam

iTrader: (18)

yea, bad grouds **** **** up big time. like ultralights said, replacing the battery cables might not be a bad idea.

KYPREO

guys, its a factory electrical gauge thats 18-25 years old - it never was and never will be very accurate.

Also keep in mind it is on the "cold" side of the engine, so it may register temperature changes that may not have the effect you expect.

I recently installed a 2 5/8" mechanical water temp gauge and when you see the temperature on the "hot" side of the engine (ie thermostat housing) you find the temperature is actually very consistent. Meanwhile, the factory gauge is all over the place. 85 degrees C (185F) on the mech gauge corresponds to anything from 1/8-1/3 on the factory gauge. Having both is still nice however.

As for the load an alternator places on the engine, well its not enough to cause it to overheat. At max load the alternator will sap around 5-7hp at mid-high rpm. In lower rpm, the power loss is a lot less. Keep in mind that there is "floor" level of load that is required to keep up the current requirements of the ignition and fuel system - the load in other words is negligable, and would NOT cause any overheating from engine working harder. You can add 200% extra engine output without even taxing a well maintained RX7 cooling system with a factory clutch fan.

You can install an autometer gauge in the temp switch hole in the thermostat housing, however, you will need a metric adaptor screw, as the 3/8" NPT adaptor is slightly too big. Find a pic of my sendor install attached.