I decided to hook up my laptop to my car since it was in there and while the engine was running, I noticed that the dash temp gauge was reading just under the half mark but on the computer, it shows that the engine was running at 217 degrees with an outside temp of 84 degrees.
Modified by mattd1979 at 12:54 AM 9/12/2009

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... Q45Tech said something to that excent at some point...

How long were you idling? I would be concerned if it wasn't long, especially at that low of an ambient temperature. Having the laptop plugged in sitting in a long line at a drive-thru can make an otherwise boring wait very interesting - watching the temperature climb and climb.

Heath

I had been there about 10 minutes in the driveway. It was starting to get dark out. I hooked up the laptop to see what my o2 sensors were doing and I noticed the temp reading and I remembered what Q45tech said about how the engine starts doing funny things after around 197 degrees. Earlier when I was driving, I noticed a lot of spark knock when I was getting on the interstate. I couldn't go more then half way with the throttle without getting heavy pinging. All I run is 93 octane from BP with ISO-HEET and I never noticed it doing it that bad, so when I got home and hooked up the computer, that is when I noticed the engine temp. I know that as the temp rises, you have a higher chance of spark knock. I guess I'll be looking at swapping in another thermostat I suppose.

The purpose of thermostat is to warm car up fast not to keep coolant cool.The point is above 194F the thermostat is wide open and any rise above that comes from a not up to spec radiator [air blocks, condensor blocks, air leakages around not thru] and or water pump fin wear.

Gasoline has a ambient temp vs knock sensitivity graph known only to refiner per hourly batch.............after dozens hundreds of batches are blended in pipeline and local storage tanks who knows.

217F is beyond the feedback control point of 215F so 5 degrees of static advance has already been removed by ecu and you are near the point of thermal runaway.

Years ago I attempted to derive a wear rate for radiators. How much less efficient they become with age as fins bend and oxidize inside and out. It was a loosing battle to analyse things without destructive testing.

It appears that oem radiators need to be replaced about 7 years or 100k if 85-90% of brand new efficiency is expected.

In summer a fresh 30% AF/ 70% distilled water can improve thermal transfer efficiency by 3-4% and drop coolant temperature by the same 3-4F.

Ideally the radiator should provide enough cooling so that the thermostat can cycle the system to midpoint or closed 174> 184F> 194F fully open.

Measuring the temperature rise per minute in drive after stopping with ac on is critical since a 3 minute light traffic may leaving you without emergency acceleration in a marginal worn system.

On a 100F day [110F road air temperature] how many minutes can I stop and idle in drive then what is my acceleration potential without jnock or reduced ignition advance?

I get 3 minutes +- 10 seconds before I exceed 195F with a massive custom radiator installed in 1998.........even the Griffin is starting to show age after 11 years and 160,000 miles. But less than half the rate of oem at same mileage and age [8.5 years].

Idle speed in drive ac on is critical to heat generation [fuel burned].

Many do not realize that E10 is significantly lower in BTU than the fuels we could purchase in the 90"s............it takes almost 10% more fuel to generate the same heat.

This was done to increase domestic gasoline supplies [more gallons from fewer barrels of oil] not all at once but in a steady progression.

This can be seen in the steady cruise MPG and the ecu ignition advance at 60 mph [up to 43 degrees now vs 41degrees on real gasoline years ago.

Ecu advances until knock then backs off [cycles every 200 msecs] . Less heat needs more advace to compensate for slower flame speed.

mattd1979 wrote:I had been there about 10 minutes in the driveway..... I guess I'll be looking at swapping in another thermostat.......

The thermostat fails open so it's not the cause of your high temp. How's your fans working? Are you hearing the electric fan switch on/off? Is the fan clutch operative and spinning at full speed at idle?

I've watched the engine temp rise and followed it on my laptop. The needle hits 3 o'clock at about 160* and doesn't move all the way up to 200*. It must start rising again above 212* but I've never had any of my Q's overheat or had the temp needle rise above 3 o'clock.

As I was reading Q45tech's post, I thought about the clutch fan. I did hear the electric fan cut in and out and I had replaced my water pump back in february due to bearing failure. I filled the system with 50/50 premixed coolant. I am going to hookup my laptop to the car and drive to see how it does on the interstate. A few weeks back one day I left the car idling in the driveway for about 10 minutes and the temp outside was somewhere around the upper 90's. When I got back to the car to leave, I noticed the temp gauge was reading 3/4 of the way up. I eased on the gas and got up on the interstate easing the speed up to around 90 and put it in neutral and coasted down the bridge to my exit to help cool it down. the gauge dropped below the half way point when I got off of my exit.

3/4 of the way up is a big problem. Is your road shield installed?

Heath

mattd1979 wrote:...... I am going to hookup my laptop to the car and drive to see how it does on the interstate.

......A few weeks back one day I left the car idling in the driveway for about 10 minutes and the temp outside was somewhere around the upper 90's. When I got back to the car to leave, I noticed the temp gauge was reading 3/4 of the way up......

I'm going to guess that she'll run nice and cool on the highway but as soon as you exit and get in stop and go traffic or sit in the driveway it's going to heat up. Fan clutch- Is the fan spinning at idle or barely moving? You can check it by loosening the belt and rotating the fan manually. There should be a lot of resistance and it should definately not spin freely.

Here is my findings after idling the car for 53 minutes.

With A/C on and an outside AMB of 78 degrees F and a cold engine idling.

Needle doesn't start rising until 125 degrees. When the needle points at the beginning of the scale (base line) on the dash, the temp is at 130 degrees.

145 degrees after 6 minutes.Temp gauge stops climbing at around 160 degrees.167 degrees at 10 minutes.185 degrees at 15 minutes.condenser fan engaged.Engine RPM picked up from 700 to 800.200 degrees at 20 minutes.208 degrees at 25 minutes.212 degrees at 30 minutes.218 degrees at 35 minutes.Temperature begins dropping when RPM is raised to 2,000.Temperature drops to 208 degrees at 40 minutes.Temperature climbs back to 212 degrees in 3 minutes at 43 minutes run time.214 degrees at 45 minutes.Oil pressure at 52 psi with engine rpm at 2,000.219 degrees at 50 minutes.Opened hood and with engine still at 2,000 rpm, temperature dropped from 221 degrees down to 208 degrees in 3 minutes. During all of this, the gauge never climbed any further since the time that I reported that it stopped after reaching around 160 degrees.This is a bit scary as my temp has been up a little above 3/4 of the way a couple of times as I mentioned in a previous post. The engine hasn't given me any trouble so far fortunately.

My battery in my laptop went dead so, I couldn't get any more readings to see how much more the temperature would drop with the hood open at 2,000 rpm.

Matt

Pretty common numbers on old Q where component replacement has not occurred at 10 year intervals.

New oem radiatorNew oem condenserNew rubber and foam surrounds to seal core air from escaping around rad.New plastic fan blades

You have seen the PROBLEM that the inside temp gauge doesn't tell you anything except the engine has warmed up. AFTERALL with every 90 day trips to dealership and unlimited funds every marginal thing would be constantly replaced so there would be no way for an overheat.

I always recommed that owners install a contact cylinder head temperature sensor to watch what is really happening

mattd1979 wrote:.......I thought about the clutch fan. I did hear the electric fan cut in and out and I had replaced my water pump back in february due to bearing failure.

Interesting numbers you posted and it looks like you're running 10*-15* warmer than you should be at idle. Did the electric fan go on/off at any time during the idle test?

Seeing that you've replaced the water pump already have you checked the fan clutch operation with the belt off. With the belt removed there should be some resistance when rotating the fan blades by hand. If the blades are close to free-wheeling then they're not running the full rpm's at idle (with the belt on) and not pushing enough air through the radiator.

Which consult program are you using that gives a readout for oil pressure, or do you have a gauge installed? It would come in handy for me right now.

215 F is the maximium Nissan ever expected out of an INSPEC Q45 while the normal operating temperature is the midpoint of thermostat range.

174> 194F = 184F.....................that's 30F ABOVE NORMAL.

Obviously the rad caps 13 psi limit was the final safety

I have a mechanical gauge installed. Down the road I'm going to install an electric gauge that uses a mechanical sending unit so that I can do away with the copper oil pressure line. I'm going to collect temp readings while I am driving to the beach which is about 25 minutes at an average of 60 MPH to get a comparison. My next step will be to invest in another fan clutch. As for the electric fan cycling, it actually cycled on and stayed engaged until I shut the car off. I mentioned in my previous post that the temps instantly began dropping as soon as I opened the hood. That would explain why some of the police cars that you see parked while running have their hood popped.

In my previous post I mentioned that the temp gauge has risen up over the halfway point to 3/4 of the way in the past but I didn't have a laptop then to connect and see what the ECU was seeing. Being that the temp climbed to over 221 degrees yet the gauge was still under the half-way point makes me wonder how hot it actually had to get in order for the gauge to read up to 3/4.

Alright, On the way to my sister's house at the beach, I had my laptop hooked up and was monitoring the temp on the way there. The outside AMB was 85 degrees and I was driving at 70 MPH steady for about 10 minutes and the temp would go up to 196 and then go down to 192 degrees in that range. At 50 MPH for another 10 minutes, the temp would climb and then drop from 192 to 187 degrees.

Have you replaced the fan the viscous clutch?

How clean is the radiator?

I haven't replaced the fan clutch yet. I wanted to wait until I compared the readings of the temperature while driving (which I posted yesterday) to the readings I got from it idling in the driveway. From what I can see without removing the radiator, it looks pretty clean to me. I didn't notice any dirt or any bugs caked up on the front. I know... that is not the only determining factor when checking on the cooling efficiency of the radiator.

I used a baking thermometer probe that I slipped in between the fins of the radiator to get a comparison of the surface temp to the fluid temp of the radiator temp sensor. The highest it read was 147 degrees. My brother is coming into town and has a infrared thermometer that I am going to have him bring with him.

I've driven around in all 3 Q's I've owned with the consult plugged in and never had a reading anywhere close to 200+ degrees. I might have seen 190* once on the warmest of Sacramento days. Something is not quite right with your cooling system (but you already knew that).

Comparing your driveway #'s to the highway #'s it looks like you're borderline on the highway (radiator efficiency) and have a problem sitting in the driveway (fan clutch/radiator efficiency). Makes me think that the 15-20 year old radiator is not too efficient and could use a DIY cleanout (chemical flush) or maybe replacement. Did the thermostat get changed? How does the fan clutch feel?

I hate to admit it but I think I'm repeating Q45T*ch's advice.

Do you still have the road shield still installed on each of your 3 cars? I wonder how many out there on this site has their's installed. I still have mine but I've kept it off.

On the 3 that I've owned and the 3 that I've parted out I've only seen 1 road shield and it was dragging on the ground and removed. I've never had any overheating problems.

Up until now I hadn't either, of course I didn't have what I have now, a laptop and the consult cable so that I can monitor my engine temps. Have you had to replace any of your radiators or fan clutches? If so, how many miles did you put on them before replacing?

Matt

Two of the 3 fan clutches from my part out cars were bad. Both had about 150k miles.

Fan clutch and radiator are both easy to change. First ting to do for both is to remove the curved fan shroud.

You don't need to do anything to check the fan clutch except loosen one idler pulley. Next you'd want to move on to a radiator flush and you'll only have to get to the spigot at the bottom of the radiator for this.

Check your fan clutch first. I think it's lost its grip.

I was just wondering how many miles you had put on your radiators and fan clutches before having them replaced. Q45tech says that it is best to replace the radiator every 100K.

goody94q45 wrote:.....You don't need to do anything to check the fan clutch except loosen one idler pulley......

I was mistaken in telling you to loosen the fan belt to check the fan clutch. No wrenching is involved. Just turn the fan blade by hand. If there's no resistance the fan clutch needs replacing. If you can feel it pulling back it's probably OK. I'm sure there's a more scientific way to diagnose it in the FSM but this "quick check" will get you started.

Actually, your version is more scientific. The FSM only states to look for leakage around the shaft and for play. I spun the fan when the engine was cold and it spun 180 degrees. I did this again after the engine was hot and it spun 90 degrees.

Matt