Running Hot

[Jesda]

So today has been fairly humid, and we topped out at about 93 degrees. Stuck in traffic with the AC full blast, I noticed the needle was higher than usual -- 2/3rds of the way up, but it stays there until I start driving and it goes back to the center.

Should I have the coolant flushed and use 70% distilled water? Coolant flush is an easy DIY job that involves removing the drain plug, opening up the heater core, a going at it with a garden hose, right?

Off hand, does anyone know the coolant capacity in gallons?

Thanks!-Jesda

[elwesso]

Not exactly.....

I think you have other issues... I would guess a Tstat, which we can add to your list while your at my place...... Your radiator has been cored, and waterpump have been replaced... That leaves the Tstat...

[elwesso]

BTW, its 10.4 qts...

[Jesda]

[Q45tech]

Aluminum oxidizes inside and out. Rodding even chemical flushes does return it to 100% brand new.

In drive with AC [at 650 rpm] you will eventually reach the thermal capacity of system. The number of minutes tells you the time reserve above a stablized 180F..........some have zero minutes, some 5 minutes, and some have 20 minutes.............roughly an indication.

You can never trust the inside gauge as it is so damped and time delayed.

[Jesda]

Thanks for the info Dennis!

So, would you then agree, since my water pump was replaced, coolant was flushed, pulley was replaced, and radiator was cored, that the thermostat is the only factor left? I also replaced the radiator cap last year which helped quite a bit.

Right now Im running 50/50 water/antifreeze. I think I'll add a couple pints of water and change the other cap tonight.

Thanks again!

-Jesda

[Q45tech]

That amount [top horizontal mark is ok probably no more than 210F.......whereas normal is 178-180F.

Except that you have a 4 degree ignition retard from getting above 194.9F........makes for suggishness in acceleration.

Not the thermostat [90%] sure.......but you always change them every 4 years just to be sure.........unless you have a Consult then you can watch the temp change by single degrees and see the thermo go full open [by graphing coolant vs time] there will be a plateau in the graph of 1-2 minutes before the rise continues.

I must have spent 3 days last summmer just watching and graphing temp rises va ambient vs AC cooling vs time in drive with foot on brake.........poor mans temperature lab.

[elwesso]

Question for dennis:

On EF/EC 30, it says that if the vehicle speed is below 40 mph and the temp is 203-220 the fan operates at low speed.....

You indicate that this mark on the gauge is no more than 210... When my AC is on, I get the condensor fan coming on, and many times it is when the engine is COLD, so theres no way it can be up to 203*.......

How would you explain this.....?

[Q45tech]

The condenser fan also responds to errors in high side pressure and just AC ON in general.....the aux fan has 3 speed all under engine ecu control [in 94 and later].90 started out with single speed , 92 dual speeds relays driven directly from pressure and thermoswitches.

[HeavyDuty]

FWIW, Jesda, I'm now replacing my radiator, cap, t-stat, etc (because my radiator gave up the ghost a while back).

While investigating why it was running warmer than normal, I noticed that even though the car was up to temp (and slightly warm like your picture) that the fan clutch spun freely. If the car is up to temp or even warmer than normal, the fan clutch should not spin freely, but rather have a lot of reistance to you spinning it by hand.

I ordered a replacement clutch and the difference in resistance is night and day, even with the part new, cold, right out of the box.

I was going to mount an electric fan and dispose of the clutch fan, but sometimes they cause electrical anomalies in certain cars & I didn't want to aggravate the situation.

Spin your fan by hand hard (with the car off) & see how many blades pass the point where your hand lets go. If it's more than two, your clutch isn't working properly & the car might creep up temp at idle.

[Jeff Williams]

On a related issue, my clutch siezed yesterday, on the way to work.

I started hearing a louder engine sound, kinda buzzing. Then, when I got above 2200 RPM, the belt started to squeal.

I stopped, and checked the tension, but it was acceptable. It was not until last night, while removing the fan, to replace al lthe belts, that I realized the clutch was siezed.

I am getting a new clutch today, and possibly a new fan. It has a few small cracks in it, and I don't want it coming apart on me.

[pito11213]

So how do the Q gurus feel about going from clutch fan to an electric one. I have one on my t-bird and it keeps it pretty damn cool. You can have it on a thermostat system or a direct system with a switch in the car just with a relay. So what do you guys think about this?

[Q45tech]

The Q wasn't designed to supply enough electrical power to cool the engine without the mechanical fan..........you would be asking for real problems at idle with AC on high, headlights on as the aux condenser fan draws 15 amperes.

We all have enough battery and alternator problems, now.

You will need a 3000 CFM electric fan at the minimum that adds another 12-15 amperes:http://www.perma-cool.com/Catalog/Cat_page16.html

http://www.flex-a-lite.com/aut....html

16-28 amperes.

The Q alternator only puts out 34 amperes at fast idle [1300 alternator rpm --750 engine rpm]..........105 amperes at 5,000 rpm.....80 mph

[elwesso]

Jesda, if your fan/clutch is badd we can add that as well....

So Dennis, what your saying is, the condensor fan may come on regardless of temperature, but with the AC on, correct?? Meaning engine temp with the AC on is not the only factor in it coming on....

I would never replace the fan on the Q with an electric one, it pulls a TON of air!

[Jeff Williams]

Jesda, if your fan/clutch is badd we can add that as well....

So Dennis, what your saying is, the condensor fan may come on regardless of temperature, but with the AC on, correct?? Meaning engine temp with the AC on is not the only factor in it coming on....

I would never replace the fan on the Q with an electric one, it pulls a TON of air!

I just called the local dealership: $220 for a new fan clutch, and not in stock.

I checked, because I wanted to fix the car, tomorrow. Now I can get one from Joe.

The condenser fan operates, based on the A/C system requirements. It is there to reject the heat in the Condenser. I was not aware it is used for cooling the engine, as well.

One reason to swap the mechanical fan for an electric one, is to apply more HP to the wheels, rather than the fan, at WOT, off-the-line acceleration.

By the way, What gear do you have to be in, for the engine to be at 5,000 RPM, when going 80 MPH? Mine is usually running about 2,400 RPM at 80.

A good argument for not worrying about the amp draw, is that the battery can supplement the alternator, when the car is at idle. Then the alternator can replenish the battery energy, when on the road. The problem comes in, when the car is in heavy traffic, with little or no chance of high RPM's.

There are a few new fan designs that give the proper cooling for a 400+ HP engine, that draw less amperage. There is an add in the "Classic Trucks" magazine this month, even.

I just wish I didn't HAVE to replace the fan clutch now. I might try an electric fan.

[Jesda]

I tried HeavyDuty's spin test. It went about 2 and a half blades past where I released my hand. But I didnt feel a whole lot of resistance. Looks like I'll do that and that T-stat this summer.

-Jesda

[Jesda]

Yesterday I had the coolant flushed at a gas station. They run just water, no chemicals, and refilled with a 50/50 mix.

Its perfect now! I can idle in traffic on a hot day without having to turn on the heat.

-Jesda

[Q45tech]

Seems strange didn't you have the rad pulled when the guides were done last month? Mini drain/flush.

When rad is out use shop air to blow thru condenser to clean it out.

[Jesda]

Just for reference... in case anyone searches this thread later.

The problem came back, so I drained the radiator, added all distilled water. Improved slightly. Changed both radiator caps from Stant to CST. Both had the locking lever but the CST was the only one that stayed on securely under pressure -- so avoid Stant for rad caps.

Then the upper radiator hose sprung a leak, squirting coolant all over the place, so I replaced that yesterday.

Finally today I changed the t-stat (new one is a Stant) and the problem is officially solved, all for 9 bucks and a little patience.

-Jesda

[Jesda]

I also dropped the old thermostat into a pot of boiling water and left it there. It didnt budge. I have no records of it ever being changed since 1992.

[redmanfx]

I just changed my cooling fan, upper and lower hoses, added Niassan green and Water Wetter - Wetter Water or whatever you call it. Since then all seems great, but I did not change the t-stat.

Mine's a 92 and it seems to be breaking all the rules by original parts lasting so long. Should I just change the t-stat because it's so old?

red

[DAEDALUS]

Closed failure! So it does happen. Red if you'll be replacing the rad hoses it isn't too much additional work to do the t-stat. Luck isn't associative, just random.

[Q451990]

Closed failure! So it does happen.

First I've heard of it on a Q too! My mom killed an '82 Mazda 626 with a closed t-stat though.

Heath

[Q45tech]

I change my thermostat and 3 rad hoses, belts every 2-3 years [~~30-45,000 miles] with genuine Nissan parts which I pay for ............no junky parts allowed no CST, stant. Napa, Advance, AZ, etc.

Just like clock work, the minute I added 67,000 miles [4 years] my valve covers started leaking a tiny bit AGAIN after the 200k reseal. Counting down to the 3rd plenum hose replacement prior to 300k..............will they start leaking before the next 33,000 miles [2 years at present driving rate].

[hh11011]

Make sure to use an OEM thermostat. It has incorporated a jiggle pin necessary to bleed air from the engine! Stant and others don't have this feature.When installing a new thermostat the jiggle pin facing must be straight up for it to work properly.

hh11011

[natsoundup]

On safety, PIA projects, and overheating issues...I would always use OEM.

Brakes, Alternator, and Thermostat would fall under those guidelines for me.

I changed a thermostat out after 11 years on the 90 and was amazed at the pristine condition it was in...and how heavy a gauge metal that was used. Changed it out just because I decided to do the hoses after 11 years, too...

[elwesso]

I agree with nat.....

When I replaced my Tstat it looked FLAWLESS, and I dont think it really did anything when I replaced it except for piece of mind...

[Jesda]

The Stant 170F thermostat does have the jiggle pin, and I rang Wes before installing it, so the pin is at the top. My next move is to replace the hose and pipe that goes from the radiator into the thermostat housing.

Normally I prefer OEM, but the cost of next-day shipping from Joe for a $7 part didn't seem like a reasonable move. Plus, the local parts guys were on strike. I headed to Advance and spent that shipping fee on some RTV instead.

If it lasts 3 years, I'll be pleased. With a fan blowing on me, some country music, and a cool beverage, these DIY jobs are relaxing -- like productive meditation -- and I don't have to wait a week for the dealer to fit me in their schedule so they can rape me for $90/hr (they [Bommarito Infiniti] do excellent honest work, however).

-Jesda

[elwesso]

Im pretty convinced that aftermarket thermostats are pretty close to OEM..... I would personally go ahead and replace it with OEM in a year or 2 anyway... You dont want a simple part like that failing.....

[Q45tech]

Dream on, we change lots of thermostats and crappy filler caps and thermo caps..............the rubber seal and jiggle vavles are different on oem/Nissan.

Old used = Look good but do you do the exacting temperature vs % opening test......3-4 degrees is significant in summer performance.Whether the heater varies 3-4F in winter wouldn't be noticeable.