Still Running Hot

[FDR Dippin]

'Sup guys,My '90Q absolutely hates the GA summer, when we start approaching 90F+, It's likely to start running hot (can get close to the 2:00 spot) according to temp gage on the cluster. This is isolated to idling.

What have i done recently?New Tstat, Water P, BG Flush (bottle), Prestone Coolant ~close to a 50/50 mix (tried the 70/30 mix but ran hot so i abandoned it), WaterWetter (even tho' i lost some when i abandoned 70/30 mix, CSF radiator, upper and lowerer hoses, Drive belts (1 mth old)...hmm what else, changed Rad cap (pepboys one, not Nissan). All of that above stuff was done about beginning 09/2005. I'm using 10/30 Mobil 5000.Fan shroud is on, belly pan is on!

What am i missing...?The only thing thats obvious to me is my fan blade, it has many cracks...and I've read of replacing foam surrounds by radiator but i don't know much about that.

Any advice, opinions is appreciated!

[Q45tech]

Condition of condenser and condenser fan, thermoswitch on radiator.

You need to give me a graph of temperature vs minutes in park and in drive to correlate with average.

Asssuming the idle rpm are correct the engine cannot throw off extra heat so something must not be as OEM BRAND NEW....................combination of non oem parts is usually the problem. an extra degree here an extra degree there and pretty soon over heat.

Condition of viscous fan control, the foam surrond at the radiator.

Not sure if you meant 70% distilled water and 30% AF as the optimum summer mix rather than 70% AF UGH.

Really you must provide exact temperatures measured at ecu sensor, and rad in, rad out.

Idling in gear at 650 rpm should be limited to 10 minutes if AC is on......what ever time it takes to not exceed 200F.

To make my 90 bullet proof I had a special custom rad manufactured 1999 by Griffin all aluminum and larger volume and changed the condenser and fan [multispeed set to medium] in 2002.

90Q only had a single speed aux electric condenser fan whereas later models had low and high and later 3 speed fan.

[FDR Dippin]

All parts replaced were NISSAN NEW with the exception of the rad cap and coolant. Idling rpm is OK.Ahhh a QTech post...it generates so many questions. Maybe i should just go to T3 heh...I'm seriously going to consider it once i return from my Honeymoon.

Is the thermoswitch the sensor that screws into i believe the left side of the radiator?

Isn't the condenser for the A/C, how would its condition affect engine temperature? Last I checked its fan was working <isn't that good enough?

**Also, I shouldn't say idling only** i should say little/no movement with little air flow, should i get stuck in heavy traffic or long drive thru line.

[Q45tech]

An old corroded dirty condenser can block quite a bit of air flow........A typical problem. Leaves, dead animals, hair between condenser and rad.

A aged distintegrated foam surround will alow hot after rad air to circulate back to the front of rad reducing efficiency.

For the system to behave as new it must be as new.

You said CSF rad vin first post now you are saying every part [but cap] is OEM NEW???

Is idle rpm at spec? 650-700 rpm in gear.

[FDR Dippin]

You miss nothing do you... But you're right, the Radiator is a CSF.There isn't any debris to talk about in front, however, i'll look into that foam surround...funny, i can't even picture it, even after replacing Radiator myself. It's attached to the radiator itself? What to replace it with? I saw another post that suggest even NISSAN's would be old and brittle now.

[maxnix]

Get the foam from Joe. Non OEM radiator caps usually are out of spec and fail early if they work at all. Good post by Jesda with pictures.

The good new is that you can take it to T-3 and get it and any other deferred maintainence problems diagnosed.

Oh, do you still have your under engine tray installed?

[elwesso]

Oh, do you still have your under engine tray installed?

'Fan shroud is on, belly pan is on!

I agree with tech, it could be that your car may not be running hot... We need to see what the ECU is seeing..

BTW JT, if you want your old account back email me, i sent you an email but you must not have gotten it.

[Q451990]

Oh, do you still have your under engine tray installed?

That was going to be my question... at idle the radiator fan throws the air pretty much straight down on the pavement if the road shield is missing... so then the fan sucks that hot air through the radiator again. Sort of a cascading effect...

When the shield is on the air is directed more to the back of the engine bay...

Heath

[Skibane]

What am i missing...?

Fan clutch. What you're describing are the classic symptoms of a fan clutch that is no longer providing an adequate mechanical connection between the drive belt pulley and the fan, no matter how hot the engine gets. Consequently, the fan never runs at full speed, and engine cooling suffers at idle and when driving slow.

Get an original factory replacement part - Most of the aftermarket clutches are crap.

[DrewQ45]

Fan clutch. What you're describing are the classic symptoms of a fan clutch that is no longer providing an adequate mechanical connection between the drive belt pulley and the fan, no matter how hot the engine gets. Consequently, the fan never runs at full speed, and engine cooling suffers at idle and when driving slow.

Get an original factory replacement part - Most of the aftermarket clutches are crap.

Skibane took the words right outa my mouth.... I think you should try changing the fan clutch. I have a used one in great condition and it would be cheaper to try it than buy a brand new one and still overheat if it's not the fix... I'm in ATL too.

[maxnix]

That was going to be my question... at idle the radiator fan throws the air pretty much straight down on the pavement if the road shield is missing... so then the fan sucks that hot air through the radiator again. Sort of a cascading effect...

When the shield is on the air is directed more to the back of the engine bay...

Heath

And wihtout the foam blocks, airflow can bypass the radiator/condenser entirely.
Modified by maxnix at 8:24 AM 7/20/2006

[Q45tech]

http://www.4s.com/fourseasons/...3.pdf

http://www.beta-cae.gr/05_chac...r.pdf

http://www.ricardo.com/downloa...w.pdf

http://www.aeromech.usyd.edu.a...6.pdf

http://www.me.up.ac.za/researc...r.pdf

http://www.me.iastate.edu/me43...r.pdf

http://www.delphi.com/pdf/tech...9.pdfOTHER:

Home computer rad but the test concept and results are the same:http://www.swiftnets.com/Techn...e.pdf

ATF Cooler info:http://www.daviescraig.com.au/...S.pdf

Hot air supercharger WARNING:http://www.kennebell.net/techi...G.pdf

Light reading that every radiator owner should understand before redesigning oem system by substituting non oem components.

Sure you are smarting than the team of 10 engineers that spent a year designing the cooling system?

[maxnix]

The second paper makes it pretty clear why the foam blocks and the under engine tray are useful, especially in a summer condition.

The last paper on hot under hood air should be qouted everytime a noob thinks he can design a better than stock CAI:

Quote »Finally, there's the removed headlight with the filter behind it (in the hot engine compartment, of course). This is just another "hot air" system. It remains underhood and blasted by hot fan air. At best, it's a hot air - cool air mixer at high vehicle speed as it does not - and cannot - pull in cool air.

Every engineer in the universe clearly understands the disadvantages of hot air and therefore designs their inlet systems to ingest cool dense air from the fenderwell, cowl or hood. This is not rocket science. JUST SUPPLY YOUR SUPERCHARGER WITH COOL AIR 100% OF THE TIME. All Kenne Bell supercharger kits connect to the stock cool air inlet system. [/quote]The article on water coolers for CPUs was most interesting. Flow rate of ambient air and heated fluid is everything!
Modified by maxnix at 9:11 AM 7/20/2006

[DrewQ45]

When it comes to cooling, I've spent many hours chasing down nuances on previous cars. There is usually one solid reason why the car overheats and it usually doesn't involve belly pans and the likes. Besides, I've seen a folks here run without them. Take the car to the dealer and have them diagnose the issue and state the cause. You can then fix it yourself...if possible.

[maxnix]

There is usually one solid reason why the car overheats and it usually doesn't involve belly pans and the likes.

Belly pans and foam blocks become critical when sytems are in marginal conditons, i.e. - highly stressed. Just because a car has no problems in 70° F air doesn't mean it's ready for 100+° F in the mountains or desert at high speeds or on steep grades.

AC failure in extreme conditions is known by everybody who has not maintained their unit. Cooling system failures are not far behind.

[goody90q45]

[QUOTE=maxnix]Belly pans and foam blocks become critical when sytems are in marginal conditons, i.e. - highly stressed. Just because a car has no problems in 70° F air doesn't mean it's ready for 100+° F in the mountains or desert at high speeds or on steep grades.[QUOTE]

Hadn't ever noticed the foam until you mentioned it. I took a look at my radiator and most of the foam padding is gone. Is it installed on all four sides and if so is it a continuous seal? Thanks

[Q45tech]

Unless you measure exactly you cannot judge improvements.

Unless you know what ecu is reading from its sensor you are clueless on the road [sure stationary you can open hood and use a IR gun to read coolant] but hard to get a tech to fit in engine comparment with hood closed..............midgets are expensive and they have a union......small children cannot be trusted and that's child abuse.

Engineers measure in 0.00F is it too much for owners to specify a single digit F number 200F vs 201F.

After all the human body 98.6F and 99.6F means something is a car any different whereas 1% would be 2F.

A 2 F deviation from norm in AC differential [amount input is cooled] is greater than a 5% error.........lots of difference between 47F and 52F center outlet temperature.

[1990Q45'r]

Sounds like viscous fan clutch. Spin fan blade hard by hand. It should stop quickiy.

[maxnix]

Belly pans and foam blocks become critical when sytems are in marginal conditons, i.e. - highly stressed. Just because a car has no problems in 70° F air doesn't mean it's ready for 100+° F in the mountains or desert at high speeds or on steep grades.

Hadn't ever noticed the foam until you mentioned it. I took a look at my radiator and most of the foam padding is gone. Is it installed on all four sides and if so is it a continuous seal? Thanks

Just the two ends to prevent cool air going around under way and hot under hood air recycling to the front when stopped.
Modified by maxnix at 7:25 AM 7/22/2006

[Skibane]

Sounds like viscous fan clutch. Spin fan blade hard by hand. It should stop quickiy.

...but only after the engine has been running for a while. On a cold engine, this test is inconclusive, since even a good clutch will allow the fan to be spun freely by hand. The difference between a good clutch and a bad one only becomes apparent when the engine is hot.

[sdkhalsa]

For most cars, the fan is not doing that much of the work at highway speeds. I would suspect that if a fan clutch has gone marginal then the cooling would settle down at highway speeds. How does this sound?

[maxnix]

Correct. At anything above 30mph not on an uphill grade, fan doesn't add much air flow.