I have a 90 Q45, 106k, I have had everything gone over by Jerry Tucker and have replaced most major systems. My problem is the cars temp gauge seems to creeps up a few degrees in the heat zone when the engine is fully warmed up and at high speed (85+)on slopes (freeway), or when fully warmed up at a short 1\2 block but quite steep uphill in hilly neighborhood. The temp gauge spikes up from the just-below-3:00 position to the nearly 2:00 position, when I back off and slow to under 70 or level out the temp returns to normal quite quickly. This car runs great otherwise. What might cause this spike in temp at max load?
Thanks in advance (This is a great resource)
crubio
overheating at heavy load.
I would get to the bottom of this! Jerry Tucker has a great reputation, and maybe it's time to pay him another visit, because this doesn't sound like normal behavior. Overheats are deadly to the aluminum motor and many of its important parts, like the horribly expensive and expensive-to-get-to knock sensors!
The car Is at Jerrys shop right now. I'm just doin a little research as I have this great resource and you guys offer great imput. Thermostat has been replaced as well as all coolant hoses and new fan clutch. Jerry thinks it could be the radiator also. The radiator is fairly new with about 20 k on it. Overheating is my biggest fear. I'll keep you guys posted.
Thanks
crubio
Thanks
crubio
My recommended coolant fill for anything but a northern winter:
70% distilled water1 bottle redline wetter water (=3.5%)rest antifreeze.(=26.5%)
Too many PPL run their mix too thick.
I once had similar behavior in a 92 a few years back only to find out that the it was filled with 80%AF and 20 water
Assuming no other issues are found:
Do a couple of radiator flushes before u refill it and <be sure> to use only distilled or deionized water to refill.
If the radiator is that new and it tunrs out it is inded a rad problem even a non OEM should still be ok (even tho they are not as good as OEM)
In the absence of other indicators, I suspect some very hard tap water may have been used in its original fill
Fred...
70% distilled water1 bottle redline wetter water (=3.5%)rest antifreeze.(=26.5%)
Too many PPL run their mix too thick.
I once had similar behavior in a 92 a few years back only to find out that the it was filled with 80%AF and 20 water
Assuming no other issues are found:
Do a couple of radiator flushes before u refill it and <be sure> to use only distilled or deionized water to refill.
If the radiator is that new and it tunrs out it is inded a rad problem even a non OEM should still be ok (even tho they are not as good as OEM)
In the absence of other indicators, I suspect some very hard tap water may have been used in its original fill
Fred...
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Q45tech
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Wetter water doesn't lower the coolant temperature on a Q, it raises the heat tranfer from the heads to the coolant. Thus the coolant temp sensor will show a 2-5F increase under load now the radiator may be more efficient due to the incoming air vs higher input coolant temp but this usually washes with the coolant temp going into the engine being 1-3F colder.
What you want is colder heads not necessarily colder sensor reading!
What you want is colder heads not necessarily colder sensor reading!
Q45tech wrote:Wetter water doesn't lower the coolant temperature on a Q, it raises the heat tranfer from the heads to the coolant. Thus the coolant temp sensor will show a 2-5F increase under load now the radiator may be more efficient due to the incoming air vs higher input coolant temp but this usually washes with the coolant temp going into the engine being 1-3F colder.
What you want is colder heads not necessarily colder sensor reading!
You know, I have always been meaning to discuss the heatflow involved in this with you offline.
I am not sure I come to the same conclusions as you did, which is the reason I wanna do it offline someday, as I dont think I ever rember you having been wrong on anything.So chances are I am, and hence the desire to talk offline.I wish I would ahve rembered when I was visiting in Atlanta 19-21 Dec.
Fred...
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Mayhem_J30
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palmerwmd wrote:You know, I have always been meaning to discuss the heatflow involved in this with you offline.
I am not sure I come to the same conclusions as you did, which is the reason I wanna do it offline someday, as I dont think I ever rember you having been wrong on anything.So chances are I am and hence the desirte to be offline.I wish I would ahve rembered when I was visiting in Atlanta 19-21 Dec.
Fred...
have your conversation in the engineering section or just in the infiniti general section. i'm sure it'll be interesting info either way.
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Q45tech
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They have a hard time marketing a product without alluding to something like "it lowers coolant temp" because most don't understand the PHYSICS nor the technology of how engines operate.
The product is GREAT, it does just what you want to have happen in an Aluminum engine, unfortunately most coolant systems are in POOR CONDITION and the majority are looking for cheap fixes in a bottle............not improved performance in Summer heat.
What unknowledgable person would buy a product that actually raised the coolant temp INDICATION, they would think that was bad {RIGHT} even though it lowered the coolant temp going back into the engine which is very GOOD.
All depends on where and how you measure what.
Remember the ECU lowers ignition advance [in steps every 5F] whenever the coolant temp sensor sees 194.9999F [this may not be the actual temperature at this point as [sensors/ecu interpretation of sensor resistance] will vary by +- 2-3-4F].
The point is the engine wants a VERY VERY NARROW range of correct operating temperature 176-194.99999F as measured on the output [after soaking up the heat from heads].
A new working thermostat is the most important item on the car!Luckily most fail in open [rubber seal fails allowing leaking around the valve] not allowing a correct warm up in below 90F ambient
How many seconds of WOT can the engine stand before the 194.9F threshold is reached and power is cut back slowly via reduction in ignition timing.
Many engine with bad cooling systems operate at or above this threshold in Summer [some in winter] just cruising down the road..........no reserve nothing they are already operating in the power reduction mode.
You CANNOT depend on the interior gauge to tell you much until it is almost too late because of the designed in LAG.
As you see by their graphs [Redline WW] more than half the system improvement comes from using the highest percentage of PURE water......that will not allow the heater core to freeze from AC cooling blowing on it or corrosion to start because the deionized water strips the aluminum oxide film away.
Say 75% water, 3-4% WW, and 21-25% AF.
The bulk of the cooling system temp drop comes from the lower percentage of AF not the Wetter Water.
The product is GREAT, it does just what you want to have happen in an Aluminum engine, unfortunately most coolant systems are in POOR CONDITION and the majority are looking for cheap fixes in a bottle............not improved performance in Summer heat.
What unknowledgable person would buy a product that actually raised the coolant temp INDICATION, they would think that was bad {RIGHT} even though it lowered the coolant temp going back into the engine which is very GOOD.
All depends on where and how you measure what.
Remember the ECU lowers ignition advance [in steps every 5F] whenever the coolant temp sensor sees 194.9999F [this may not be the actual temperature at this point as [sensors/ecu interpretation of sensor resistance] will vary by +- 2-3-4F].
The point is the engine wants a VERY VERY NARROW range of correct operating temperature 176-194.99999F as measured on the output [after soaking up the heat from heads].
A new working thermostat is the most important item on the car!Luckily most fail in open [rubber seal fails allowing leaking around the valve] not allowing a correct warm up in below 90F ambient
How many seconds of WOT can the engine stand before the 194.9F threshold is reached and power is cut back slowly via reduction in ignition timing.
Many engine with bad cooling systems operate at or above this threshold in Summer [some in winter] just cruising down the road..........no reserve nothing they are already operating in the power reduction mode.
You CANNOT depend on the interior gauge to tell you much until it is almost too late because of the designed in LAG.
As you see by their graphs [Redline WW] more than half the system improvement comes from using the highest percentage of PURE water......that will not allow the heater core to freeze from AC cooling blowing on it or corrosion to start because the deionized water strips the aluminum oxide film away.
Say 75% water, 3-4% WW, and 21-25% AF.
The bulk of the cooling system temp drop comes from the lower percentage of AF not the Wetter Water.
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Mayhem_J30
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Out of coincidence I stumbled across an article at a Z enthusiast site and they had evidence that a certain aftermartket radiator was dropping average coolant temps by over 23F !! That seems remarkable. I wonder though if it was being compared to an worn out 10 year old crudded up stock radiator though...hmm I'll go ask.
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Q45tech
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1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
All the NORMAL CHEAPO aftermarket new Q radiators use the exact same metal area [and thickness] except the fin count per inch varies from equal to factory to 1/3 less. the fin thickness metal gauge varies from equal to 20% thinner. The oval water passages vary by 1/3 also!Almost any new radiator will perform better than a 150k used factory unit for a short while.........the question is will it after 15,000 miles when most warranty expires.
Even my gigantic [thicker] all aluminum Griffin NASCAR model doesn't work that much better ..........we A/B against a new oem rad on the same day and found only an 9 degree improvement in OUTLET TEMPERATURE.............but 9F is significant.......running stablized in 100F at 80 mph my coolant holds 176F vs 184F factory..............that 9F means even on the hottest day with AC on I have reserve of 3-4 minutes at idle before the heat creep starts to retard timing vs 30-45 seconds on a stocker brand new.
How long does a redlight last?
A beatup/dirty partially clogged condenser adds to the suction resistance [reducing air flow].
Even my gigantic [thicker] all aluminum Griffin NASCAR model doesn't work that much better ..........we A/B against a new oem rad on the same day and found only an 9 degree improvement in OUTLET TEMPERATURE.............but 9F is significant.......running stablized in 100F at 80 mph my coolant holds 176F vs 184F factory..............that 9F means even on the hottest day with AC on I have reserve of 3-4 minutes at idle before the heat creep starts to retard timing vs 30-45 seconds on a stocker brand new.
How long does a redlight last?
A beatup/dirty partially clogged condenser adds to the suction resistance [reducing air flow].
Jerry has installed a new radiator and the spiking in temp at heavy load has decreased but it still creeps up a bit at high speed (above 85) and on an ophill grade. Jerry said the computor is throwing a code that says the fuel is running rich possibly caused by a faulty injector. I had also noticed I have been getting terrible gas mileage lately. Other than that the car seems to be running great. Any pearls of wisdom would be greatly appreciated.
crubio
crubio
It's been my experience that cooling capacity, especially when tasked with engine mods that substantially increase hp, is more dependent on airflow than radiator size and thickness. On most cars the cooling air inlets are plenty big, but there's no way for it to get out. That's why a lot of closed body race cars have that funky looking scoop in the front of the hood ala GT40 to let the air out after it passes through the radiator. The bad news is it's almost impossible for that to be improved if it's not designed into the car.
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Q45tech
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Measure the air pressure at speed under a Q hood [again with our friend the manometer [the same one [zero to 10"WC] you should have purchased to do intake and filter testing.
Think you will find little restriction [to air evacauating near the rear past the first cat and past the transmission] as long as the belly pan is in place and bolted securely at all positions.
What you will find is an extraordinary amount of restriction between the front and rear of condenser and deteriorated rubber surrounds [to keep the output of rad from flowing back].
Almost no one uses the HP of a Q for much more than 10 seconds as you will be doing over 70 mph.
A 22 mpg average says you are producing an AVERAGE of around 16-18 HP the whole time and 5-6 HP at idle to overcome system friction.
If your cooling system overheats with 20 HP [60 mph AC on] what chance do you have at 200-278HP yet brand new the Q did 15 minutes of testing in Arizona heat 100F at 150 mph with 4 aboard and AC on [5,000 rpm 250 HP] so we know an as new system can do it!
Think you will find little restriction [to air evacauating near the rear past the first cat and past the transmission] as long as the belly pan is in place and bolted securely at all positions.
What you will find is an extraordinary amount of restriction between the front and rear of condenser and deteriorated rubber surrounds [to keep the output of rad from flowing back].
Almost no one uses the HP of a Q for much more than 10 seconds as you will be doing over 70 mph.
A 22 mpg average says you are producing an AVERAGE of around 16-18 HP the whole time and 5-6 HP at idle to overcome system friction.
If your cooling system overheats with 20 HP [60 mph AC on] what chance do you have at 200-278HP yet brand new the Q did 15 minutes of testing in Arizona heat 100F at 150 mph with 4 aboard and AC on [5,000 rpm 250 HP] so we know an as new system can do it!
Ok Guys I really need you now. My 90 Q 106K has a problem with overheating slightly at heavy load. This means taxing the warmed engine at an uphill grade above 80 mph and on short steep uphill with a fully warm engine. The temp gage moves up from the 3:00 position to almost the 2:00 position but not quite. As soon as I back off or complete the grade the temp returns to normal. I drive this car every day for fairly short distances (about 40 miles per day and I drive like I'm in a Q 
. I only experience this when I drive aprox. 20 miles freeway and uphill above 85 mph. The rest of the time this car runs great (hauls **S). Jerry Tucker is having a tough time solving with this one as most systems are new and he just put in a new radiator. So far on the cooling system I have replaced, upper coolant hoses, lower coolant hoses, new clutch fan, new thermostat, New radiator hose (I bought it at NAPA autoparts and installed it myself... this could be it) new heater core (this was a fluke). New upgraded filler thing. (the coolant filler that comes off the front top that fill the coolant other than the reservoir). Also new guides, new plenium hoses, plenium cleaning, reseal heads. Jerry doesant think its the water pump.
What is causing the spike in the temp gage at heavy load?
. I only experience this when I drive aprox. 20 miles freeway and uphill above 85 mph. The rest of the time this car runs great (hauls **S). Jerry Tucker is having a tough time solving with this one as most systems are new and he just put in a new radiator. So far on the cooling system I have replaced, upper coolant hoses, lower coolant hoses, new clutch fan, new thermostat, New radiator hose (I bought it at NAPA autoparts and installed it myself... this could be it) new heater core (this was a fluke). New upgraded filler thing. (the coolant filler that comes off the front top that fill the coolant other than the reservoir). Also new guides, new plenium hoses, plenium cleaning, reseal heads. Jerry doesant think its the water pump.What is causing the spike in the temp gage at heavy load?
Woke up in the middle of the night with more ideas. Your overly rich code and bad gas mileage could be a bad oxygen sensor. Another possibility is clogged exhaust/catalytic converter, which would definitely cause high speed and load trouble. Has the car ever been in water deep enough to get up the exhaust to the cats? I think you're getting real close to solving the problem.
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Q45tech
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High load is not pulling up a hill at 80 mph even in overdrive as that might be 2666 rpm and an injector opening time of at most 5 millisecs [45% of max injection x 48% of rpm .......maybe 60-70 HP.
High load is 6,000 rpm in 2nd gear floored and locked in 2nd.
The O2 sensors can only affect the closed loop by 20% and and any extra gas will cool the cylinders making less heat.
The cats usually don't go bad [enough] but it is possible.
You need to use a Consult to measure what temp the ecu is actually seeing under these conditions.........never trust the interior gauge unless that sensor has been changed [corrosion/insulating film with age].
Measure [flat expressway] the 50 in 2nd gear locked to 80 mph WOT a few times and let me know [6.0-7.0 seconds?].......mine does an indicated 5.3 seconds [stock about 6.0 secs] but the speedo error comes into play [tire size/meter calibration]........reasonable test of engine performance from 3700-6,000 rpm..............
High load is 6,000 rpm in 2nd gear floored and locked in 2nd.
The O2 sensors can only affect the closed loop by 20% and and any extra gas will cool the cylinders making less heat.
The cats usually don't go bad [enough] but it is possible.
You need to use a Consult to measure what temp the ecu is actually seeing under these conditions.........never trust the interior gauge unless that sensor has been changed [corrosion/insulating film with age].
Measure [flat expressway] the 50 in 2nd gear locked to 80 mph WOT a few times and let me know [6.0-7.0 seconds?].......mine does an indicated 5.3 seconds [stock about 6.0 secs] but the speedo error comes into play [tire size/meter calibration]........reasonable test of engine performance from 3700-6,000 rpm..............
Hey guys, As far as I know the previous owner had replaced the radiator at around 75,000. I purchased the car at 90,000. I didant expect to replace the radiator this soon but as for what whas done to the car before I bought it you can never be 100% sure, I just upgrade and replace when necessarry. I think this is a pretty good radiator as this is the replacement radiator Jerry Tucker uses on the Q's he services. The car runs great. Now if I can only find a 93 TCU for a reasonable price...
crubio
crubio
Well folks, I am having exactly the same problem as crubio, intermittent overheating problem at 85+ or while cruising below 45 on a hot day. Temperature stabilizes once I climb down/up to around 70MPH. I've changed thermostat, but do suspect the radiator. So like Crubio I'll try changing it. My Q45a has 168,000+ miles and has been to the UK and back. Its not even sold in the UK so, its a miracle that they were able to maintain it for 4 years.
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Q451990
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I vaguely remember Q45Tech mentioning a Q from somewhere in Europe coming in to T3 at some point and needing some remedial help since it had been serviced without having the parts available. Have you taken it there yet? I'd replace the radiator just to eliminate it... overheating can be disasterous.
Heath
Heath