I must preface this by saying it is 106 degrees as per q45. After driving for 1 hour in stop and go traffic my car began to increase its' temp. the temperature gauge is running about 20% warmer than normal. Inthat, while it would ordinarily be at 3 O'clock. Now it is at about 2 O'clock. When I start driving it will decrease to a little above normal. But if I turn my car off and walk away. when I return to my car about 10 minutes later it will be hot again. Almost at the top of the normal range. When I begin to drive it will return to normal again. I wonder whats going on? Fluid has been changed and is normal level. Also no weird noises and car is performing well as usual.

Make sure the electric fan in front of the radiator is working and if it is change the thermostat. If that doesn't do it you need a new radiator.

Change the Tstat first, my guess is your rad is clogged... but replace the Tstat first... might make sense that it got stuck partially open.. Definitely deal with it now before it gets worse!

I will change the thermostat anyway, but what can I do about a clogged radiator. Next, how does this closed system get debris in it?

Jehangir wrote:1. I will change the thermostat anyway, 2. but what can I do about a clogged radiator. 3. Next, how does this closed system get debris in it?

1. Good2. You gotta replace it..... 3. From the system corroding, basically from not replacing the coolant often enough

Nasty Nasty stuff came out of my radiator. I flushed it and replaced the thermostat. After driving it for 1/2 hour the car remains at the correct temperature. Thanks guys!

Another thought for you... does your car still have the road shield a/k/a "belly pan" covering the bottom of the engine bay? I removed the one on Q1 for a day or so and noticed that a lot of hot air blows directly down and bounces off of the pavement in front of the car. I would think that in stopped traffic you could set up a cycle in that that the already hot air coming from behind the radiator could be pulled back in front of the radiator and cause an overheating issue that way by feeding it hot air that keeps getting hotter...

Heath

Thats an interesting thought. My belly pan was just removed about a week ago. But I thought hot air raises. Still the main engine fan my push the air down. Hmmmm

No under engine tray baffle, no effective flow through the radiator.

Look at it installed. Fan pushed air spills around rather than through the radiator, especially at low speed. Foam air blocks at each side in front of radiator critical also for the same reason.

*flame suit engaged*

I highly doubt that little piece of plastic is causing your car to overheat.. IT may make it run warmer at idle in traffic (even then, id still question if really has any impact)... but it isnt going tomake the difference between being normal and hot.. That can only mean the radiator or something like that..

I bet that at 100F that with/without the belly pan you could only measure the difference with a consult, and it would only be a few degrees difference.....

People tend to overanalyze the function of these things.. More likely why the belly pan is there is to protect the under part of the engine, and things like the tranny cooler lines.

Wes, have you ever looked at it? It is there for the air flow.

Acheiving a low CD was one of the primary goals of the Nissan design team. Getting the air to flow properly through the engine compartment is intrumental to proper cooling with the marginally sized cooling system.

Think the foam blocks are there just to keep the radiator from hitting the condenser?

Take some physics (surely your high school offers an intoductory course?) and you will be better able to judge the engineers' design intent.

Wes... stand with your feet under the nose of an idling Q without the belly pan... There is a LOT of hot air hitting the pavement. I agree that it wouldn't be a big deal in normal conditions - but a 100+F every ounce of cooler can be critical between hot and dangerous. Sucking reheated air through the radiator again and again can only have a cascading effect.

Heath

Well I finally picked up my 94 Q last nite, drove 300 miles to get it, but so far it seems worth it. But I got a few hickups already.

This is the 1st time I ever layed my hands on a VH45DE, I used to work at Nissan as a tech, but we didn't service anything like this before. So my mechanical knowledge is good, but I aint no VH45 king yet.

I changed what it looked like original spark plugs today to some NGK G-Power Platinums, changed fuel filter, and oil change, and throttle body +TCS cleaning. After looking through my MINI FSM I couldn't find where the PCV valve sits, as I wanted to tackle it- does it sit under the intake somewhere ? I have a leak from "blow by hose" and some moron has tried to put electrical tape around that vacuum hose to stop the vacuum leak.

Engine tends to run really smooth at idle, but it has no balls. It seems to be really smooth when accelerarting lightly, but give it some throttle and it just doesn't wanna go, feels like its strained. I mean turning off the TCS and flooring it in 1st gear will not do anything, and acceleration is on par with maybe a automatic VG30E powered 3rd gen Maxima, which is NOT what I was looking for. No check engine light, but I am going to hook up a Consult to it tomorrow cause I am kinda pissed off with the power.

Another thing is, the engine looks like its overheating too. Its got a new radiator, seems like the OEM one blew up about a year ago. Current radiator looks fairly new and its aftermarket.

I have not looked at the FSM, nor did I look around the engine, but where is the thermostat located ? do I have to pull the intake ? Does anyone have a part # list of all the gaskets and hoses to be repleaced that sit under the intake ? I would like to repleace my valve cover gaskets while having the intake off- hopefully my headgaskets are good or I will need more part #s and know someone good over at Infiniti to give me a decent deal on parts.

I thought bout making a new thread bout this, but this one sounded similar to my problem + some more.

Q451990 wrote:Wes... stand with your feet under the nose of an idling Q without the belly pan... There is a LOT of hot air hitting the pavement. I agree that it wouldn't be a big deal in normal conditions - but a 100+F every ounce of cooler can be critical between hot and dangerous. Sucking reheated air through the radiator again and again can only have a cascading effect.

Heath

I know, I realize this... I just have a hard time that it would make the difference between overheating and running cool.... He says it increased by 20% or so, I just have a hard time that it would make any more difference than 5%..... I dont doubt that it may be making some difference, but is it that much? *I* dont think so.... Then again i could be young, ignorant, and naive

BlackBirdVQ wrote:Well I finally picked up my 94 Q last nite, drove 300 miles to get it, but so far it seems worth it. But I got a few hickups already.

This is the 1st time I ever layed my hands on a VH45DE, I used to work at Nissan as a tech, but we didn't service anything like this before. So my mechanical knowledge is good, but I aint no VH45 king yet.

I changed what it looked like original spark plugs today to some NGK G-Power Platinums, changed fuel filter, and oil change, and throttle body +TCS cleaning. After looking through my MINI FSM I couldn't find where the PCV valve sits, as I wanted to tackle it- does it sit under the intake somewhere ? I have a leak from "blow by hose" and some moron has tried to put electrical tape around that vacuum hose to stop the vacuum leak.

Engine tends to run really smooth at idle, but it has no balls. It seems to be really smooth when accelerarting lightly, but give it some throttle and it just doesn't wanna go, feels like its strained. I mean turning off the TCS and flooring it in 1st gear will not do anything, and acceleration is on par with maybe a automatic VG30E powered 3rd gen Maxima, which is NOT what I was looking for. No check engine light, but I am going to hook up a Consult to it tomorrow cause I am kinda pissed off with the power.

Another thing is, the engine looks like its overheating too. Its got a new radiator, seems like the OEM one blew up about a year ago. Current radiator looks fairly new and its aftermarket.

I have not looked at the FSM, nor did I look around the engine, but where is the thermostat located ? do I have to pull the intake ? Does anyone have a part # list of all the gaskets and hoses to be repleaced that sit under the intake ? I would like to repleace my valve cover gaskets while having the intake off- hopefully my headgaskets are good or I will need more part #s and know someone good over at Infiniti to give me a decent deal on parts.

I thought bout making a new thread bout this, but this one sounded similar to my problem + some more.

Welcome to the forums congrats on pikcing up your 94Q!!!

First thing the PCV valve is right here.....



You take off that little plastic piece in the center-front of the plenum (thathas the infiniti sticker on it) and the PCV valve is sticking in the radiator filler neck...

possible you have some MAF or knock sensor related issues... Might check the codes for starters...

The thermostat housing can be seen easily once removing said plastic cladding peice.. The lower radiator hose connects iwth a metal hose and then elbows into the T stat housing.....

http://infiniti.home.insightbb...s.htm

Theres a list of the crap you need to replace

Thanx ALOT for the info. It was getting really late last nite when I was doing plugs and other stuff on the Q at work. We close the dealership at 9PM and I was there till like 8 working on the car. I thought bout taking off the shield that sits between the 2 cylinder heads that you talk about but just didn't have the time.

Tomorrow I am planing on putting new pads on ( sensor says they are worn and they are, plus rotors pulsate) and cutting the front rotors if I still can. I wanna put in a new T-stat as it apears the engine temp goes up n down and if I keep the heat on MAX with fan on full speed it will not move. I am not sure if its loosing coolant but I will check tomorrow. I need to properly bleed the cooling system cause I'm sure it has a ton of air in it. Like I mentioned it has a new waterpump, radiator hoses and radiator, but T-stat is still original. I got my fingers crossed that I don't need to do head gaskets on this thing.

I got a vacuum leak that some idiot tried to fix by putting electrical tape over the PVC breather hose- hose FSM specifies to pinch when testing for vacuum leaks. I will try run a hose differently without removing the intake for now.

According to the maintenace records both knock sensors where repleaced by the dealer not too long ago. Driving the car I can feel it hesitating at higher engine speeds, and sometimes the trans shifts all wrong due to some sensor just not cooperating. I am going to hook up the Consult to it tomorrow and check what I got going on in the ECU.

Other than a few minor issues the car is pretty good. Previous owner kept it up pretty good (loved sunflower seeds it looks like ! tons of them where unde r the seats) as far as maintenance goes.

Well a week of driving and today car overheated and leaked out coolant from the radiator ( I repleaced the T-stat, hoses, and it had a aftermarket OE radiator installed by the previous owner) giving me the impression that there is some damage to the head gaskets ( Acura Legends tend to do the same). So I am going to tear the heads off the motor this week and see whats going on. I will take some pics of the VH45 with no heads on it.

Edit- I will check the radiator out thou, before I do the head gaskets- I haven't seen a newer Nissan motor ever blow a head gasket.

Can't say that I've ever heard of a head gasket failure on a Q in 7+ years of pretty active internet forum membership (Yahoo, then NICO). Not saying it's impossible, but I would sure pressure test the heck out of it first...

Heath

Q451990 wrote:Can't say that I've ever heard of a head gasket failure on a Q in 7+ years of pretty active internet forum membership (Yahoo, then NICO). Not saying it's impossible, but I would sure pressure test the heck out of it first...

Heath

Remeber that he did say it overheated, and the previous owner overheated it a couple times as well!!!

If it overheated, all bets are off.

Well I am pretty hardcore Nissan enthousiast myself and havent seen a headgasket failure on a Nissan since the 80s ! I decided to drive the Q tonite to see if she would overheat, bout 3 miles of stop n go driving the temp gauge sat at COLD still, then it started to slowly get up to temp. I got over to my friends house and a mile from his house the temp started going up- heater didn't work even ! Well I let her cool off and got some warm water to pour into the engine and here is what I found...

Year old aftermarket radiator (has approx 3K miles on it, since the car wasn't driven much) has cracked at the lower end tank and pissed all the coolant out. When I was adding water into the engine it was just POURING out the bottom right corner right by the drain plug area.

Tomorrow I am going to call Moldine Radiators and see if I can get me a new aftermarket life time warranty radiator from them. I have had good luck with them on Hondas and even have one in my Legend now with no problems. I need to get the car runing as my fiancee wants to drive the Q while I bling her Legend out for her.

I will keep ya posted, I was already going to order new head gaskets tomorrow and tear the heads off this week- but the radiator needs to be fixed before I can asses any other damage.