Overheating?

[jacob80]

Hey guys,

 

Well I've just put a new head gasket on the car, new oil and new coolant, and while sitting and idling for about ten minutes, the temperatures climbed to about 219 degrees. I shut the car down, I was not about to let it get any hotter. Keep in mind that I was not running a fan, which very well may be the reason, but is this normal without a fan running? Right now, its not kicking on for whatever reason (working on it), but I'm not about to warp my head. Thanks guys!

[stravi757]

Well if the car isn't moving and you don't have a fan, then you really don't have anything cooling your water. If Im at a stop light on my bike for a couple minutes the water temp goes way up really quickly. Just put a Fan back on or maybe an E-fan. problem should go away.

[jacob80]

Okay, cool. I have a fan installed, just having power issues. The only reason I ask is because I replaced the head gasket because of overheating issues, so I pray it isn't happening again.

[stravi757]

Well why did it over heat before? Did you figure out why. Was it because of a bad thermostat, water pump, broken hose, bad radiator ect...

[ktm]

If the car is not moving then you have no means of passing air through the radiator. It is this movement of air that cools the coolant, not simply having a radiator in-place.

[nosebleedZ]

Stravi & KTM are on the money, man. Unless you like wrenching more than driving, do the following w/ new head job, especially on an L engine:

1)flush block/ head w/ descaler & pressurized water

2) change to new or colder T-stat (I use a 150*, stock is 180*)

3) A fan is a must! Stock is adequate, but the best IMO is a hi-flow electric(s) w/ temp sensor to turn it on, which is great in traffic on Z's.

4) Remove any & all debris from both sides of the radiator

5)Always do a new water pump with a new head, it's 25 bucks!

6)Replace all hoses that carry coolant & rad cap...period.

7)Fill with 50/50 coolant & distilled water if below the Mason/Dixon Line

8) Have rad boiled out & fins straightened if not a new one

9)Adjust water pump belt or replace & adjust correctly

10) Ensure ignition timing is not too advanced

 

If it overheats then, only can be the block is in dire need of hot tanking (think of Draino in a 50 yr. old cast iron sewer pipe)- flow sucks, head or gasket is still not sealing, belly pan has been removed allowing airflow to the rad to go around it, or your turbo is being spun all the time (like most of us on this site), remember power & heat are same thing...LOL. Hope this helps!

[ozconnection]

....... remember power & heat are same thing...LOL. Hope this helps!

 

 

 

You run a 150 degree thermostat though? Any reason?

[nosebleedZ]

Yep, with the tendency of the L-series to run warm, dropping to a tropical thermostat will lower the overall operating temp of the motor because the thermostat will open about 20% sooner to be cooled again. Since I throw alot of heat at the engine (20-25psi boost), this further reduces the tendency to detonate. You just have to tune the ECU for the lower temps or it will buck & misfire when warmed up. If you look at many of the aftermarket tuning kits available, a colder thermostat is usually part of the overall tuning package- see hypertech, bullydog, venom, etc. Yes, emissions will be higher in states that have testing because a cooler engine requires more fuel to perform well. The reason most modern vehicles have normal operating temperatures from 180- 210F is because of emission requirements. Datsuns came with this thermostat or the 160* version OE in South America, Africa, etc. in the early 70's where emission compliance was not paramount. Napa still sells the tropical version here in the states.

[jacob80]

Block was hot tanked when rebuilt, so that can't be the issue. I took your advice and ordered a 160 thermostat and water pump. Were also running an MSA aluminum radiator which is fairrly new but we were using it on our old L24 that was pretty nasty, so perhaps I should clean it out somehow, just to be sure. Any other suggestions? Am I experiencing anything out of the ordinary consdering I was running it with no fan? Thanks guys!

[Tony D]

Yep, with the tendency of the L-series to run warm, dropping to a tropical thermostat will lower the overall operating temp of the motor because the thermostat will open about 20% sooner to be cooled again. ... Datsuns came with this thermostat or the 160* version OE in South America, Africa, etc. in the early 70's where emission compliance was not paramount. Napa still sells the tropical version here in the states.

 

The Nissan Thermostat came in 72C, 82C, and 90C versions. There was no '150F' thermostat available, the Tropical Thermostat was a 72C version.

 

That is roughly equivalent to 160F. There was no '62C' thermostat available.

 

That number is really low, and I'm a proponent of 160F thermostats. The oil temperature is what you really need to regulate and the OEM's do that indirectly through water temperature.

 

I just want to make sure this is clarified. The tropical thermostat---the lowest recommended and installed in vehicles from the factory by Nissan is 72C, or 162F. Nothing lower, I have the part numbers to support this, and it's in the fiche as well for anybody else to verify on their own.

 

I have never seen a 150F thermostat for a Nissan Roadgoing Vehicle. Anywhere.

[stravi757]

I think he meant 160 not 150, he wrote 160 in his second post.

[Tony D]

It says 'this thermostat or the 160'---which sounds as he is discussing two different thermal values. Tropical/72C/160F is the same, Normal/82C/180F is the same, Frigid/90C/190(5)F is the same. Those are the available options.

 

There was nothing below 160 as a factory offering in a roadgoing passenger vehicle.

 

If you are overheating using a 160 thermostat, likely there are other issues that need to be addressed. A 150 is sludge forming territory in about anywhere, including the tropics, there will not be adequate lubricity in the oil even in the hottest part of the head. You will barely make 180 in the hot parts of the thread or throw-off on heavily loaded areas of the bearings. Like I said, I'm a proponent of 160F thermostats, but advocating the use of a 150F is getting to the band-aid stage for another issue, compounded by the fact it will not allow proper oil temperatures. There is a reason Nissan stopped at 160F for passenger vehicles---Oil Temperature lower limits even in the tropics. Unless you're blasting across Saudi Arabia in the middle of summer a 150 is going to cause long-term issues. And even in that case, you will be running a thermostat lower than ambient temperature available for cooling... let's not go into that direction shall we?

[nosebleedZ]

Tony, you are probably correct if you researched it that heavily. I was going from Napa's info from when I bought it several years ago. Doing an "off-the car test "at that time for experimentation sake, & like jacob, I was having heating issues, the T-Stat I put in my car was full open position in a pan of hot water registering 150-ish with a infrared heat gun. I would have to have Napa check what they offer still or if it was a 160*, I was only intending on nudging jacob in the right direction, and not trying to give him irrefutable information on nissan OE thermostats. As for the sludging, yes cooler oil can have less lubricity & sludge if not driven hard enough to thin the oil & its given additives, but this is also relative to oil viscosity, type (syn or con), & thermal expansion properties of the engine bearings relative to adequate oil clearance requirements. Also, during hard driving the engine will exceed the T-Stat baseline temp for short periods depending on ambient temp & boost, in my case. This probably relates little to jacob's overheating issue (unless he's using straight 50 wt), but informative info none-the-less! Jacob, your not experiencing anything out of the ordinary without a fan, like Stravi said. It's just a wiser thing to ensure all parts of the cooling system are up to snuff with a new head, to give it maximum life & that no other symptoms are hidden due to the fan being on vacation. Happy wrenchin'!

[jc052685]

Stravi & KTM are on the money, man. Unless you like wrenching more than driving, do the following w/ new head job, especially on an L engine:

1)flush block/ head w/ descaler & pressurized water

2) change to new or colder T-stat (I use a 150*, stock is 180*)

3) A fan is a must! Stock is adequate, but the best IMO is a hi-flow electric(s) w/ temp sensor to turn it on, which is great in traffic on Z's.

4) Remove any & all debris from both sides of the radiator

5)Always do a new water pump with a new head, it's 25 bucks!

6)Replace all hoses that carry coolant & rad cap...period.

7)Fill with 50/50 coolant & distilled water if below the Mason/Dixon Line

8) Have rad boiled out & fins straightened if not a new one

9)Adjust water pump belt or replace & adjust correctly

10) Ensure ignition timing is not too advanced

 

If it overheats then, only can be the block is in dire need of hot tanking (think of Draino in a 50 yr. old cast iron sewer pipe)- flow sucks, head or gasket is still not sealing, belly pan has been removed allowing airflow to the rad to go around it, or your turbo is being spun all the time (like most of us on this site), remember power & heat are same thing...LOL. Hope this helps!

 

 

You seriously think an electric fan will flow more than the OEM fan? I dont think there is enough alternator on the car to run enough fans to flow as much as the OEM fan. I would bet that thing moves 5000-7000 cfm, maybe more. Especialy with the shroud.....

[jacob80]

Well good mews, I repaired my fan and the car was staying nice and cool! Currently, we have a 180 thermostat in the car, so it sounds like that's what I will be using.

[ktm]

You seriously think an electric fan will flow more than the OEM fan? I dont think there is enough alternator on the car to run enough fans to flow as much as the OEM fan. I would bet that thing moves 5000-7000 cfm, maybe more. Especialy with the shroud.....

 

Timz switched to a stock fan on his car for this exact reason.

[ozconnection]

Fan AND shroud.....

 

A fan (any fan) by itself if not the whole answer and a 16 inch electric fan may perform better fitted to a radiator without the shroud. (Closer contact to the radiator may provide a better pull/push of air through the fins it covers.)

 

My setup is now a 16 inch electric fan contained within a factory shroud. It's had no problem holding the temperature of my engine stable in traffic, with the aircon on and on hot summer days!

 

I'm very happy with my mod!

[Tony D]

I tried a single fan at one time, and the flow simply wasn't near enough in SoCal...

 

I put twin 10" fans on there with a rating of 5000cfm each. By using an electronic fan controller set to engage the fans at 10-15F above where the car stabilized at temperature on a 110F day driving down the road at 35mph in fifth gear (which was near 160F, meaning I set 185F for fan turn-on) I would be able to see distinct temperatures on the car.

 

At 35mph, the car ran around 170F.

At 55mph, the car ran just above thermostat setting at 165-170F.

At 60mph, the car ran at thermostat setting EXACTLY. Dead nuts 160F. This means around 10,000 CFM is theoretically passing through the 1'X2' radiator opening...

Curiously the car ran cooler between 60 and 80mph than it did at speeds slower! I did not see temperatures above that point (180F) until I was continually running 85+mph. This is on a 110F day. Do the C conversions, this is a THREE CORE radiator I was using on a turbocharged 240Z with approx 325HP at the rear wheels.

 

In stop -n- go coming off the freeway, I would see the temperatures rise. My temperature would rise to 180-190F and the fanS would turn on, I could see the temperature drop to the shutoff point (around 170) and then rise again. This is what it will do. It is set at a point not wo exceed 190F in traffic, and with those twin fans IT NEVER DID.

 

Did it run hotter than on the freeway? Yes, by 10 degrees, and BY MY DESIGN. Stop-n-Go is worse on the car than freeway driving, run the temperature a bit hotter to keep the oil clean. It also lets me know if the fans fail BEFORE the temperature gets to a point where damage is done. I can tell exactly where on the gauge my car should run wether it's on the freeway or not.

 

Setting them this way also has insured I NEVER have the fans running on the freeway---this is something you shouldn't need, and don't want to do anyway.

 

It's like clockwork, I pull off the freeway, I watch the temp rise...my fan kicks on just as it goes slightly to the right of center by about a needle-width, and the fans turn off about the same orientation to the left of center. Normal freeway position is slightly to the left of that point. I can watch it cycle back and forth right at the centerline as I hear the fans come on and off.

 

If your fan comes on, and your temperature doesn't start dropping: YOU NEED MORE FAN! It is that simple. Fancy fans, shrouded fans, expensive fans, if this happens your fan is too small. You need to have a MINIMUM of 5000cfm through the radiator (that is 30 mph...) and as you can see from above, the car runs hotter at 35 than it does at 60, so for FULL cooling you need 10 KCFM. I don't care what the manufacturer says, how much horsepower they SAY they can cool with this fan or that... I followed this recommendation which said a single 14" could cool my car ("Recommended for Datsun 240Z, V8's to 350HP"...) and it would runaway in traffic. Could not keep the car cool.

 

Doubled the fans up to twin 10" and CFM capacity of 11,000 CFM to coincide with my calculations of capacity and my overheating in traffic problems went away. Can you get away with a smaller fan? Sure, but it will take longer cycling of the fan, if not constant running while at idle---if you have that, why change from a belt driven one that cools the car just fine as it is???

 

I DID cool with a single fan at one time. I had a WONDERFUL silend shrouded fan from a refrigeration unit off a Hino Diesel REEFER Container. Draw was like 30A when it was running, and MAN it cooled great. But it was slightly bulky, and it didn't look that great. It's hanging in my shed, and I use it whenever I have to get a car home that I suspect the fan is bad, or doesn't have one...

 

ONE LAST IMPORTANT NOTE:

No matter WHAT I tried, if I had the fan coming on at 190F or higher, IT WAS TOO LATE and the fan would not cool it down. That means the 'set temperature switches' simply won't work for me. I got one which was adjustable, and prefer the electronic one to the capillary microswitch type because of failure problems I have had with that particular setup. I have not had luck actuating the fan much later than 180F. Earlier seems to head off something happening inside the engine and keeps it from becoming a problem. (Class, who was paying attention, what could be happening once water temperature reaches 180F+, and you have low cooling water flow and no pressure from the pump turning at higher speeds?)

[ozconnection]

Cavitation!!

[ozconnection]

Tony, where do you get to drive, in SoCal, at speeds in excess of 85 mph continuously to find out that your cooling system isn't keeping up?

 

Man, I'll only touch those speeds for a moment as I do my G-tech testing runs. Other than that, its more like up to 70 mph continuously....no more...too risky