Datsun 1jz overheating!

[Tim]

hey guys,
got my 1jz in my datsun 260z running and it starts to over heat when it idles for a while. I found out that coolent is not flowing through the radiator when I look through the top of the radiator. The upper rad hose is hot and the lower is cool. Seems the thermostat is not opening. I ran this motor before and it was fine, and it has a fairly new thermostat in it. The only difference now is that I am running a mk4 water pump with no ac or power steering. The only other difference is that I have a single turbo, and i am looping the water outlet line next to the thermostat housing up to the water outlet next to the upper radiator hose, which I think might be my problem. should I just cap those lines off, because thats how I had it before and I never had a problem.

 

[RacerXJ220]

Did you measure how much coolant you put in to ensure you have filled it to capacity?

What is your engine temperature before it overheats? Is it at the thermostat thresh hold?

 

[tsuper92]

looping the upper hose to the lower will not cause the overheating.you can pull those little nipple's out and tap them with 1/8th" pipe thread without any drilling.just make sure not to run the tap to deep,because it is a tappered thread.
after deleting the ac and power steering,do you have the waterpump spinning in the right direction?

 

[Torque]

I too think that it's a water pump issue.

 

[Evilempire1.3JZ-GTE]

The water pump will not pump properly unless you have the belt on tight I think thats most likely your issue I deleted the AC then went with a belt that landed the tensioner in the middle mark you almost want it at max at new so when it settels out and streches a little there is no slack in it.

If your belt tension is not the issue then your problem is you didnt burp the air out of the system right I used a TRD thermastat with the little nipple bypass cut off that lowers the temps a little bit. EGT can be high, unproper water to coolant ratio can be an issue, electric fan not working at the right time, bad water pump like water leaking out of the weap hole, bad radiator cap to small of a radiator and to large HP in upgrades. electric radiator fan not hooked up right etc.

Water will normaly not flow with the radiator cap off because the thermastat works off from pressure your coolant system wont have pressure if there is air in the line or the radiator cap is off because the spring doesnt actuate by heat but by the pressure of water in the system after it reaches a certain temp!

Other overheating issues can be BHG rare but can happen to any engine especially if over heated with an aluminum head.

But due to the fact you say one line is boiling hot and the other is cold it sounds like it could be a circulation issue also like pump or air in the system. Also make sure you put the thermastat in the right way and not backwards.

 

[Evilempire1.3JZ-GTE]

One other thing I almost forgot
Dont tap your turbo coolant line at all!
Just pull out the two 3/8" nipples out of the water neck with vice grips try to avoid twisting to much to bore it out.

Then get aluminum -6 AN hardline or 3/8"OD aluminum hard line then add the couplers tothe turbo side and just plug the new aluminum line directly in there, before installing coat it with a thin coat of sealant around the OD of the line it will seal in like factory, because if you tap & thread out the water neck the water coupler usually ends up with a more restrictive inner diameter then the factory coolant hard line.

Also I marked the old nipples before pulling them out because when you tap the new water lines into the water neck to seat them it helps to know when to stop hitting the line so its seated all the way in. I did my cooland lines for my turbo all hardline like factory mostly does.

The nipples I used was the rear engine one it seamed to be more of a streight line from the turbo for the return line also the one at the bottom of the water neck pointed to close into the alternator.
Pick tany of the two water feed lines off the top water neck and use the one you perfer.

 

[Poodles]

No, the t-stat doesn't operate from pressure, it's temp.

 

[dslocal]

Water will normaly not flow with the radiator cap off because the thermastat works off from pressure your coolant system wont have pressure if there is air in the line or the radiator cap is off because the spring doesnt actuate by heat but by the pressure of water in the system after it reaches a certain temp!

I also disagree. If you take your t-stat and put it in a pot of water on the stove you can use a thermometer to watch what temp it opens at. If it doesn't open get a new one

 

[Tim]

im not stupid, Im a technician for Nissan, so I ruled out the obvious (waterpump, belt, ect...). I took the thermostat out and it is seized. it has less then 500 miles on it, but it has been sitiing for over 2 years without being run. Ordered a new one today! Not easy to get the thermostat housing out with the drewgo header! Gotta use some brute force!!

 

[dslocal]

im not stupid, Im a technician for Nissan

This statement kinda contradicts itself:icon_razz

But isn't the thermostat something pretty obvious to check, in my shop we get cars with them bad all the time.
Just givin you crap don't take me seriously:biglaugh:

 

[wiseco7mgt]

He can't be too silly, he used a 1j over a Rb motor..

 

[Dylan JZ]

He can't be too silly, he used a 1j over a Rb motor..

haha very true..

 

[giterboosted]

off topic...... pics of car?