Ok so a few questions. I removed my heater core, and ever extra coolant line etc... So my cooling path now goes Rad, thermostat, heads, rear coolant pipe, back to rad. I do not have the crossover tubes, bypass, oil cooler, throttle body lines etc. I am having some issues with the nismo t-stat. I have used the spill free funnel, and it feels like the t-stat is open because the lower hose is hot to touch. Then I go out for a small cruise and the car will opperate in the 180's -200 area until I get on the highway it shoots up. Which is leading me to believe that the is still air in the system.

According to the service manual flow chart, I should not be creating a flow problem by deleting any of the items I have, I just wanted to get some opinions. I am probably going to take it to, pull the t-stat and dremel off the little pin on so that hot water can bypass if air gets trapped.

Last resort a friend has a machine to draw vac through the cooling system to ensure there is no air, just trying not to trailer the car to him if I can figure it out on my own.

Danny

I am not sure

 

it is tough looking at the cooling diagram but you wonder if eliminating the input into the thermostat from the oil cooler/warmer and the outlet to the heater on the side of the engine affect the flow of coolant past the thermostat to allow it to open properly

 

I have also eleminated most of the extra coolant lines looking at the cooling diagram but I still have my heater core. I haven't had any issues but I had fears that the T-stat wouldn't open as well when eliminating the bypass line. However i use evans coolant and a zero pressure rad cap so I don't think air can get trapped with the pressure less cap.

Before I used Evans and a pressureless cap I used the no spill funnel and let the car run for a long time I did this several times and even had a friend rev the car a fair bit and that seemed to bring air bubbles everytime he reved it.

Not sure if that helps or not.

 

I ran the car for almost 1.5 years with everything removed except the heater core, so I am fairly confident that the flow is still correct. I do think that there could still be air trapped behind the T-stat, which is why I am considering dremeling the piece off the Nismo stat to allow hot water from the other side of the t-stat, similar to the oil warmer giving hot water to the t-stat.

 

In mine I have heater core bypassed (inlet and outlet pipes for heater core have rubber caps), dont have TB lines, oil "cooler" lines, nothing, just radiator, however i still have the bypass line. I havent had a single problem in two years. My thinking is, if you dont have the bypass line, when tstat is closed, how would the coolant flow? The pump would just be pushing it but no where to go since everything is closed.

 

That was kind of my thinking as well, this is why I wanted to delete the small nipple inside the nismo stat. This would be similar to drilling a small hole in a regular t-stat.

 

I also thought the same thing about the bypass line after I removed it but my T-stat opens still I was thinking if it didn't open I was going to modify the T-stat as well mine opens but I am not sure why or how. Danny is the only change you made this time was eliminating the heater core?

I thought of drilling a couple small holes in the T-stat to allow some coolant to pass through.

 

i agree with the bypass line being gone causing problems with the t stat opening. The hot coolant has no way of getting behind the t-stat to heat the spring and thus open it.

So that makes me think that for some reason when the car is cold you would just build up a lot of pressure since there is no movement of coolant.

if you went that extreme to remove others i'm going to think this isn't a daily driver so you could just gut the thermostat. It would bleed really easy and work properly that way.

 

with regard to getting flow to the t-stat, isn't the oil cooler/warmer line delete more of the issue than the bypass line? IIRC, the bypass connects a little further back on the block, but the oil cooler/warmer line connects at the t-stat. danny, when dave & I talked about this last year he suggested keeping the oil cooler line (get rid of cooler though) to maintain flow to the t-stat.

 

I'm building an HR motor & the hard water piping manifold on the left side of the engine don't fit with my design, so I built another manifold for it now feeding under the motor. there are 3 inlets at this water manifold, from memory I think one is the small return that comes from the oil cooler, I'm using that circuit instead to cool the turbos, one is from the heater core, & one seems to just be a bypass from the tube that connects to the back of the heads which is being fed from the radiator. I've looked at the FSM & studied it, but even that doesn't fully explain the cooling circuit to me, so I've checked out how these feeds relate to the water pump orifice & it seems to me that the engine needs to pull bypass at this manifold for the thermostat to function as designed, weather it's from the oil cooler, heater core or just the back of the heads I think it needs this feed.

if you blocked off everything but the heater core before, then you still had a feed at this point. did you now just block off that feed? I would say to try just running a bypass into this port from the rear head water manifold rather than just blocking it off, I was afraid to even reduce flow to this manifold let alone blocking it off from any flow.

 

the 2 pipes that come into the side of the block empty directly into the space behind the tstat. 1 front the heater core and the other from the oil cooler. The bypass line is what attaches to the front of the tstat but all 3 of those flow coolant to the tstat opening.

 

i think we must be using different terminology (or we have very different plumbing ). the oil cooler circuit goes from the bottom of the passenger side hard pipe, down to the cooler, then up to the port on the front of the thermostat. the bypass line goes from the top of the passenger side hard pipe, in front of the timing cover, and ties into the block (along with the return from the heater core) at the hard pipe on the side of the block. i agree with you that all three provide some flow to the back of the t-stat, but the oil cooler/warmer circuit is more direct.

 

I do agree with you guys, I have ran with no bypass line or oil cooler line for some time. It was recent delete of the heater lines that started the issue. I have a couple ideas before I drill the t-stat. I think I just have an air pocket behind the t-stat and with no burp valve, or heater to help me get rid of the air. It is stuck in the block.

This weekend I think I am going to trailer it to my buddys shop to vac bleed the coolant and see what happens.

 

instead of drilling the t stat you can just run a feed to it, if you don't want to see any rubber lines then you can do this with AN braided & even run it down under the engine like I did here. this is the HR setup, but the DE is about the same, just 2 feeds instead of 3, even one should be fine though really, I think it def needs flow in from this point, looking at the casting of the block where the t stat sits the t stat will not function correctly without this flow I think

 

I actually agree with you, I was just looking at one of the DE heads.

 

I dunno I have no bypasses etc anymore and have no cooling issues. So I can tell ya, that shouldn't be your problem

 

ah, i got them backwards

 

Ya but after looking at the drive head, with both the heater and bypass removed it looks like it may be creating the issue.

 

A looking at the diagram remove both lines would likely cause a problem with the T-stat getting coolant flow. I wonder if drilling 2-4 small holes in the t-stat would give it some flow and allow it open


Or as above add a fitting to the block off plate you made where the two hard lines went in then maybe bring a line from the cooling log at the rear of the engine to keep things looking clean. That plate is a b1tch to get off with the engine in the car if your turbos have heat shields anyway I had to get mine off because my one block off had a pin hole.

 

I was thinking the same thing Gord.