is this a common coolant leak on rb25?

[ANVIL]

Above water pump almost where the intake manifold / head / block meet.

Any guesses on what it is and how to fix it?

Ive been chasing an annoying coolant problem, details in this thread:

high-operating-coolant-temps-s13-long-n ... 92346.html

Im wondering if this may have some kind of effect on my problem. I haven't gotten around to installing the coolant breather tank yet mainly because im unsure where to put the hose thats supposed to go to a bleeder valve because freddy doesnt have a bleeder valve and im not confident on drilling to make one myself....

Any help or input would be appreciated!

[Yellow4g63]

You can add a die to the coolant and then check with a UV light. Kinda hard to tell from the pic but it looks like it's around the water pump.

[ANVIL]

I believe I found the culprit. After driving home from work a block away coolant temp shot up and steam coming from the engine bay. Pop the hood to find this



Inlet on my isis manifold popped off! Im hoping it was a small leak and led to that and nothing else....

So how do I get this pipe to stay in?!? Obviously the sealant I used didn't work out...

[Yellow4g63]

Weld a aluminum pipe to it and never worry about it again.

[Coolwhip]

Or two part epoxy

[ANVIL]

Just finished up JB welding it back on after cleaning it up real good. Just gotta wait for it to dry and cure and I should be back on the road tomorrow night. I even took a mirror and actually confirmed a dried coolant trail from the underside of the inlet to the top of the waterpump area so this was definitely the leak.

Im just hoping fixing this fixes my orginal problem with coolant temps....

[ANVIL]

After fixing it I have to say I think my coolant temps are tje best ive seen. I drove it around city driving with a lot of stopping for like an hour and a half and saw the highest temp of 99C or 210F. Seems higher than most but isnt that pretty standard for peak temps on most engines? My motor now cools down much quicker than before dropping from high 90c's to high 70c's just idling after driving. When idling while I was bleeding and after I drove around to test again it would stay at 70-72c idling for 30 or so min.

Should I still be worried about coolant temps?

[Yellow4g63]

seems kinda low, maybe the Tstat is stuck open? or it's really cold out where you live.

[ANVIL]

It's pretty cold I live in Alaska. Its been high 30s to high 50F the past few weeks.

You think 99C / 210F is low?

[Darius]

99C is too high. The temps should range between 92-94C with a 300zx thermostat. Also, it sounds like the there is something wrong with the thermostat sticking open if the operating temps are anything below 92 after warming up.

[ANVIL]

Hmmm idk but has nismo tstat brand new when I installed and has probably less than 5 or 6k miles.

Ugh getting so tired of chasing this temp problem.

[Yellow4g63]

The nismo is a lower temp then. I thought u had stock 300zx. My 300zx (Autozone part not OEM) with the clutch fan idles at 89c-90c. When I drive it goes down to 85c.

[ANVIL]

I need to get more seat time to be sure but it peaked at 99C before going back down in city driving. Highway stays cooler

[Darius]

You may need to improve the seal between your fans and radiator. I'm not sure on your setup, but temps will rise if the cooling system is not 100%. You can help take load off of the cooling system by installing an oil cooler too. I have seen that help immensely.

[xracerx972]

Ive read normal temp is 70c, tstat opens at 76c and too hot is 86c.

Ive got an external oil cooler and twin elec fans, I rarely ever see 80c.. most of the time it hovers around 70c

[Nesquick]

I have a Nismo t-stat, Trust oil cooler, Koyo rad, and a bottle of water wetter.

On 35*c (95*F) days, I reach 90-93*C (195-200*F) on my defi gauge.

Never thought of if this was good or bad, seems alright to me (I think)