Question about coolant noise in front of cam cover

[nbskyline]

Newer engine from Z-Tune that I finally got in this year. It has some rust through the coolant system from sitting so long but looks alright now, few flakes here and there. Compression tested twice, 150 across the board!! Oil temps seem to run about 100 and coolant temp is perfect. Only real concern is the damn coolant bubbling noise at the front cam cover ( pipe coming from turbo's ) Any suggestions?? Have bleed the system several times.

Thanks

[DarkCaporaL]

I'm guessing you hear boiling when you shut if off?

If it's not a failed HG making the coolant overheat (you would have pressure in the rad and coolant would be flowing out like a fountain, and either oil in coolant and/or milky oil), then the system is likely not pressurized correctly or not staying pressurized = air in the system.

First step would be to bleed the system, make sure you use the bleeding screw on top of the plenum next to the FPR as well as this is the highest point. Start the car with the rad cap off (while car is cool), let the car heat up until the thermostat opens and the coolant starts flowing. Thermostat should open at 73.6C, if it doesn't it's prob faulty. Once it's flowing, give it a bit of gas in quick jolts and if there is air in the system you will see bubbles coming out of the radiator. Continue until no air comes out, and ensure to fill up the coolant reservoir.

If you are sure the car is bled correctly and there is no air in the system, then that means the system is leaking and letting air in. The easiest and most common part is the rad cap. If it's old it might not be able to hold the pressure required to keep the system pressurized and prevent the coolant temps from rising after shut off. OEM one is 0.9 bar. If its not the rad cap then there is another leak elsewhere. Check under the car for any signs of coolant leaks.

Note that it's normal for the coolant temp to rise a bit after shut off since the water pump is not flowing the coolant anymore, you could try and let the car idle a couple minutes before shutting off and see if it helps, but more than likely you have a leak/air somewhere.

[nbskyline]

Thanks for the reply, i am going to get a new rad cap and try rebleeding to system. The noise starts about 20 seconds after i shut down. Compression results should rule out HG? oil looks good, coolant looks good except for a few rust flakes here and there, no white smoke.

Thanks

[DarkCaporaL]

Yeah doesn't sound like your HG is toast, it's pretty obvious when it is.

Yeah if it starts about 20 seconds after it's because the temp is slowly rising (if you have an aftermarket water temp gauge you will see this easily). It's normal for the temps to rise a bit, but if it gets to boiling point it's usually because it's losing pressure.

Let us know your results!

[nbskyline]

okay, here is a dumb question. I can not locate the same rad cap. Only 16 PSI. Does anyone know what it is compatible with or even a part #. Trying to find anyone to help at Canadian Tire is useless.

Thanks

[DarkCaporaL]

Try calling a Nissan dealership if CrappyTire doesn't have it and see if you can get an OE 0.9 bar rad cap. It's generic anyways.

You could also try any autoparts store like Napa or something.

Should be around 10$.

[nbskyline]

update: new rad cap, i get a slight flowing coolant sound at the cam cover about 2 minutes after I shut it off? It only lasts for about 30 seconds.
My oil temp is still riding about 100-105 in the time to idle to temp, bleed coolant then go for a 15 minute drive about 80km an hour?? Coolant temp staying just below half, where it should. I haven't really driven the car more than 1/2 hour at a time until I can get this figuired out.
Once the thermostat open I get a few very small bubbles that go away once it starts flowing. I appreciate all your help so far, any more input would be great.

Thanks

[DarkCaporaL]

update: new rad cap, i get a slight flowing coolant sound at the cam cover about 2 minutes after I shut it off? It only lasts for about 30 seconds.

Flowing or boiling? The only thing that comes to mind is it might be the thermostat slowly closing and you can hear the effect it has on the flow?

My oil temp is still riding about 100-105 in the time to idle to temp

Those are a bit high but not necessarily abnormal. Oil temps will rise when the car is stationary, for me for example, they go to about 95 if I'm stuck in traffic, and since I have an oil cooler when I'm moving they go down to 80.

I don't know if you did, but considering you said that your coolant had rust flakes in it earlier, you might want to consider flushing the old coolant out and putting new one in.

[cortexx]

The noise is normal , the water in the turbos heats up causing coolant to flow through this pipe . It is an intended effect to help stop the oil in the turbos overheating and turning to carbon once circulation stops when you switch off the engine . The coolant is cirulating using a phenomena called thermal convection It's a good thing , mine does it too !

[DarkCaporaL]

The noise is normal , the water in the turbos heats up causing coolant to flow through this pipe . It is an intended effect to help stop the oil in the turbos overheating and turning to carbon once circulation stops when you switch off the engine . The coolant is cirulating using a phenomena called thermal convection It's a good thing , mine does it too !

Good explanation, I'll check mine next time I drive it, I've never noticed it.

[nbskyline]

Thanks guys It sounds like flowing, fast, i think. Like a gushing sound, as if it is being forced through. I will try another flush this weekend as well as i am still seeing rust coming tp the top.

[Bruizer]

That seems hot. What kind of gauge and where is the sensor? Upper lower rad hose?

Maybe I'm out to lunch but my defy gauge says 65-75 when driving normal to wot driving. Sensor is in upper rad hose. I had my coolant temp hit 100 1 day but my timing was out 20 degrees. Now it's fine

Anyway. I always hear bubbling sounds when turned off. That's at
Pockets moving around I think. Air separator fixes that usually no?

[MarusGTR]

The coolant is cirulating using a phenomena called thermal convection It's a good thing , mine does it too !

To be more precice, it's natural convection, since it's not induced mechanically. I've never noticed that sound in mine but that's probably because I always stay a little in idle to cool it down (cause I'm a hobo and don't care for the intricacies of a turbo timer).