Dano417

jan.w

Almost identical issue on my 2003 Infiniti FX35, also has the VQ35DE, I was actually going to make a post but you seem to have somewhat similar symptoms. Here's my story:

Just replaced the head gasket (2 weeks ago), problem went away for 500km and came back today. For me, gentle driving seems to keep the issue at bay, but if I give it any more than 30-40% throttle, the following will happen:

• Lose cabin heat (starts blowing cold).
• Coolant level slowly start to rise in overflow.
• Lower rad hose cools down.
• Bypass hose on the front of the engine slowly cools down.
• Engine temp slowly rises until coolant boils over and sputters out of overflow tank.
• I *THINK* I smell exhaust gasses in overflow tank.

The fact that this issue went away completely for 500KM (regardless of how hard I pushed the car, and don't worry - I pushed it hard), leads me to believe that the components related to the cooling system are functional. Thermostat is opening when it's supposed to, fans are kicking in properly, water pump is functioning as it should, and the system is airtight under testing pressures (system tested overnight at 15psi, no leaks).

When I replaced the head gasket, I didn't get the heads machined, so my current theory is that the heads were originally warped, causing the gasket to be placed under high stress in a specific location, which led to the subsequent failure after only a few hundred KMs with the new gasket. As was the problem originally, I think this is a microscopic, or semi-failed gasket which only leaks exhaust gasses into the coolant under high loads (higher cylinder pressures). When the exhaust gases enter the coolant system, I assume they travel into the water pump which causes the pump to stall (or "slip" in the gases) and cease proper operation. This then leads to the loss of coolant flow and subsequent loss of cabin heat, cooling of lower rad hose, cooling of bypass hose on the front of the motor, and overheat.

My plan as of now is to pull the heads, get them machined this time, install a new head gasket, and pray that this adventure is over.

Did you get your heads machined when you did the head gasket?
Does anyone else have any other ideas? I'm getting pretty close to buying a crashed up FX at an auction and swapping in another motor.

phreaktor

iTrader: (22)

Something like this?


If your heat is blowing cold, It's likely got air in the system because the coolant isn't passing through the heater core. . As much as you think you got it all out, I bet you didn't. Are you bleeding it with a Lisle funnel or just lifting the front and cracking the bleeder?

phreaktor

iTrader: (22)

Fast forward to 19:50. This solved my symptoms and they never came back. i think the air got in the system when i installed my Throttle body spacer or plenum spacer.