perrobravo
SILVER Star
Looking for help solving a new problem with my 1HDT. After replacing the head gasket for unrelated reasons, the truck consistently pushes coolant into the overflow when driven under load. I've read every burping thread, searched extensively for ideas, have tried a dozen things, and have run out of ideas. Any help would be appreciated!
Observations:
Truck starts immediately, runs great, and pulls very well through the rev range
No unexpected smoke from the exhaust (just a puff of black on startup)
Engine temps (measured by factory gauge) normal, never budge once up to temp
EGTs in check, never exceed 1200F (most of the time far lower), reasonable AFR through rev range
No visible water or oil leaks
~320k on the odometer
New GTurbo green wheel (boost set to max ~23)
Injectors and injection pump rebuilt (timing set to factory spec)
PDI front mount intercooler
Torfab airbox and aneroid pin
EGTs in check, has never exceeded 1200F, reasonable AFR through rev range
Problem:
Under load (i.e. uphill, high speed, pushing a bit harder than just driving to the local dealer to buy more coolant), coolant is pushed into overflow and doesn't get drawn back into the radiator when the engine cools. A couple times, the overflow overflowed and dumped coolant onto the ground. Most often it simply fills the overflow, but I haven't been pushing it to avoid making the problem worse.
Tests completed:
Checked for bubbling of coolant in radiator...none other than usual flow of water once thermostat opens
Oil and coolant appear clean visually (no milkiness or other bad signs)
Oil tested by Blackstone (no indication of coolant making its way into the oil...I specifically asked them to look)
No sign of compression gases in coolant (using 2 different test kits in both overflow and radiator)
Cooling system holds pressure (tested to 16psi)
Compression at sea level (on cold engine) 510-525psi (maybe a bit high, but could be my cheap gauge isn't as accurate as it should be)
Work done recently:
Head resurfaced, tested for cracks (none)
Valves cleaned up, new OEM stem seals, lash set to factory spec
New OEM head gasket (the right one based on the number of tabs on original)
New OEM head bolts torqued per FSM instructions
New OEM radiator and radiator cap (0.9bar)
Coolant drained and flushed (including block and heater core...which seemed very clean)
Rear heater deleted
New 50/50 mix of Toyota red coolant
New OEM thermostat (installed with the jiggle thing at the top per the FSM)
Used Venturi compressed air/vacuum coolant fill tool with front end on ramps, truck on an inclined driveway, heater on
I'm hoping this is simply an air pocket somewhere in the engine, but I've tried multiple times to burp the system and haven't read too many stories of people struggling with this on this engine. I don't want it to be something I screwed up when replacing the head gasket, but also don't know what else to test to confirm/deny this. I wouldn't love doing the head gasket work again, but would IF I was confident doing so would fix the problem.
Anyone have ideas? I know there are quite a few folks here deep into 1HDT engines, so maybe some specific tips or something I'm missing? @Onur @SNLC @torfab @Loober ?
And a picture, just because
Observations:
Truck starts immediately, runs great, and pulls very well through the rev range
No unexpected smoke from the exhaust (just a puff of black on startup)
Engine temps (measured by factory gauge) normal, never budge once up to temp
EGTs in check, never exceed 1200F (most of the time far lower), reasonable AFR through rev range
No visible water or oil leaks
~320k on the odometer
New GTurbo green wheel (boost set to max ~23)
Injectors and injection pump rebuilt (timing set to factory spec)
PDI front mount intercooler
Torfab airbox and aneroid pin
EGTs in check, has never exceeded 1200F, reasonable AFR through rev range
Problem:
Under load (i.e. uphill, high speed, pushing a bit harder than just driving to the local dealer to buy more coolant), coolant is pushed into overflow and doesn't get drawn back into the radiator when the engine cools. A couple times, the overflow overflowed and dumped coolant onto the ground. Most often it simply fills the overflow, but I haven't been pushing it to avoid making the problem worse.
Tests completed:
Checked for bubbling of coolant in radiator...none other than usual flow of water once thermostat opens
Oil and coolant appear clean visually (no milkiness or other bad signs)
Oil tested by Blackstone (no indication of coolant making its way into the oil...I specifically asked them to look)
No sign of compression gases in coolant (using 2 different test kits in both overflow and radiator)
Cooling system holds pressure (tested to 16psi)
Compression at sea level (on cold engine) 510-525psi (maybe a bit high, but could be my cheap gauge isn't as accurate as it should be)
Work done recently:
Head resurfaced, tested for cracks (none)
Valves cleaned up, new OEM stem seals, lash set to factory spec
New OEM head gasket (the right one based on the number of tabs on original)
New OEM head bolts torqued per FSM instructions
New OEM radiator and radiator cap (0.9bar)
Coolant drained and flushed (including block and heater core...which seemed very clean)
Rear heater deleted
New 50/50 mix of Toyota red coolant
New OEM thermostat (installed with the jiggle thing at the top per the FSM)
Used Venturi compressed air/vacuum coolant fill tool with front end on ramps, truck on an inclined driveway, heater on
I'm hoping this is simply an air pocket somewhere in the engine, but I've tried multiple times to burp the system and haven't read too many stories of people struggling with this on this engine. I don't want it to be something I screwed up when replacing the head gasket, but also don't know what else to test to confirm/deny this. I wouldn't love doing the head gasket work again, but would IF I was confident doing so would fix the problem.
Anyone have ideas? I know there are quite a few folks here deep into 1HDT engines, so maybe some specific tips or something I'm missing? @Onur @SNLC @torfab @Loober ?
And a picture, just because