I've got a bit of a head scratcher.

About a year ago I blew my head gasket at 134k miles on the engine. I'm the second owner and don't believe it had been replaced before I bought it. I bought and installed the Atlantic British kit (STC4082BKA). Heads were in good shape and block was good. Replaced the thermostat with AB's Warm Weather Climate version (PEL500110). Replaced the water pump, all coolant hoses and radiator.

A few months later I noticed I was getting misfires on Cyl 1 and 8. Replaced plugs and wires with AB's Champion service kit (NLP100320SKA). Still got an occasional misfire but started noticing a coolant leak. After pressure testing coolant system I ended up replacing the throttle body heater plate (leaking) and the expansion tank hose (also cracked and leaking). My coolant loss continued. I then replaced the expansion tank and cap both from AB. Pressure tested and it was good. After taking a few test drives of a couple miles I was still losing coolant but no obvious leaks or misfires. I'd lose half the expansion tank wait until cooled down and refill most of the way only to check it again a few hours later and it was overfilled. I pressure tested the system one last time and am now burning coolant - lot's of white sweet smelling smoke on startup which clears out after it warms up. I'm not overheating and temps are running at 186-194 at idle maxing out at 200 on a drive but then back down to 194. I'm not getting any misfires or other codes now. Oil looks good - it's not milky.

So after all the above I'm at a loss as to what the issue is. Did the head gaskets blow again? Seems unlikely after less than 5k miles. Is there any other explanation for the coolant burn on startup??

Any help would be most appreciated.

 

You said you pressure tested system one last time ? What were the results ?
Either you messed up the gasket install or block is cracked
head gasket leak I think would steam clean the piston it’s leaking into

 

The system held at 16psi after I installed the new expansion tank and for the final test.
I'll be doing a compression test on all cylinders this week.
The HG install was done by a shop with a good rep so I'd hope thy didn't mess that up.

 

Maybe it only leaks while it’s hot

 

I had almost the same issue as you and it got worse over time. To the point where I was eating 1 cup of coolant and the expansion tank would hold pressure for days. I replaced the head gaskets and while doing so, I could not see any obvious sign of a blown gasket or slipped liner. However, cylinders 1,3,4 looked way too clean. Since doing the head gaskets and driving about 200 miles, I have not seen any loss of coolant and expansion tank does not have any pressure the following day.

What could it be...maybe one or two of the head bolts didn't torque correctly and is allowing the coolant to get into the cylinders.

 

redwhitekat - exhaust runs clear once it's hot which seems to suggest that once it's up to temp that the leak gets sealed

Friday Night Disco - I was wondering the same thing about the head bolts.

 

Before you go for another head gasket and nothing else works...hit the head bolts with a 1/2 breaker bar again.

 

Do you have a borescope? Can you borrow one?

Take the plugs out, let it sit, put a scope in each chamber to see if there is any coolant present.

 

I have a friend coming out on thrursday to help with the compression test - I'll see if I can get one - that's a good idea too

 

After checking the compression and inspecting each cylinder with a scope it appears I've got a blown head gasket. All the head bolts were pretty tight.
Compression was a little odd but seems to be in specs.
Right
cyl 1 185 (wet cylinder and clean plug)
cyl 3 155
cyl 5 162
cyl 7 142
Left
cyl 2 153
cyl 4 158
cyl 6 160
cyl 8 176