So I have a 7MGTE that i just rebuilt less than 5k miles ago and im having some cooling system problems. I figured i would post here about it to get some ideas on diagnosing it. I will put down all the symptoms i have found etc and what tests ive done so far/what i plan to do.
Basically the engine is as follows:
7MGTE block/head
89+ block and no cracks between water jacket and headbolt holes
Probe .040" pistons
Cometic .065" MLS head gasket
New valve seals lapped valves reshimmed etc
All new gaskets/seals
Head and block both machined to BELOW 30RA
All new hoses
Intake/stock turbo elbo/3"dp/2.5"exhaust/stock intercooler/piping/stock rebuilt turbo/stock boost(7psi)
ARP head studs with ARP lube
Studs torqued in stages (30ft lbs, back all off, 50 ft lbs, back all off etc until 80 ft lbs)
Studs retorqued after 4 heat cycles (83ft lbs)
Basically i drove the car with no issues for over 1-2k miles, and then slowly started hearing a trickle behind the dash in the cold mornings. Soon, I started hearing the trickle on startup even when it wasnt cold. When i would squeeze the upper radiator hose i could hear/feel some air in it. I purged all the air, but the noise would continue to come back
The car does not overheat at all, temps are always normal. There are no external leaks of any kind, my heater works fine and does not smell funny, no signs of leakage, no fogging windshield etc.
I took the car out one night and did some hard runs with it up to about 80 a couple times on the highway and after i got off the freeway and waited at the light, i heard the waterfall when i took off from the stop. It was louder than i had ever heard it before. I put it in the garage and decided to retorque the head again, this time i took it up to 90ft lbs. I drove the car about a week and the waterfall had gone away, wasnt getting any air in the system anymore.
Then it was hot one day(a day or two later) so i decided to use my AC, I had it on full blast around town, no signs of anything bad. Took the car on the highway for about 10 mins, then coasted to a stop after i exited and sat there idling with ac on high for aboiut 2-3 minutes. After i took off from the stoplight i heard a trickleing noise again, and after letting it sit overnight there was airr in the upper hose again.
After driving it around normally a few days the air has purged out once again and hasnt returned yet. I drove the car hard, and theres no signs of air in the system, but i have yet to try turning the ac on full blast again sitting idle on a hot day. Coolant temps never rose above 200 deg. BTW.
Really would love to get some ideas on this. Everything was machined to specs, rear timing plate on the block and all. Even removed a rivet that looked like it might interfere on the HG.
The car never has lost any coolant, never saw any smoke out the tailpipe, never smelled sweet exhaust, i checked all the plugs and pistons, all pistons had carbon on top and all plugs looked to be perfect in color (tan). I thought at first coolant was boiling in the turbo after shutdown, so i had bypassed the turbo coolant lines prior to the retorque to eliminate the possibility.
My next steps are block test and cooling system pressure test. I just posted this to get some ideas on what to check, maybe things i overlooked. I know its long but i wanted to give all the detail i could. Thanks for any tips.
Basically the engine is as follows:
7MGTE block/head
89+ block and no cracks between water jacket and headbolt holes
Probe .040" pistons
Cometic .065" MLS head gasket
New valve seals lapped valves reshimmed etc
All new gaskets/seals
Head and block both machined to BELOW 30RA
All new hoses
Intake/stock turbo elbo/3"dp/2.5"exhaust/stock intercooler/piping/stock rebuilt turbo/stock boost(7psi)
ARP head studs with ARP lube
Studs torqued in stages (30ft lbs, back all off, 50 ft lbs, back all off etc until 80 ft lbs)
Studs retorqued after 4 heat cycles (83ft lbs)
Basically i drove the car with no issues for over 1-2k miles, and then slowly started hearing a trickle behind the dash in the cold mornings. Soon, I started hearing the trickle on startup even when it wasnt cold. When i would squeeze the upper radiator hose i could hear/feel some air in it. I purged all the air, but the noise would continue to come back
The car does not overheat at all, temps are always normal. There are no external leaks of any kind, my heater works fine and does not smell funny, no signs of leakage, no fogging windshield etc.
I took the car out one night and did some hard runs with it up to about 80 a couple times on the highway and after i got off the freeway and waited at the light, i heard the waterfall when i took off from the stop. It was louder than i had ever heard it before. I put it in the garage and decided to retorque the head again, this time i took it up to 90ft lbs. I drove the car about a week and the waterfall had gone away, wasnt getting any air in the system anymore.
Then it was hot one day(a day or two later) so i decided to use my AC, I had it on full blast around town, no signs of anything bad. Took the car on the highway for about 10 mins, then coasted to a stop after i exited and sat there idling with ac on high for aboiut 2-3 minutes. After i took off from the stoplight i heard a trickleing noise again, and after letting it sit overnight there was airr in the upper hose again.
After driving it around normally a few days the air has purged out once again and hasnt returned yet. I drove the car hard, and theres no signs of air in the system, but i have yet to try turning the ac on full blast again sitting idle on a hot day. Coolant temps never rose above 200 deg. BTW.
Really would love to get some ideas on this. Everything was machined to specs, rear timing plate on the block and all. Even removed a rivet that looked like it might interfere on the HG.
The car never has lost any coolant, never saw any smoke out the tailpipe, never smelled sweet exhaust, i checked all the plugs and pistons, all pistons had carbon on top and all plugs looked to be perfect in color (tan). I thought at first coolant was boiling in the turbo after shutdown, so i had bypassed the turbo coolant lines prior to the retorque to eliminate the possibility.
My next steps are block test and cooling system pressure test. I just posted this to get some ideas on what to check, maybe things i overlooked. I know its long but i wanted to give all the detail i could. Thanks for any tips.
