Hey y'all,
I know these questions have been asked in countless threads, but I've been searching/reading old threads on the topic for days and just want to make sure I'm not missing anything.
Working on a 99' 100 series with 250k+ miles and pretty questionable maintenance history judging by the condition of most of the systems. Owner gave me a call, engine was "smoking", I anticipated a cooling system failure. I drive an '07 GX and haven't had to troubleshoot cooling issues before, so I figured I'd take a look since it seemed like a good opportunity to get familiar with the 2UZ. Not sure if the Heater T's were every serviced, and to no one's surprise, the hot-side T popped and made a mess. Engine was killed <60 seconds after this happening.
First, I replaced both T's and all 6 hoses with OEM parts. I don't believe coolant loss was excessive since the engine was killed nearly instantly, but after looking at the state of the coolant (appears to be a generic green coolant) etc., theres multiple things of concern that I've noted and wanted to get second opinions on. First off, the coolant reservoir was full to the brim when I got to the vehicle, I'm assuming because it filled up while the system was under pressure but did not have the chance to drain back into the system as it normally would because the system abruptly lost pressure before cooling off as a result of the T failure. I checked the radiator and did not see any coolant, so I topped that off with distilled water until full and then ran the engine with the cap off to try and get it up to temp and circulating. First couple times idling the engine for <3 minutes, observed a small but noticeable amount of what smelled and looked like smoke (no sweet coolant smell, white in color) that seemed to be coming somewhere close to the firewall underneath the engine (maybe heater core?). Temps were within acceptable range however, so i'm assuming/hoping this was actually just leftover coolant from the original spill burning off. After more research I decided to do a proper coolant top-off/burp incase the smoke was a result of the heater/core or other components overheating due to air in the system.
Before topping off / burping, I emptied out the coolant reservoir since it was filled to the brim, far past the full marker. I was greeted by a pretty hefty gel-block that had formed at the bottom of the reservoir, picture attached below. Hoping this is just the product of the coolant not being replaced in a timely manner, but the distinct brown portion of the gel that had formed at the bottom was concerning. From what I've read, this is either rust/corrosion of various parts of the system, or a sign of a bigger oil leak/head gasket issue. If anyone has any input on that let me know. After cleaning out the reservoir, I filled it back halfway between the low/full marks with prediluted prestone (best guess at what's in the system now), put a no spill-funnel on the radiator, and filled that to about 1/3 with prestone. Started the engine, and let it warm up on idle while watching coolant temp with a scanguage. Set the air to full heat and fan speed after a bit, temps were up to 185+, still wasn't getting any heat in the cabin, but after holding it briefly at ~2000rpm a couple of times heat started coming through and a decent amount of bubbles started coming up in the funnel on the radiator. I'd been occasionally squeezing the upper radiator hose, but it was still producing bubbles every time and getting increasingly too hot to touch. After letting it continue to idle, coolant in the radiator funnel was noticeably steaming or gassing off and temps were holding around 210, which still seemed high so I decided to cut the engine and let it cool for a bit. Upon reading a bit more, to my understanding the steaming of the coolant in the radiator/funnel is normal since the system was not under pressure.
After ~20 min, tried the process again, let it idle up to ~185, revved it from the throttle cable to ~2000rpm for 10-20 seconds at a time while monitoring it on the scanguage. This time temps stayed steady between 180-190. Let it idle for another 10 minutes, temps stayed put at around 185, heat was flowing full blast in the cabin, no air bubbles coming out in the funnel unless I squeezed the still-fairly hot radiator hose. Was still catching a minor burning/smoke smell the first time I attempted burping the system, but haven't seen or smelled anything in the last 20 min of running the engine so I'm hoping whatever was causing that has resolved itself.
Moving forward, I've reinstalled the radiator cap and let it sit for a few hours. Planning on doing a test drive and watching temps on the scanguage, and then doing a major coolant system flush ASAP. I have ~5 gallons of Toyota pink on hand from the dealership, couldn't find any original red.
I'm concerned that the Heater T failure could either been the result of a bigger issue in the coolant system/engine, or could have created new issues that I haven't identified yet even though the engine was theoretically killed before it had the chance to seriously overheat. I still haven't diagnosed what was causing the smoke-like smell/gas that I noticed the first couple time's attempting an idle, although its completely possible it was simply excess coolant burning off of the engine surfaces and I'm misidentifying the smell. The sludge in the reservoir, particularly the brown portion of it is concerning. Additionally, I've put a total of 1 gallon of distilled water and 1 gallon of prestone 50/50 in the system, so I want to double check that that isn't an unusual amount of coolant loss for a heater T failure (keep in mind I did dump out the 100% full coolant reservoir). I was considering thermostat failure when temps were high and I wasn't getting any heat on the first burp attempt, but on the second attempt I had no heat issues and a constant 185F idle so I think I might be good temporarily in that regard. Not seeing any coolant loss since replacing the T's. Rear heat button neither actives nor does the button light up when pressed, but I believe that was a preexisting issue and haven't considered it to be directly related. Oil looks good at a quick glance, no milky appearance.
TLDR, I'm still worried about a head gasket problem, although most of the issues that were pointing me towards that have ironed themselves out. Planning on doing an extensive coolant flush with tap-water out of a hose followed by 3-4 cycles of distilled water and then refilling with prediluted OEM pink. If a chemical flush is necessary given the sludge found in the reservoir, what would y'all recommend I purchase for that? I know this is amateur stuff and I apologize for word-dumping on well-documented issues, but if anyone takes the time to read through this short-essay and notices any red-flags or things I should be aware of please let me know.
Thank y'all
I know these questions have been asked in countless threads, but I've been searching/reading old threads on the topic for days and just want to make sure I'm not missing anything.
Working on a 99' 100 series with 250k+ miles and pretty questionable maintenance history judging by the condition of most of the systems. Owner gave me a call, engine was "smoking", I anticipated a cooling system failure. I drive an '07 GX and haven't had to troubleshoot cooling issues before, so I figured I'd take a look since it seemed like a good opportunity to get familiar with the 2UZ. Not sure if the Heater T's were every serviced, and to no one's surprise, the hot-side T popped and made a mess. Engine was killed <60 seconds after this happening.
First, I replaced both T's and all 6 hoses with OEM parts. I don't believe coolant loss was excessive since the engine was killed nearly instantly, but after looking at the state of the coolant (appears to be a generic green coolant) etc., theres multiple things of concern that I've noted and wanted to get second opinions on. First off, the coolant reservoir was full to the brim when I got to the vehicle, I'm assuming because it filled up while the system was under pressure but did not have the chance to drain back into the system as it normally would because the system abruptly lost pressure before cooling off as a result of the T failure. I checked the radiator and did not see any coolant, so I topped that off with distilled water until full and then ran the engine with the cap off to try and get it up to temp and circulating. First couple times idling the engine for <3 minutes, observed a small but noticeable amount of what smelled and looked like smoke (no sweet coolant smell, white in color) that seemed to be coming somewhere close to the firewall underneath the engine (maybe heater core?). Temps were within acceptable range however, so i'm assuming/hoping this was actually just leftover coolant from the original spill burning off. After more research I decided to do a proper coolant top-off/burp incase the smoke was a result of the heater/core or other components overheating due to air in the system.
Before topping off / burping, I emptied out the coolant reservoir since it was filled to the brim, far past the full marker. I was greeted by a pretty hefty gel-block that had formed at the bottom of the reservoir, picture attached below. Hoping this is just the product of the coolant not being replaced in a timely manner, but the distinct brown portion of the gel that had formed at the bottom was concerning. From what I've read, this is either rust/corrosion of various parts of the system, or a sign of a bigger oil leak/head gasket issue. If anyone has any input on that let me know. After cleaning out the reservoir, I filled it back halfway between the low/full marks with prediluted prestone (best guess at what's in the system now), put a no spill-funnel on the radiator, and filled that to about 1/3 with prestone. Started the engine, and let it warm up on idle while watching coolant temp with a scanguage. Set the air to full heat and fan speed after a bit, temps were up to 185+, still wasn't getting any heat in the cabin, but after holding it briefly at ~2000rpm a couple of times heat started coming through and a decent amount of bubbles started coming up in the funnel on the radiator. I'd been occasionally squeezing the upper radiator hose, but it was still producing bubbles every time and getting increasingly too hot to touch. After letting it continue to idle, coolant in the radiator funnel was noticeably steaming or gassing off and temps were holding around 210, which still seemed high so I decided to cut the engine and let it cool for a bit. Upon reading a bit more, to my understanding the steaming of the coolant in the radiator/funnel is normal since the system was not under pressure.
After ~20 min, tried the process again, let it idle up to ~185, revved it from the throttle cable to ~2000rpm for 10-20 seconds at a time while monitoring it on the scanguage. This time temps stayed steady between 180-190. Let it idle for another 10 minutes, temps stayed put at around 185, heat was flowing full blast in the cabin, no air bubbles coming out in the funnel unless I squeezed the still-fairly hot radiator hose. Was still catching a minor burning/smoke smell the first time I attempted burping the system, but haven't seen or smelled anything in the last 20 min of running the engine so I'm hoping whatever was causing that has resolved itself.
Moving forward, I've reinstalled the radiator cap and let it sit for a few hours. Planning on doing a test drive and watching temps on the scanguage, and then doing a major coolant system flush ASAP. I have ~5 gallons of Toyota pink on hand from the dealership, couldn't find any original red.
I'm concerned that the Heater T failure could either been the result of a bigger issue in the coolant system/engine, or could have created new issues that I haven't identified yet even though the engine was theoretically killed before it had the chance to seriously overheat. I still haven't diagnosed what was causing the smoke-like smell/gas that I noticed the first couple time's attempting an idle, although its completely possible it was simply excess coolant burning off of the engine surfaces and I'm misidentifying the smell. The sludge in the reservoir, particularly the brown portion of it is concerning. Additionally, I've put a total of 1 gallon of distilled water and 1 gallon of prestone 50/50 in the system, so I want to double check that that isn't an unusual amount of coolant loss for a heater T failure (keep in mind I did dump out the 100% full coolant reservoir). I was considering thermostat failure when temps were high and I wasn't getting any heat on the first burp attempt, but on the second attempt I had no heat issues and a constant 185F idle so I think I might be good temporarily in that regard. Not seeing any coolant loss since replacing the T's. Rear heat button neither actives nor does the button light up when pressed, but I believe that was a preexisting issue and haven't considered it to be directly related. Oil looks good at a quick glance, no milky appearance.
TLDR, I'm still worried about a head gasket problem, although most of the issues that were pointing me towards that have ironed themselves out. Planning on doing an extensive coolant flush with tap-water out of a hose followed by 3-4 cycles of distilled water and then refilling with prediluted OEM pink. If a chemical flush is necessary given the sludge found in the reservoir, what would y'all recommend I purchase for that? I know this is amateur stuff and I apologize for word-dumping on well-documented issues, but if anyone takes the time to read through this short-essay and notices any red-flags or things I should be aware of please let me know.
Thank y'all
