Oil Film when doing coolant flush

rfj62

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I was doing a coolant flush on my '90 3FE. I used a chemical cleaner and let it soak and then drive it to thoroughly get into all aspects of the cooling system, over a week. When I started I wasn’t getting a lot of heat out of the heaters, front or rear heater, but now they are super hot. I couldn't believe the junk that came out. I thought I was good, but now I’m not so sure. I put in clean water but I always get a little bit of oil (I believe) out into the bucket. I water flushed it for a few hours but it is not oil free. I flushed it with out the running the rear heater, then the front heater but always the same result. I recently changed a lot of gaskets on the engine, side cover, oil pan, oil cooler, basically any gaskets that include oil in the engine and all the coolant hoses where changed, except the ones going into the firewall. When I drained the oil I didn't notice any water in the oil. Do the heater systems use oil? Oil cooler bad? Any thought?

TIA
Jeff
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OSS

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A little oil getting into the cooling system isn’t harmful at all. The opposite isn’t true.
Keep an eye on the motor oil and coolant level. If there’s no water contamination in the oil and you’re not losing coolant as you drive - you’re fine.
 

rfj62

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A little oil getting into the cooling system isn’t harmful at all. The opposite isn’t true.
Keep an eye on the motor oil and coolant level. If there’s no water contamination in the oil and you’re not losing coolant as you drive - you’re fine.
Thanks for the info. That is a huge relief! I'll keep an eye on the oil. Time to add the Toyota red and move on.
 

micruz60

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Agreed with OSS, doing all the hoses and gaskets would eliminate most sources of oil contamination; as a favor to the forum, what was the chemical cleaner you used?
Thanks
 

rfj62

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Agreed with OSS, doing all the hoses and gaskets would eliminate most sources of oil contamination; as a favor to the forum, what was the chemical cleaner you used?
Thanks
I ended up using 2 different ones. I used ThermoCure by EvapoRust, THERMOCURE™ - Cooling System Rust Remover & Flush | EVAPO-RUST® - https://www.evapo-rust.com/thermocure/. I thought I was being smart by not putting in the new thermostat until I did the coolant flush, but I was wrong. I didn't consider that the heater cores wouldn't open up completely until the truck got up to the right temp, which it never did with the thermostat remove. After I figured that out, I ended up using Preston coolant flush Prestone® Total Cooling System Cleaner - Prestone® Total Protection - https://prestone.com/product/prestone-total-cooling-system-cleaner/. Both seemed to really clean the system out, a lot of black junk and rusty water after using them. Can't say if one was better than the other one.
 

micruz60

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I've got to do a flush, hopeful that will clear my front heater core. . .
 

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