What sort of coolant should I use?

[mvrk]

Hello all,

The previous owners of my SW20 deleted the engine half of the heater system, and when I took it to a workshop, I was consulted to use water as coolant. Is this the right procedure? The engine just sips through the water I put into it and I'd hate to keep checking the water level under the coolant cap every other day...

Extra bit of details, there is no thermostat, water is just flowing through the system thermostat free.

-Maverick

[Benckj]

Regardless of what components were deleted and for what reason you should run antifreeze with corrosion protection in system. Antifreeze not only lowers the freezing point of water but also raises the boiling point. It contains ant-corrosion additives to keep the PH of fluid below acidic level. This is also critical in the MR2 as if not maintained will lead to internal corrosion which will cause serious issues within the system.

[GDII]

Jim is right. You need to run antifreeze.

Water is the best at heat transfer, even Castrol themselves state this but you need to run antifreeze for the reason Jim mentions. Raises boiling point, lowers freezing and is anti corrosion for protection of your engine and cooling system.

You need to find why it is using water and why the thermostat has been removed.
The heater pipes will most likely have a leak in the brass pipe running from the engine bay to the front. This will be why they have removed it. This is very common on the SW20 and it's a little tricky to fix due to having to take the fuel tank out. Not impossible but not ideal.

[mvrk]

Regardless of what components were deleted and for what reason you should run antifreeze with corrosion protection in system. Antifreeze not only lowers the freezing point of water but also raises the boiling point. It contains ant-corrosion additives to keep the PH of fluid below acidic level. This is also critical in the MR2 as if not maintained will lead to internal corrosion which will cause serious issues within the system.

Jim is right. You need to run antifreeze.

Water is the best at heat transfer, even Castrol themselves state this but you need to run antifreeze for the reason Jim mentions. Raises boiling point, lowers freezing and is anti corrosion for protection of your engine and cooling system.

You need to find why it is using water and why the thermostat has been removed.
The heater pipes will most likely have a leak in the brass pipe running from the engine bay to the front. This will be why they have removed it. This is very common on the SW20 and it's a little tricky to fix due to having to take the fuel tank out. Not impossible but not ideal.

Right, that's what I initially thought. It seemed wrong to use straight up water. What coolant should I eventually pour into the system? I'm getting a few conflicting answers on what coolant Sw20s should use.

I probably can't get a reason as to why the deleted components were deleted and why water was used as coolant. This Sw20 has several previous owners under it's belt and trying to hunt down who removed the components would be like finding a needle in a haystack. Not having a heater isn't a big deal since I have a ton of sweaters Though, if someone nearby is wreaking their Sw20 3SGE, I'll consider doing the heater system.

[GDII]

I guess the best thing to do is to determine the source of the leak/usage of coolant.

Putting in a thermostat would be a good idea. Get one from Toyota as the other aftermarket brands fail too quickly.

What parts of the heater system have been removed?
If you can get a photo of the front of the car like this

Showing this part


And the engine bay around this area circled in red


We can then determine what's missing.

[Benckj]

What coolant should I eventually pour into the system? I'm getting a few conflicting answers on what coolant Sw20s should use.

Toyota used a 'Red' Long life coolant which many owners swear by. I tend to use the 'Green' type long life coolant as its more readily available, less expensive and consistant with my others cars. Never had an issue with it but I do maintain this fluid more than most owners.

The important part is not to mix the two different types. Whatever you decide on, stick with it.

[mvrk]

I guess the best thing to do is to determine the source of the leak/usage of coolant.

Putting in a thermostat would be a good idea. Get one from Toyota as the other aftermarket brands fail too quickly.

What parts of the heater system have been removed?
If you can get a photo of the front of the car like this

Showing this part


And the engine bay around this area circled in red


We can then determine what's missing.

It seems like nothing has been removed from the front:

But on the engine side, it seems like a whole lot was taken out:

[GDII]

]You are just missing the hoses from the water neck or tree to the heater pipes. Your pipes are still there. The top one is probably leaking when connected so they removed the hoses. There must be a loop or block off on the engine connection.

SW20 MR2 heater pipes.JPG (226.03 KiB) Viewed 1367 times

You are looking for hoses with the PNC of 87245A and 87246B. 87208C is probably still there. I don't think Toyota sell these but it gives you a reference on what to ask for on a used car.

[mvrk]

]You are just missing the hoses from the water neck or tree to the heater pipes. Your pipes are still there. The top one is probably leaking when connected so they removed the hoses. There must be a loop or block off on the engine connection.

SW20 MR2 heater pipes.JPG

You are looking for hoses with the PNC of 87245A and 87246B. 87208C is probably still there. I don't think Toyota sell these but it gives you a reference on what to ask for on a used car.

Yeah, I did see that diagram online, I just didn't entire understand where the hoses connect to. Do you know roughly where the engine connection is? I'll have a look next time I'm underneath the car.

[GDII]

The on the far left goes too the heater


The other one is on top of the gearbox near the starter motor.
See if you can shove the camera in the engine bay around this area and snap some shots. I might be able to sight what's been done and circle it for you.

[GDII]

Interesting. This part is still available here it appears. Top hose to the heater core.
http://www.butlerautomart.co.nz/our-ran ... H2834.aspx

[mvrk]

Interesting. This part is still available here it appears. Top hose to the heater core.
http://www.butlerautomart.co.nz/our-ran ... H2834.aspx

Thank you. I'll keep my eyes out for the time being. I ended up putting the green coolant into the system, and I don't know if I should be worried or not; is this the normally operating temp?

[mvrk]

Interesting. This part is still available here it appears. Top hose to the heater core.
http://www.butlerautomart.co.nz/our-ran ... H2834.aspx

Thank you. I'll keep my eyes out for the time being. I ended up putting the green coolant into the system, and I don't know if I should be worried or not; is this the normally operating temp?20210223_175006.jpg

Update: Nevermind. My system is just adjusting to the new coolant, it's back to levels it was before when I used water

[GlanzaAtHeart]

Interesting. This part is still available here it appears. Top hose to the heater core.
http://www.butlerautomart.co.nz/our-ran ... H2834.aspx

Thank you. I'll keep my eyes out for the time being. I ended up putting the green coolant into the system, and I don't know if I should be worried or not; is this the normally operating temp?20210223_175006.jpg

Yeah that's normal operating temp, good work

[GDII]

Interesting. This part is still available here it appears. Top hose to the heater core.
http://www.butlerautomart.co.nz/our-ran ... H2834.aspx

Thank you. I'll keep my eyes out for the time being. I ended up putting the green coolant into the system, and I don't know if I should be worried or not; is this the normally operating temp?20210223_175006.jpg

Yeah that's normal operating temp, good work

What is shown in the photo is a bit low but he now says it back up to the middle.

You are bleeding it as per the service manual? Just checking as I'm not sure what you know about the MR2 and bleeding the coolant system is very specific on these cars.