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Coolant change

6K views 30 replies 10 participants last post by  Fillspyder 
#1 ·
Hey guys

Preparing for a coolant change and the BGB says to 'replace the gaskets at the same time' (page CO-2) without other specifics. The book is referencing the various drain plugs: One in the radiator, one in each of the coolant lines front to back, and the one in the engine block(?).

I found the part numbers for three of the drains. The radiator plug gasket (16492-21050). the 2 coolant line plug gaskets (90430-08008), but I can't find the part number, or even if there is a gasket, for the drain plug on the engine. One T dealer said there is no gasket on the engine drain plug. The other didn't know.

Does someone here know the part number for the gasket on the engine drain plug? Or the less likely scenario, that there actually isn't one?

And does anyone have a photo or two of the drain plug in the engine? So I can see where it is exactly and what it looks like. I assume you need to get under the car for the engine plug, and I've heard people say you need to be a contortionist t reach it...

Thanks All!
 
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#3 ·
Thanks Phat
So no need to remove the lower radiator plug or the engine plug? That certainly makes things easier.
I've seen alot of complaints of people not properly bleeding all the air out and having overheating isues. Any tricks? Or is it just patience...
Supposed to keep the car level for the replacement. Is there enough space to get at the 2 bolts and get a drain pan under without using 4 jack stands? I'm reading that out loud and shaking my head no, probably not...
 
#5 ·
There is, I believe, a YouTube video on the process. Pull the plugs in pipes running center of car, heater open and plug (more a spigot) in block open. Close drains, keep air lock tubes open - all as instructed. Refill - except procedure worked best for me by getting the liquid in car while level as instructed in the BGB. Then run it. As you run it, jack the back of the car up high. Add fluid intermittently. Burping done.
 
#6 ·
The radiator and heater core do not have a drain plug, but they do have a petcock, which you unscrew to empty them of coolant. Per the BGB, you then attach a length of clear tubing to each, and suspend them(tape them up), attached to the underside of the hood. This allows air to escape from the system as you are refilling. All of this is detailed in the BGB Instructions.
 
#7 ·
Ok, thanks. I'll go look at youtube for the video.
In the BGB I see 4 drain plugs in one drawing and two other AIR drain plugs under the front bonnet (radiator and heater water valve) where the 2 clear hoses are attached.

So open radiator and reservoir caps, the two drain plugs on the lower lines, drain the system, set the service hoses, refill the system, making sure the air is bleeding out.

ISpy, your comment about jacking the car up in the back while its running immediately brought to mind the scene from Ferris Bueller's Day Off when they jacked up the ferrari to run the mileage backwards by putting a brick on the gas pedal... and we all know what happened next. ;)
 
#16 ·
Considering the age of the hoses, thermostat, and water pump, I would change all of these for new. The Silicone hose kit from HPS is a really good quality set of hoses. Considering that modern coolant is good for 10-years, if you do this you will have another 10-years of not having to worry about the entire cooling system.
 
#19 ·
I believe there is a petcock valve on the block for draining. Sometimes I change something before it goes bad (coils at 130,000) but usually I wait until there is an indication an item needs replacing. I did replace the radiator at 162,000 on my 01 as it was corroded badly and leaking. I did put a new water pump on the new engine at 120,000 because it was easy and I am into this for the long term.
 
#20 ·
Phat has a point. It gets driven once a week or less. Changing the pump and thermostat are a minor deal, but replacing all thiose hoses is a pita. I would love all new hoses, but...

I'm sticking with the fluids for now. I'm gonna swap the steering fluid when I'm done with the coolant.

Carl, I don't see the petcock on the block. Must be hidden behind the exhaust manifold, visible from below the car?

Anyone have a photo or even show the item on a schematic so I can find it?

I have a question that is more technical. If the coolant system has an overflow bottle, and the top hose is above any fluid levels, how come any air in the system doesn't just circulate into the bottle, thus purging any air from the system while operating? Unless you run really low on coolant, so air could be sucked into the bottom return hose, how does it overheat after improperly changed coolant? I'm trying to picture this. Unless you get an air bubble trapped somewhere in the system at a high point, but again shouldn't it just flow into the reservoir eventually? And then you add a bit more coolant to the bottle...
 
#21 ·
That is the idea: The bubbles will circulate into the bottle and get trapped. However, if you have a big enough bubble, then it won't circulate. It will just hang out in an upper volume. That can be really bad if it is in the head or the radiator. If you get a large enough bubble in the head, then local boiling will occur and the steam pressure will block circulation.
 
#23 ·
I've done a few coolant changes and here is what I would recommend:

Drain from the front and rear. (not the middle, risk of damage to the coolant lines)
Jack up the front of the car to get the remaining coolant out from the rear.
Re-fill coolant, with the rear drivers side of the car on a jack stand.
Start the car, reach operating temp, top off coolant.
Let the car sit overnight with the coolant fill cap off (still on the 1 jack stand), run to operating temp and top off coolant again.

The service manual instructions were fine when the car was new and you were a dealer service tech with the car on a lift. The cars are old now and gravity is free. Use OEM toyota coolant. I've never had any overheating, water pump or hose failures after all these miles.
 
#25 ·
Why not just follow the proven method of refilling as stated in the shop manual? You don't even need to start the engine, just realize it can take a half-hour to fill and purge. Follow the shop manual procedure and it works perfectly every time and you will not have to worry about any large bubbles of air being trapped. I also disagree about you draining idea. It is much more effective to use the intended drains than removing the lower radiator hose.

Dave
 
#26 ·
the two coolant line drains seem to be the lowest point on the system, and the logical way to get most of the fluid out. I haven't read of anyone messing up the coolant lines doing this change. Unless you over tighten them?
Thanks everyone.
For anyone who has already done this, does any fluid come out of the the engine drain if opened? Or is it to let air into the system to make the draining quicker?
 
#27 ·
The block petcock valve is under the #4 exhaust pipe about midway on the block.

I would follow the BGB regardless of the age of the car. Personally I would use wire spring clamps like OEM if I were to change the hoses. I have thought about changing all the hoses but for now they are still in good condition. When I have a problem with one hose they will all probably be replaced.
 
#28 ·
I love those "how does it?" questions the most.
First off to level the field let's call your overflow my "expansion tank" for starters.
Coolant expands into the bottom and contracts (creates a vacuum) when cool and is sucked back into the system, like covid magic.

Your expansion tank is not meant to deal with air at all. Period.

BGB procedures are there for a reason, they work.

BTW if your operating with 25 year old rubber coolant hoses I'd think before a pressure test that a "mechanic" swears will show you a leaker.
Here's the mark1 thermo bleeder. Tool accessory

78929
Tool accessory

THE BLEEDER IS FLAWED IN THAT THE CRUCIAL ITEM IS WEAK PLASTIC.
HOWEVER, THAT ENGINE DRAIN PETCOCK HAS THE SAME THREAD AND IS ALL METAL AND CAN BE USED WITH SMALL SOCKETS.
 
#29 ·
I love those "how does it?" questions the most.
First off to level the field let's call your overflow my "expansion tank" for starters.
Coolant expands into the bottom and contracts (creates a vacuum) when cool and is sucked back into the system, like covid magic.
Mister Tim, I have to remind you again that we are talking about an entirely different car here, with an entirely different cooling system than you are familiar with. The spyder has a closed, two phase cooling system and no expansion tank at all. AND THERE IS NO TIMING BELT. :oops: :rolleyes::oops::LOL::ROFLMAO:
 
#30 ·
Just to be clear: the Spyder's fill tank is also known in the industry as a hot-bottle and definitely is supposed to have pure liquid in the lower half and air in the top. It's function is both to handle thermal expansion in the system and also to continually de-aerate the system. That is why there are small hoses going to and from the bottle. Coolant, air bubbles and steam go in the top, and only liquid coolant returns to the engine through the bottom hose. It is not an overflow tank, though if you replace the OEM tank with aftermarket, you can add one to it.

Dave
 
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