[jasonxh]

Hey guys I just bought an '87 3rd gen prelude last week and I've flushed the coolant like 10-15 times already. Last night I did another total flush with plain water (drain, refilled, bled with the bleed valve, ran the engine with heater on, waited to cool, drained it again, loosened bleed valve). It came out like this

Which I was told was quite clear. I refilled it completely with water and left it overnight. In the morning I started the engine for about a minute just to reverse out of the garage before turning it off. I opened the bottom of the radiator and drained it where it looked even clearer. However, when I opened the radiator cap, more water came out and it looked like this:

It's rusty and dirty even though I've done at least 10 flushes. After that, I loosened the bleed valve, at which point it became clear again. My question is why does extra water come out the bottom of the radiator when I loosen the cap on top? Is there some sort of weird pressurisation thing happening? Where does it come from? I only ran the engine for less than a minute. If I can figure out where this water comes from I'll be able to figure out where my rust is. Thanks everyone.

 

[Stub]

1. 87 prelude is 2nd gen
2. Tap water will cause rust. The process is accelerated with heat. If you want to flush a system, use distilled water and radiator flush product or CLR.
3. Simply opening the drain plug on the radiator won't get all the water out. If you open the heater valve all the way, then detach a hose and blow in air with an air compressor that should push the rest of the water out.
4. Its difficult to get all of the rust and other impurities out of the system. I've removed coolant hoses where rust flakes were stuck to the inner tube. I cleaned out the valve for the heater core once and I had to open/close the valve like 100 times while running water through to get all the crap stuck in it completely out.

 

[Rollthelosingdice]

Flush it with vinegar.

 

[jasonxh]

1. 87 prelude is 2nd gen
2. Tap water will cause rust. The process is accelerated with heat. If you want to flush a system, use distilled water and radiator flush product or CLR.
3. Simply opening the drain plug on the radiator won't get all the water out. If you open the heater valve all the way, then detach a hose and blow in air with an air compressor that should push the rest of the water out.
4. Its difficult to get all of the rust and other impurities out of the system. I've removed coolant hoses where rust flakes were stuck to the inner tube. I cleaned out the valve for the heater core once and I had to open/close the valve like 100 times while running water through to get all the crap stuck in it completely out.

Thanks for the advice!

Also my prelude is definitely 3rd gen. Pretty sure 3rd gens were released in 1987 in Japan but the US only got the 1988 models. I'm in Australia.

 

[blazeaglory420]

Thanks for the advice!

Also my prelude is definitely 3rd gen. Pretty sure 3rd gens were released in 1987 in Japan but the US only got the 1988 models. I'm in Australia.

Released in April - November of 1987 around the world would be an 88'. Unless im totally wrong and there's actually a 1987 3rd gen,(that was released towards the end of 86' lol)

What im saying is just because it was released in 1987 doesn't make it a 1987 model

 

[luzer]

I remember reading that JDM models were 1 year ahead of USDM models. JDM 3rd gens were 87-90, while USDM 3rd gens were 88-91.

 

[Sam91]

I remember reading that JDM models were 1 year ahead of USDM models. JDM 3rd gens were 87-90, while USDM 3rd gens were 88-91.

That sounds right. In the Gran Turismo video games a 1991 Honda prelude is a 4th gen. I wish they would have a 3rd gen but they never do.

 

[1funryd]

Just call it an 88. Saying 87 will just confuse people and have people doubt what you are talking about.
This chassis is hard enough to support since its already a bastard child of Honda.

But to your rust issue, you are also not completely heat cycling the entire engine. The thermostat is not opening up so you will have rust trapped in many areas of the motor.

remove the thermostat open the lower radiator hose into a bucket and the get a pressurized air line nozzel that hooks up to a water hose and flush the system that way.
I will be the cheapest way to flush the entire system.
open the heater valve while doing this to ensure you flush that part as well, as it will have trapped rusty water in it as well.

Other than that process, removing the motor and doing a complete tear down is the only other way to clean out everything.