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I'll introduce myself with a dilemma I face.

Just bought an 1990 NA.

Rebuilt motor 25,000

Figured I better do a fluids change, Oil, Transmission and Rad

So. I Noticed a few particles of rust/something in my rad when I took the cap off, I figured it was just from the cap that had deteriorated.


Ran some rad flush through the cooling for 10mins but the water kept coming out brown.

I then took the inline thermostat housing off the top silicon hose, put my finger into the hose and..


..then I noticed a spring in the hose, I pulled that out, along with a metric sh!t-ton of rust.


Ive flushed the engine out with the hose, the water comes out clear at the other end.

I spent >20 minutes running the hose though the Rad, and brown water continues to come out (brown rust sludge blobs came before)


Last night I did spend another 10 more minutess it began to get clearer.

Before all this the car had no indication of an cooling issues/didn't over heat.

What course of Action should I take?

(my plan: continue to flush radiator until clear, purchase more Radiator flush and run that through again..)

I'm semi-worried the waterpump could be damaged and primed to fail in the future..

Anyone have an idea as to why the spring in the top Radiator pipe corroded so quickly?
Can I run the cooling without a spring, without the pipe collapsing?

Cheers.

Plan A is to keep on doing what you're doing: sh*tloads of cleaner and flushing through the whole system (not just the rad) will get almost all of it. Remove the thermostat and get creative with hooking up garden hoses to various hoses. I've taken 2 or 3 kilos of rust out of the heater core alone in one BP Mazda. I used about 3000 litres of water to fix that car and it went OK for years after that.

The idle air valve on the inlet manifold is really good at trapping rust in the coolant. If you still have idling problems after all the cleaning then you'll have to pull it off, clean the rust out and maybe replace all the blocked little hoses around it. http://www.miata.net/garage/isc.html

I wouldn't worry too much about other problems yet other than just a check on the condition of all hoses and fittings. Nearly all of the rust originates from inside the engine block and losing metal there generally doesn't do much harm.

I'd suggest the spring rusted from being in contact with water.

All the hoses I've seen have never had anything in contact with coolant other than the rubber they're made out of, any reenforcing material (be it metal coils, fabric mesh, whatever) should be encased inside the rubber.

The easiest answer is to replace that hose, it should cost all of $20 or something for one hose.



As for the rust, it sounds like somebody in the past has run the engine on plain water.
The best you can do is give it a flush, replace the thermostat, and budget for maybe needing a new waterpump in future (the flushing is likely to loosen up gunk that might clog the pump)


I'd also do a better flush, put the radiator flush in, run the engine for a while to get up to full temp (you want the thermostat to open fully to circulate the flush around, even better, remove the thermostat) and also have the heater on full (clean out the heater core)
Then drain the coolant.

Once it's cooled use the hose to flush the radiator, and also consider flushing the engine (hose down the waterneck)


You'll never clean out every nook and cranny, so don't be too concerned about the water being 100% clean at the end.

manga_blue wrote:The idle air valve on the inlet manifold is really good at trapping rust in the coolant. If you still have idling problems after all the cleaning then you'll have to pull it off, clean the rust out and maybe replace all the blocked little hoses around it. http://www.miata.net/garage/isc.html
.

I'm not as to whether I have an ISV due to the ITB setup, the small hose coming off the old thermostat housing feels crusted with rust particles, all the silicon houses have their insides caked in rust, will have to acquire a bottle brush to clean them.





I think I might try and remove the heater core and flush it out, outside the car, wish I could remove it altogether but Canberra winter..is coming.

As for removing the thermostat, the two halves of the inline thermostat housing are mated together with some atomic bond, aha. I don't have vice grips or anything big enough to turn them..


Thanks for the replies,

FrontLever wrote:I think I might try and remove the heater core and flush it out, outside the car, wish I could remove it altogether but Canberra winter..is coming.

It's all looking depressingly familiar. Removing the heater core is a major job and there's no need to do it at all in order to clean it out. Just take off the two hoses that connect to it at the firewall just behind the exhaust manifold. If they're at all tight to get off then you must cut them away and replace them, otherwise you'll break the brittle copper pipes going into the core. Then connect a garden hose to each copper pipe and run the water for a few minutes several times in each direction until it runs perfectly clean.

With that much scale rust in the system you will have to replace all the little hoses - they'll be choked. No need to buy special ones, just get lengths of right diameter hose from bulk at Repco.

Your major issue is all the scale that you can't see that has built up inside the head and block. If it stays there then it creates hot spots which can warp or crack the engine. That's why you've got to do to the engine what you're doing to the radiator and heater cores - flush it every which way you can. There's nothing difficult about any of this - it's just tedious work with the garden hoses.

manga_blue wrote:Your major issue is all the scale that you can't see that has built up inside the head and block. If it stays there then it creates hot spots which can warp or crack the engine. That's why you've got to do to the engine what you're doing to the radiator and heater cores - flush it every which way you can. There's nothing difficult about any of this - it's just tedious work with the garden hoses.

Hopefully though, since it's apparently a rebuilt engine with 25,000km on it it shouldn't be that bad.

Of course, I'm assuming here that the block was pulled down and properly cleaned out (acid dip or something)..... if it was just given a new set of rings.... well....



I agree with Manga, flush it every direction you can to try and dislodge it all.

Manga_blue wrote: Just take off the two hoses that connect to it at the firewall just behind the exhaust manifold. If they're at all tight to get off then you must cut them away and replace them, otherwise you'll break the brittle copper pipes going into the core. Then connect a garden hose to each copper pipe and run the water for a few minutes several times in each direction until it runs perfectly clean.

Yeah, I decided against such an operation and did exactly that, didn't take much to flush clear, here's hoping that's a good sigh.. The only small hose, I replaced.

hks_kansei wrote:Hopefully though, since it's apparently a rebuilt engine with 25,000km on it it shouldn't be that bad.

It's Yuge's old 1.7, I have $5000+ in receipts for the rebuild, I'd hope nothing was skipped..

Ran some Rad flush through and am leaving it to sit for the night (sorry, neighbours was starting car up at this time )

My MX5, 1995 1.8 has been having problems with the overheating too.

I figured it was a a good idea to replace the hoses, and found the same rust and scale in the heater hoses.

Manga blue I like your approach to things, are you a professional mechanic?

Engine didn't take long to flush clear, the radiator took the most time, I replaced the thermostat, put new coolant, she's running just fine, well she was before this but ya, no rust is good!

maroubra wrote:My MX5, 1995 1.8 has been having problems with the overheating too.

I figured it was a a good idea to replace the hoses, and found the same rust and scale in the heater hoses.

Manga blue I like your approach to things, are you a professional mechanic?

No, I'm pretty sure he is not. All that rust in the coolant will settle in the radiator and the heater core. All the other coolant passages in the engine are large enough for rust to pass through easily.

There aren't really any small hoses, unless you have the iscv instead of an IAC. But even the smallest coolant hoses are large enough for ruat speaks to run through.

Plus rust won't cause hot spots in an engine. Rust is very terrible at holding onto heat and will break down if over heated. There is no way in had some tiny that piece is going to throw off the cooling balance of the system.

Some people overthink things. His advice is not bad or damaging, just the reasoning is flawed.

If you see a lot of rust my suspect would be the steel water pump impeller, not the aluminum block or copper heat exchangers.

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higgimonster wrote:see a lot of rust my suspect would be the steel water pump impeller, not the aluminum block or copper heat exchangers.

I would actually say the most likely would be the block.

Which is Iron, not aluminium.