Could be a result of electrolysis causing some corrosion. I'd be tempted to drop, flush and replace coolant.

Jim

 

+1 Some of the coolant lines do corrode out. The bypass line will and the water neck that has the hose that connects to the plastic piece with the radiator cap will rust. I'd had a piece of that actually rust off and find it's way into the system.

If I were to rebuild my engine again I'd get these pieces chrome plated to help protect against it.

 

[Posted in wrong thread]

 

Anytime you have diffferent metals with fluid running through it will form a battery (anode-cathode). The material which is more reactive will give up electrons to the other (electroylsis). This results in corrosion of the sacrificial metal.

The MR2 has long coolant tubes with many different metals in contact with fluid including, stainless, aluminium, copper, brass, iron and cast iron. If the PH of the coolant is acidic then it will transport the electrons from one metal to another. This is why it is recommended to change the coolant every maintenance period. The glycol (anti-freeze) which raises the boiling and lowers freezing point doesn't wear out.

The metal in the coolant is an indicator that the electrolysis is taking place. Best to drop, flush until system is clean then replace with decent 50/50 mix antifreeze. I add a bottle of corrosion inhibitor (soda ash) to correct acidic PH every year or so. Don't know if you can do this with the red Toyota brand which is why I don't use.

Good article about coolant types if you care to read. It's probably the most neglected fluid in our cars.

http://motorage.search-autoparts.co...autoparts.com/motorage/data/articlestandard//motorage/162005/156227/article.pdf

jim

 

Thanks Jim for the replies. I was thinking of electrolysis, I found a website that shows how to test for it in the coolant. What it states that most likely the electrolysis is caused by a band ground. So I plan on going through and double checking the engine grounds and some other electronical components I installed. I'm still a little puzzled on why so much coolant was pushed out into the overflow tank. When I checked my coolant level, there was zero coolant in the water neck. So I plan on doing a thorough flush, replace the radiator cap and possibly the thermostat. Just curious what's the best way to flush the coolant?

 

i'd say someone put stop leak in there at some point in time otherwise with electrolysis you really won't see the particles.

other guess would be water pump crapping out

 

Hey Josh, I appreciate your two cents on the matter. The most likely thing I can think of is a po used stop leak or alumiseal at some point. I couldn't imagine my water pump is failing, I mean you replaced it less than a year ago and it only has less than 1000 miles on it. But one never knows, there's always a chance. Regardless, I'm going to flush the system anyways.

The awesome metal flake/granules/particles that are in my coolant:

 

For sure looks like stop leak

 

I'd agree, not from corrosion.

 

I also faced this issue on my Seat Cordoba when engine temperature exceeded 100 degrees. There was some kind of shining metal parts inside the coolant reservoir. A faulty thermostat has caused this problem, it has a metal alloy on the tip and it was melted due to high temperature.

 

If there jas ever been radiator stop leak in either your vehicle or donor engine vehicle you'll see that metal flake.... it's nothing to worry about