Overheating issue
 

I have an overheating problem that I have been told is due to my radiator. I currently have the CX-Racing aluminum radiator (EBay radiator), with the M-Tuned water reroute, and an oil cooler. I am running a GT30 at 21psi and still have water being pushed into the reservoir after several dyno pulls. The other reason I have been given for the overheating was a blown head gasket but a compression test indicated good compression in all cylinders. Is it time to get a new radiator or could there be something else causing the trouble?

This issue has been discussed comprehensively at least 3 times in threads that all have posts as recently as the last 7 days. You're not going to get any help without a much more substantial explaination on how you've addressed the problems and solutions posted in those recent threads.

Also, consider that you have little to no airflow through the radiator during consecutive dyno pulls. Anyone with any amount of expertise will argue that you have no problem whatsoever with your cooling system. A dyno will do a very good job at simulating load on the engine, but it will do a horrible job at simulating airflow across the heat exchangers regardless of what type of high flow fan system you have setup at the front of your car. Your cars cooling system is designed to actually move through air, and the entire engine bay acts as a low pressure zone drawing air in through the heat exchangers. Consider that a low pressure zone in the engine bay acts MUCH more effectively at moving air through the heat exhangers than a high pressure zone in front of the engine bay.

With regard to possible head gasket failure: A compression test will ABSOLUTELY NOT give you any good information on the status of your head gasket. Consider that, during a compression test, your cylinders are seeing atmospheric air pressure, and then compressing that air 8 or 9 or 10 to 1. (14+0)*10=140psi

At 21psi, you're seeing 2.5 bar, (or 2.5 atmospheres) worth of air pressure being shoved into the cylinder, and compressed. (14+21)*10=350psi

Now take that 350psi, and add a violent explosion to the mix.

There is, however, a way to tell if you have a head gasket failure. At normal operating temperature, with an ideal coolant system (no air pocket) hit full boost for a couple seconds. If you're blowing air through the coolant expansion tank, you have a problem. If you're only blowing water into the coolant expansion tank, and you have no air in your radiator afterwards, then you don't have a problem. I'm going to assume you know that coolant expands when it gets hot, and your system requires more volume to hold the same amount of coolant - that's the reason you have that extra coolant tank there.

Yea I am thinking air is getting blown out since it is being shot out of my coolant tank. I just had the motor built less than 1,500k miles ago by AMS so I really hate to think it is a head gasket.

I've actually seen a blown head gasket on a turbo car cause the filler neck to bend so that the cap wouldn't reseal properly. It will put lots of pressure in your cooling system quickly under a high boost load. And the compression test showed no real variation between cylinders.

It happens.

Edit: I suggest head studs in addition to a proper head torque procedure might be a good idea when you change the head gasket. The stock Mazda gaskets have a good reputation and some of the aftermarket ones don't. I don't know which ones offhand.

We used a Cometic metal headgasket and ARP head studs. Now they are telling me the overheating is caused by either my ebay radiator or a broken head gasket. And want to charge me 1100 to replace my head gasket that they installed 1500 miles ago.

ARP hardware will make it easier to re-install the head+gasket. Highly recommend using a mazda MLS gasket, there's also another company that makes a decent gasket, cant think of the name off hand, might be "cometec"?

Double check to make sure your head bolts are torqued to spec before taking the head off

1: It's not your radiator
2: Get a lawyer involved
3: Never use that shop again

Was head re-torqued after being driven? Some head gasket manufacturers require it in their installation instructions.

Don't go back to them unless they are re-doing it for free. A good shop would change a head gasket for half that price, so I know they are fucking you. Demand better.