i replaced my engine and it has 30k on it and i replaced the entire cooling system about 2 weeks ago.. the radiator "fluidyne".. water pump.. thermistat.. ast.. and hoses... the problem i'm having is that it is pouring all the coolant into the overflow but it only does it while driving it even under no boost.. it can idle for 30 minutes or more with cool temp and no spillage... it's not blowing any smoke and it runs perfect up until i drive it, then the coolant dumps and then it starts to over heat.. what could this be cause from??.. i heard that if the o-ring goes you blow smoke.. so i'm preying that isnt the problem.

'94 rx7
touring
no mods

 

Here's the deal: If you have the overflow tank level allll the way to the top, then any expansion of the coolant will cause coolant to come out of the overflow bottle. If your coolant level is at the F mark and you overflow while driving, suspect the O-rings. More so, if you have overflow from the tank, AND you are constantly having to top off the coolant level at the filler neck, AND you are sure you have no leaking hoses, then really suspect the O-rings.

But you are showing a CLASSIC sign of blown O-ring in that you only get overflow and overheat WHILE DRIVING, that is, when the rpms are high enough to force combustion gasses into the cooling system. As my rings were failing, if I was real light on the throttle or drove only a short didtance, I'd lose very little coolant. If I reefed on it, I lost plenty of coolant. It was going into the overflow every time.

Do the bubble test. Put a pressure tester on the system. But this really sounds like a not so fun problem.... Sorry!!!

 

thanks alot for your reply... i planned on doing a pressure test on it as soon as i had some extra time.. if i come to findout there isnt a lose of pressure can you maybe think of the next thing to check for?.. thanks again

 

Well, if you are holding pressure, then you can rule out leaks in the system that are causing the coolant to not be drawn back into the system. But again, that only happens when the engine is cooling down (about 20 minutes after shutoff). You are having overflow while running, sooo....

You should do the bubble test at the filler neck. I stuck a plastic 7-Up bottle that I cut the bottom off of into the filler neck and had the girlfriend start the engine. I did this with the coolant about 2 inches below the full point on the filler neck. The coolant immediately expanded into the plastic bottle (which was in fact acting as a funnel, but that sealed better to the filler neck than any other funnel I had), mostly from the pressure from the water pump. Then, as I revved the engine over 1500 rpm, a frothy bubbling showed up in the coolant in the bottle. Awwww.....

You can also take it to a shop that can test for unburned hydrocarbons. They can "sniff" your coolant at the filler neck to see if there are exhaust gasses in the coolant.

Some folks say the plugs will be wet if you pull them, but mine were bone dry. I had smoke coming out the tail pipe at startup. It wasn't real extreme, just a little thicker than you might expect to see from a car warming up on a cold morning. Of course, it would smoke even if it was 50F outside, which it shouldn't really do. My O-rings were just starting to fail, though.

I will say that I did try putting a hose on the overflow nipple on the AST (the nipple under the cap next to the battery) and ran that into a bottle half filled with coolant. Normally, there should be no flow of coolant into that bottle until the engine reaches around 200F, but I was getting flow out the AST almost immediatly. Again, this was due to O-ring failure...

 

thanks again for your reply... i just have one more question.. is the frothy bubbles an indecator of a blown o-ring also?

 

yep.

 

also you can check the hose that goes from your radiator to the overflow tank. make sure that isnt damaged or at an akward angle. a few times i had it going around my IC pipes in a weird way and it would make it continuously suck in or blow out coolant. prolly not your problem, but an easy check.

 

Shes cooked man.

 

im with pancho

 

is the only way to fix a blown o-ring to either rebuild or replace the engine?

 

Yep, if you want to do it right.