High RPM cooling issue

[CrashGNX]

If I run the car at a high rpm I get bad aeration or maybe even cavitation (small air bubbles) in the coolant, I can watch it with the cap off and funnel with some water in it on the t-stat housing. above about 4k rpm the coolant goes from clear or slightly green to murky white until I let off the throttle and it settles letting the air back out of the water. I ran it hard on and off for about 20 minutes around the backroads and when I got home the coolant was steaming out of the overflow and it had basically boiled close to all the water out of the system.

I have a massive radiator, plenty of airflow through it, and an otherwise well running setup. I am going to try swapping the water with distilled water and some water wetter and see if that helps it any.

Best I can figure is either cavitation from the water pump or hot spots in the head causing water to boil off the internal surfaces. air coming out of the water does not smell anything like exhaust so im pretty sure the head gasket is intact, I just replaced the rad cap and I know the 180 deg thermostat is in working order. Idle and cruise speeds rarely even get the water to operating temp of 160deg and autocross runs dont usually get it above 200 after 5 or 6 runs but it does push quite a bit of coolant into the overflow.

Any ideas what would cause this? I know a few other road racers have had similar issues but I have not seen anyone post that they actually solved the issue for sure.

 

[ACM]

If you are pushing out enough coolant to fill the overflow just on back roads, it's a failed head gasket. If you have an air compressor you can confirm this by doing a leak down test, but in reality your symptoms scream blown head gasket, I wouldn't even bother checking further.

Since your head gasket has failed, be sure to check the block surface for warpage - there's nothing more annoying than replacing the HG only to find the new one leaks because the block's warped ! If you don't have a good straight-edge to check the block, the shop that skims your head will be able to create/loan/sell you one for very little money. Fixing a warped block is a PITA, but it beats changing head gaskets every weekend as you chase your tail...

 

[CrashGNX]

If you are pushing out enough coolant to fill the overflow just on back roads, it's a failed head gasket. If you have an air compressor you can confirm this by doing a leak down test, but in reality your symptoms scream blown head gasket, I wouldn't even bother checking further.

Since your head gasket has failed, be sure to check the block surface for warpage - there's nothing more annoying than replacing the HG only to find the new one leaks because the block's warped ! If you don't have a good straight-edge to check the block, the shop that skims your head will be able to create/loan/sell you one for very little money. Fixing a warped block is a PITA, but it beats changing head gaskets every weekend as you chase your tail...

I changed the water to distillied and a bottle of water wetter, it helped but still over headed with same issue on track, yeah im agreeing with you as it it is most likely a seeping head gasket. I'll swap it out this winter after autocross season is over. Thanks for the reply.

 

[TAMA_player]

I had this issue in the past. Very small bubles on the coolant. Not rpm related but at boost. We changed the head gasket for a metal multilayer and the issue was gone. 5 years on the same gasket with no issues. Just to confirm what ACM posted.

 

[AllanL]

if it were the HG, with the radiator cap off, wouldn't water flow out the radiator cap filling port during the first crank after the car has sat for a while?

 

[CrashGNX]

Definitely was the head gasket, pulled it and found it was blown in 4 places . between 1-2 between 3-4 between 1 and the water jacket, and 2 and the waterjacket. Also found damage from debris of somekind that had gotten into all cylinders and left dents in the head and pistons. #1 rod is also probably bent slightly, the reveal on #1 is about 1/8 inch below the deck and the rest are flush with the deck. Also there were dents in the pistons from the valves. I cleaned up what I could of the debris and valve damage to eliminate hot spots and put it back together with a new felpro gasket and ARP studs. What can I say I had to get it running for the next track weekend .

I ran an autocross weekend and a full track weekend on it and had 0 issues with anything major. I ran it out of gas twice and killed a nearly new set of HAWK HPS pads down to the steels. Also the dipstick defeated its hold down and popped out but was easily remedied with adjustment to the hold down. I am modifying a valve cover currently with a 10 AN fitting to relieve the block pressure of this tired old motor.

When I got the JDM red-top engine it still had the cyclone intake attatched and as far as I knew the valve cover had never been off let alone the head but I was sadly wrong, I could tell the head had been off before, there were scoring marks on the gasket surface from someone banging it on the dowels. The head bolts were not uniformly torqued either, a few were pretty loose compared to the others.

I'll start saving to send another of my engines out to JAM to get built and swap it out eventually. Right now it obviously does not make enough power to finish off anything that is currently damaged in the bottom end, I run the holy crap out of this thing on track.