Looking for some ideas on an overheating gremlin. Chased it for awhile and finally lost the head gasket. Any thoughts on what to check are appreciated:

Rebuilt '88 2.5L, including new waterpump. First start for 10 minutes and temp went to 220. Rechecked everything and same result. Using Evans NPG-R waterless and pressure-less coolant http://www.evanscooling.com/coolants/

Spent 1 hour on dyno for break in, A/F was good. Temps were high again, but with the hood up and 3 fans on the engine/radiator it stayed around 220-230.

On track for test and tune 4 times - 2 to 3 laps each time. When I kept RPMs low I would see 230, if I took it to 5-5.5K it would go to 250.

Changed the thermostat, installed a belly plate under the radiator and bumper cover, hardwired both stock cooling fans, and drilled three 4" holes in the bumper cover above the already open area. Bled system at every opportunity, including with front end jacked up, and jacking up only one side at a time.

Top and bottom radiator hoses were both hot.

Back out on track for 3 or 4 laps, kept RPMs under 5K and temps went to 230 or so. Came in and bled the system again. Let engine cool for awhile and went back out.

First lap showed 220 at lower RPMs, next lap at 5K showed about 230, next lap at 6K showed 245. Decided to call it quits but a few corners later I lost the head gasket.

Coolant comes out tailpipe and was also in the engine bay, but hoses, etc. are in good shape. The coolant system is pressure-less because of the Evans NPG-R.

Have an Autometer water temp gauge and factory gauge - both showed the high temps.

Never had cooling issues with prior motor.

Heard radiator fins can expand stopping airflow but still allowing fluid flow. Will install a turbo radiator.

Any ideas on what else to check? Thanks.

Is the shrouding around the radiator intact? So the airflow can't spill around.

What is the history of the radiator?

On my car (2.5 NA new turbo radiator) the factory fans will pull enough air through at idle to keep temps at 180 regardless of how the intake side of the radiator is boxed in. 220 after 10 minutes at idle is your benchmark for a problem regardless of what happens at speed.

It also sounds like you've bled air a lot. I pressure bleed once and never have to touch it again.

Steve

Radiator?

Thanks guys. Radiator was fine before new engine and seems to flow ok. Will be replacing with a new turbo radiator.

Suggest , checking the block deck, is it straight? Cylinder head , get it pressure tested for a crack. Radiator , more than likely its ok. Engine is building up heat from lack of flow. Cylinder pressure is retarting flow, head gasket is not sealing, warped block deck, or cracked head , right off the get go. Also , what octane and compression does the engine have/get?

Thanks Ernie.

Stock '88 compression - measured 10.1.

93 octane pump gas (Georgia).

Block and head decked during rebuild.

Head will go to machine shop for pressure test and will check block deck. Will also check torque before disassembly for bolt stretch.

Any other things to check for during disassembly? What signs can I look for regarding cylinder pressure retarding flow?

Thanks.

Ernie, doesn't that make the head gasket deform in the areas between cylinders where the water jackets are?

Was the water pump new or a reman? I had tons of cooling issues with the 88 engine in my car years ago, but not as severe as what you had. Sure does seem like a sealing issue, but I would think that the coolant tank would have popped first. Many of the inexpensive reman pumps do not have the correct clearances and will not move enough water. From your description I suspect a crack in the head but you dont mention water loss in your account.
In my case it was more to do with the oil temp causing the water temp to rise. A 951 cooler setup amd a 951 radiator put everything right. Water temps under 200f on 80f day, oil temps 225 to 240. Greg F

Greg, thanks for the ideas.

Water pump is new. No loss of coolant prior to losing head gasket.

On the coolant tank, the cooling system is not pressurized with the Evans NPG-R fluid. That's why the coolant in the engine bay is confusing - understand a blown head gasket would leak into the cylinder but there is no pressure to cause coolant to blow into the engine bay.

I'm using the 951 oil cooler console with a Setrab remote cooler.

Thought I had done everything right after my last engine lasted 12 hours . . .