Caterham Crossflow Running Hot

[plbs1234]

I am continuing to work on Pandora (Caterham Series 3) trying to have it reliable for road trips.

 

I've sorted out my electrical problems, got the emissions to a low enough level to pass the state emissions test, added an electric fuel pump to solve the vapor lock problems I was experiencing, and have the Weber DCOE 40's adjusted so the car is running well.

 

Took it out for a test drive today and all was well until I hit the interstate and drove at 75 mph. At speed the coolant gauge climbed until it was reading about 225 degrees. Running a 50/50 water antifreeze mixture with a 7 pound radiator cap. When I pulled over the coolant in the overflow bottle was actively boiling. I assume that as the coolant expanded and vented to the overflow bottle at atmospheric pressure it was hot enough to boil.

 

I calculate that the boiling point of the coolant in the radiator under pressure is about 240 degrees.

 

My question is, will running at 225 to 230 degrees coolant temp hurt the engine? Is this temperature normal when the car is being pushed hard?

 

The thermostat is new and as part of passing emissions I had a valve job done so the head gasket is new and the head was surfaced and is newly torqued.

 

When I slowed down after getting off the highway the coolant temp returned to normal range, although it took longer than I would have expected.

 

Any suggestions?

 

Thank you.

 

Paul

[xcarguy]

Paul,

 

Unless it's the norm for the crossflow coolant system, a 7 psi cap seems like a very low pressure cap. I use a 21-25 psi cap for my Stalker's coolant system and can run in the 230F range when on track (pushing the car hard) with no coolant issues. To help put this in perspective, I was running an 18 psi cap prior to the 21-25 psi cap and my car would consistently run hot (puke coolant) above 210F. 210F is a normal coolant temp for an aluminum LS engine, however, my engine will consistently run 180F on the highway under normal driving conditions. While I'm comparing apples to oranges concerning cars and power plants, physics be physics when it comes to temp and pressure. You might want to rethink the 7 psi cap. My two cents.

 

Another consideration; if you have recently changed the coolant (assuming you did because of the valve job) did you get all the air pockets out of the system? If not, this will only compound the high temp/overflow issue.

 

Also, might be some useful info in this thread:

 

http://www.usa7s.net/vb/showthread.php?t=9719

 

. . . . . :cheers:

Edited June 26, 2014 by xcarguy

[Kitcat]

See the active thread "Caterham running hot" at the tech section of this forum. My Caterham X-flow did what yours is doing when I had air pockets in the cooling system. Once burped, it ran all day, even on hot summer days, at 75-80 mph on the interstates. Of course the driver overheated, but that's a different discussion:).

[bball7754]

That seems hot to me. 7 PSI is definitely too low. Believe the "standard" cap is 14.

 

I've been wrestling with coolant filling my catch tank since I've had my Xflow rebuilt. Just finished converting it to a sealed system.

 

Steve

[plbs1234]

Thank you for all the reply's and thoughts. After reading the suggested threads and doing a search on the site for overheating I became concerned I might have a head gasket problem or even a cracked head. I see no coolant in the oil and no bubbles in the radiator.

 

I contacted the shop that did the valve job and they said they ran a pressure test on the head and everything checked out OK. To rule out cracks or the new head gasket being blown I ran a radiator test for combustion products using a Belkamp Fluid Block Leak Tester. I never got any change in the fluid color so apparently I'm not leaking from the engine combustion areas into the water jacket.

 

I upped the radiator cap to a 16 pound unit and added waterwetter to the radiator.

 

When the engine was up to temperature I drained enough coolant out to actually see the thermostat and it was wide open.

 

At this point I should be OK with the higher pressure cap and keeping a close eye on the temp gauge. My next step will be to switch to Evans Waterless Coolant. This will eliminate any boil-over and hopefully give some improved cooling, especially in the engine hot spots where the existing coolant may be vaporizing locally.

 

We're just getting to the really hot (100 degrees +) weather here in Idaho. I'll be interested to see how the cooling system works at the higher temps. Only other thing I can think to try is going to a higher performance radiator for improved cooling.

 

Thanks again for the help.

 

Best regards,

 

Paul

[coffee break]

Do you know the history of the car? I'm wondering if the radiator may have some clogged passages from old coolant. I had to rebuilt a motor because of a plugged up rad.

Good luck.