over heating issues

[CoryDerr]

We have two RFR's and mine was running at around 190-195 mid race. the twin was running at around 225. My car has roughly an inch wider radiator and my headers are coated. My question is.... how much temperature is disipated by getting the headers coated? Getting a bigger radiator isnt an option as of yet because theres body modifications needed for that. The motor was just rebuilt with 2 weekends on it. the radiators are brand new this off season as well. Any guesses?

[Brad Smith]

First check that the gauges read accurately.

[CoryDerr]

First check that the gauges read accurately.

The car that runs hot spots out some water into the bottle almost every race. How do you go about checking the gauge? Its electronic through an aim steering wheel

[stonebridge20]

The car that runs hot spots out some water into the bottle almost every race. How do you go about checking the gauge? Its electronic through an aim steering wheel

Stick a meat thermometer in the water fill and run the car to temp in the shop while comparing readings on the dash and the thermometer.
Clean the thermometer before the wife unit uses it on your thanksgiving turkey.

[Steve Davis]

If it's spitting water, then you might want to replace the rad cap as well.

[Farrout48]

The car that runs hot spots out some water into the bottle almost every race. How do you go about checking the gauge? Its electronic through an aim steering wheel

The standard AIM temp sensor is used for both water and oil temps. It is an 1/8 NPT thread. The older versions have a ~2 inch coiled wire around the electrical wire at the metallic sensor. The usual failure mode is that this electrical wire gets bent and one of the internal wires (probably the one with the resistor in it) breaks. When that happens you can get a erroneous reading which could be close to reality or way off. The more recent versions of the temp sensor have replaced the coiled wire with a stronger molded rubber support.

In a recent morning race, I saw an over-temp warning light immediately on engine start. I ignored it because it had to be in error as my oil temps have been consistently lower over several weekends and on the test day/qual. Data showed a constant 257 degrees from engine start. Consultation with Ellen Ferguson confirmed my suspicions. The afternoon race had no over-temp warning and data showed 230 - again higher than usual. Teardown when I got home showed that the wire on my older temp sensor had broken it's outer casing and the small wire inside. The coiled wire support had come loose as well.

A good ceramic coating will reduce the temperature of the headers. I doubt it will affect the overall water temperature significantly unless the temp sensor is real close to the headers. A new AIM sensor is $45.

[Jim Edmonds]

If you are spitting water into the catch bottle every session, as above, the cap is a good place to start. Next pressure test the system. Harbor Freight, or perhaps your local auto supply store, has a tester for about $90. If there is a pin hole in the system the system won't hold pressure; and the system temperature will rise during the session. A pressure tester is a good tool to keep in the race car trailer.

It will also generally test caps.

Carry lots of caps for you and your friends, Ha.

Have fun, Jim

[Art Smith]

does either car have a stainless heat shield between the exhaust and cooling system to prevent (or significantly reduce) radiant heating of the cooling system by the exhaust. cooling the engine and part of the exhaust is a tall order for any cooling system!! care is required installing a heat shield so as not to further obstruct the side pod exit (ie: further reduce the air flow through the heat exchanger).

Art
artesmith@earthlink.net

[CoryDerr]

does either car have a stainless heat shield between the exhaust and cooling system to prevent (or significantly reduce) radiant heating of the cooling system by the exhaust. cooling the engine and part of the exhaust is a tall order for any cooling system!! care is required installing a heat shield so as not to further obstruct the side pod exit (ie: further reduce the air flow through the heat exchanger).

Art
artesmith@earthlink.net

No car has a heat shield.

Another topic..... my car has ceramic coated headers. Does anyone know a rough guess of temperature difference with vs without the coating.

[Art Smith]

without regard to how many cars with 2-liter Zetecs have heat shields from the factory, a little objective thought should get you to their inherent merits for reducing the heat load on the heat exchangers................. ceramic coated primaries help but are not the total answer.

Art
artesmith@earthlink.net

[Garey Guzman]

When I got my March VFF, it had an auxiliary oil cooler used as an extra water heat exchanger, complete with a cutoff valve. Since I'm a fan of simplicity, I removed it and paid special attention to the water house routing and made some small changes to move things away from the exhaust. Haven't had a real hot race yet but no overheating so far.

As others have suggested, I'd first confirm the sensor is reading correctly but I'd also confirm that convective and radiant heat sources are shielded and that the airflow through the rad isn't restricted coming out.

[Purple Frog]

As stated before... a bad radiator cap could be the whole issue.