XLR8BYU

Hello memebers. My car developed a wierd issue on the drive up to Carlisle. While driving up, under any sort of load, my temp would very quickly jump up to 250ish. I pulled over to let it cool, and found that if I kept the rpms under 1500 it would cool down and stay between 230-240. While sitting at a redlight at idle, it would cool down to normal.

Replaced the thermostat while at Carlisle and made sure to have the computer turn the fans on earlier. While cruising around the fairgrounds and in the traffic jam leaving, the temp stayed at 190-210.
Once we got out of traffic and started normal driving, temp rose to 240-250 in a bout 15 minutes. Again, if I stayed under 1500 rpms it would drop back to 230-240.

Anyone have any ideas? Been doing a search and haven't found this problem.

Papas02C5

Sounds like possibly your water pump impeller isn't quite up to the task anymore. How many miles do you have on the car?..

XLR8BYU

45k miles on a 2004

AU N EGL

When did you last or have you ever cleaned out the radiator and ac condensor?


Dirt and grass will get stuck up there. and you wont see it until you clean it.

CHJ In Virginia

Garbage in the condenser and radiator is usually your primary cause of overheating. Blow it out with compressed air. There are several threads on the process, it's not hard. I would also check for a radiator hose that is collapsing, have seen several that were delaminating on the inside of the hose blocking flow.

XLR8BYU

Why would it only impact the temperature while under acceleration and not while sitting at idle or in stop and go traffic?

AU N EGL

Lets not worry about the WHY this or WHY that. Clean out your radiator and AC condenser with a air hose. Go in from both sided.

XLR8BYU

Will do. Thanks for your help.

Evil-Twin

Fans turn off at highway speeds, leaving only flow through air circulation to exchange heat, at low speeds the fans are on and help force air through your partially clogged radiator and ac condenser.. clean then both out, best way is from the back toward the front of the car... the radiator sits behind the ac condenser, so if either is clogged you will have a problem..its best if you remove the top radiator shroud , 4 bolts... then clean out the ac condenser using a long wand and an air compressor.. once you clean out the condenser..put a piece of cardboard to protect the condenser from being clogged again with debris from the radiator as you clean it... you can use a long brush too.. they sell dryer brushes at home depot to clean out your clothes dryer vent.

baxsom

any chance that when you changed the thermostat that air got in the system?

XLR8BYU

The issue started before I changed the T-stat. Going to clean everyting out first.

SB99NassauBM

Clogged fuel filter was causing my 99 to get hot. It was running lean,changed it out and everything went back to normal.

BTW this was with Dewitts radiator and reprogrammed fans.

redroket

Replace your water pump. I had the same problem. blew everything out changed this and that and it was the water pump!
Go for it!

fevest

Is your air dam in place? It directs air through the thing at highway speed.

XLR8BYU

****UPDATE******
Blew air in both sides cleaned out debris from blocking radiator....
Started car cold and ran for 15 mins. Temp = 173

Drove car around neighborhood (under 25 miles an hour and 2000 rpm) temp went to 190.

Drove car around for 15 more minutes on normal roads, and a 4 lane highway. Full range of speeds and RPMs. No hard acceleration, shifting between 2500-3000 rpm. Car temp increased from 190-245!!!!

I know this isn't overheating, but with a 160 thermostat and reprogramed fans on a 75 degree evening, something is wrong.

Drove back to house, let idle for another 15 minutes and the temp dropped from 245 to 205.

Why is my car getting so warm, so quick under driving conditions?
Clogged radiator? Waterpump? Need help guys

toddk

Any changes in mileage recently since the problem was noted, for the better or worse? Performing like it always did? Any coolant consumption or oil contamination? Does the coolant overflow at 245, or is pressure retained?

I don't think an engine produces nearly as much heat as when it's under load. My wife's little 4-cyl would barely keep warm idling in the deep of winter. I'm guessing internal flow blockage somewhere, perhaps a vane broke off the pump? Or if you were ever low on coolant, I've had Dexcool gunk up the block pretty bad. Maybe a coolant flush is in order.

Todd

thechosenone

I agree, go the cheapest route first I would say water pump last. Flush your whole system then fill it back up and make sure no air is in it, just use distilled water at first to see if the flush helped at all. No point in wasting money on coolant till you find the problem out.

toddk

It think it all boils down to lack of flow, lack of pressure, or combustion gasses overheating the coolant. A few (cheap) tests are warranted to narrow it down. A combustion gas-in-the-coolant test will check head gasket integrity. A coolant pressure test (& new GM cap) will ensure your system can hold 15+PSI. A coolant flush may provide some insight. After that you (or trusted mechanic) need to tear into it and rule things out. Pump failure, radiator blockage, block blockage.

Distilled water won't make it to 245 degrees without boiling like the 50/50 mix will, so the test would be short-lived and you risk head warpage/damage. The car also wouldn't be driveable to a mechanic like it is now.

"Flush" is not a DIY drain & fill that leaves the thermostat closed and the block full of old coolant. A flush gets the engine to temp, and swaps ALL the coolant using a specialized machine designed for the task.

Ideally an in-line coolant flow gauge you could place in the top hose should tell you if there is circulation once the thermostat opens. I didn't find any cheap ones at the parts stores. If the flush machine has a flow gauge, or if the reservoir for the old coolant doesn't fill fast as "normal", you may get a blockage answer from that.

One other pump test. Does your car put out hot air with blower on high, or does it gradually get cooler? I know that's hard to tell during summer. The flow thru the heater core is not governed by the thermostat and is always open. If the pump is not flowing adequately, the heater core will cool down quickly rather than staying hot.

Todd

XLR8BYU

****Update*****
Tons and tons of junk were caked onto the front of the radiator, behind the AC condensor. So much that it had bent the fins flat, and very little air would pass through.
It wasn't leaking, but being 7 years old, I'm replacing it and should be fine, efter.

Thanks for the help guys.

99 vett babycar