Cooling system problems

[Beanzy]

Hello everyone, I need some help with a problem I am having with my cooling system in my 1997 Bonneville SE w/a 3.8L non supercharged engine. The car sat for about 8 months because it took me that long to find somewhere to buy a set of pre-bent stainless steel brake lines, anyway, after installing the brake lines the car ran fine for about 2 months and then the problems began. First I had to replace the battery. Then the alternator quit. And now the cooling system trouble. 1st the temp gauge began fluctuating, high (220 deg.) and then back to about 180. Somehow that problem seemed to correct itself but started again in about 1 month. I have none of the tell tale signs of gasket problems, no water in oil, no oil in water, no visible leaks, and the car runs great but 2 times it built up pressure in the radiator bad enough to blow coolant out of the upper rad hose. I replaced the tstat and the cap, my temp holds steady at 195, no white smoke from the exhaust. Then the 2nd high pressure problem. Does anyone think if I replace the water pump, radiator, put aluminum hoses in the tensioner, and new upper and lower rad hoses this may solve this problem. Also, my cooling fans are working and I never had my temp over 220 deg, so I never overheated the engine. Thanks in advance for any help, Bill

[CMNTMXR57]

Probably just a flaky ECT sending unit or the stepper motor in the gauge if the car isn't actually physically overheating. 195* is right where it should be with a stock t-stat.

My inclination is the ECT sending unit being the culprit.

[96 SSEi]

hi, if the upper rad hose was original, it will swell with age and the spring clamp may cut into the hose - happened to my 2000.

yes, you cant really trust the gauge as above - if you get a scantool and pull the engine control/coolant temp, it pulls the reading from the PCM and will be accurate.

first rule out the funky gauge, then you can diagnose with confidence instead of blind assumptions.