Topic: Heating problem
in Forum: C3 Cooling and Heating Systems
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Ok on my conv when I go highway speed the temp gage will show 200 but when I come to a stop it drops to 180. Could this be a fan clutch problem.
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Frederick, MD - USA
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Vette(s): 1969 convertible L71 427/435 4-speed black interior
It could be one of several things, but my first inclination is to look at the lower radiator hose. If the internal spring is missing or rusted away, the hose can collapse under vacuum pressure, thus creating a restriction. When you slow or stop the hose goes back to normal shape and allows coolant to flow normally.
To check the fan clutch, have the car idling at normal operating temperature and shut the engine off. If the fan clutch is OK, it should stop rotating almost immediately with the engine. If it keeps spinning for several rotations it's bad. Usually with a bad fan clutch you'll find overheating at idle when it should be locking up with engine rpm...just the opposite of what you're experiencing. At speed the fan clutch should be free wheeling anyway.
Other things to check...tightness of belts, seals properly installed around the radiator and air deflector in place under the front end.
Start with the easiest and most basic...belts then work up to more complex. You should be able to squeeze the lower hose and feel whether the spring is present. Visual check of the fan clutch and whether seals are present. It could be as simple as slipping belts.
Replace the thermostat. and run a flush thru the radiator. I would bet it's stuck open and the radiator is a little clogeed..mine did the same thing too.
yostusota 2010-12-31 09:47:42
Rich
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..and, of course, if it's an older motor, the temp. will increase as the load increases until it's over 200, and can run that way all day without harm. Just makes you feel a little uncomfortable.
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The fan clutch really shouldn't be doing anything(much) while driving except just going along for the ride. At speed, there should be enough air flowing thru the rad to keep the temps in check. Bruce is prolly in the right area when mentioning the lower raditator hose. I don't know about being able to squeeze it tho, unless yours is easier to get to than mine!
I'd have to go with a restriction in the system, most likely a hose, but possibly the thermostat....might even be a smidge low on coolant.
I'd have to go with a restriction in the system, most likely a hose, but possibly the thermostat....might even be a smidge low on coolant.
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That's funny..I could grab the lower hose on mine..just haven't..that spring thing inside the hose is that a stock thing..mine was a completely open thermostat and a clogged radiator..temp went up while driving and back down once at idle..unless I sat for to long then the temp would go up yet very slowly..I didn't even think that I had a thermostat untill I removed it..
Rich
Rich
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Frederick, MD - USA
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Vette(s): 1969 convertible L71 427/435 4-speed black interior
The spring inside the lower hose is stock, unless you have a replacement that's a flex hose. There are some new replacement hoses that don't come with springs anymore...either they're stiff enough or have a spring wound inside the rubber...don't know which. That might be fine for a new hose, but what happens when the hose material softens with age? Maybe I'm old school, but I find the presence of an internal spring comforting.
The problem could be a combination of several things due to age...hose, coolant level, sending unit or gauge, belts, radiator seals, radiator fins or tubes clogged...any combination could be playing a minor part but together could make it happen to the degree you're noticing.
Ok so the lower hose should have some sort of spring in it..ok..makes sense how that would make for some real wierd cooling problems..it isn't all that hard to check on these cars either..probably the easiest thing next to fluid level..I will put that in the data bank..
Rich
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Vette(s): 1979, Targa Blue (72 Color), Pace Car rear spoiler, L88 hood, Dark blue factory interior, 525HP 406, HD 700R4, 370 gears,Steeroids, composite rear spring, TT IIs wrapped in T/A Radials.
Same darn thing was happening to my car after I swapped in the 406. The lower rad hose with the spring was the fix!! Get ready for the price!! I think I paid a little over $40 for one. All the parts counter hoses had no spring...had to get it from a Vette parts place.
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in Forum: C3 Cooling and Heating Systems
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