Riddle me this . . .

[prophiseer]

Alright, seeing as how this has got me completely stumped right now . . .

99 GAGT 3400 . . .

Coolant temp per the cluster gauge stays around 195F, nothing warmer than 200F - heat from the vent is . . . warm, not hot like it should be (sorry, I haven't stuck a thermometer in the vent yet); but it's not 'burning hot'

Anyways, on to the weird stuff . . . coolant level is perfect, hasn't budged at all; the motor warms up properly, 10min after a cold start from 30F the gauge is 1/4 up, and scan tool confirms that reading is correct - so I've eliminated the thermostat being stuck open, and considering the temp doesn't come over 200F I say the thermostat isn't stuck closed; I have coolant flow, viewable in the reservoir tank when the motor is revved up; no visible coolant leaks at all, coolant pressure cap is new, coolant fans function properly and are off as they should be; . . . no coolant in the oil, nothing else unusual; I highly doubt the heater core or radiator are blocked, I change the coolant every 30k . . .

So, I can't figure why the temp won't rise above 200F, and why I'm not getting 'hot-hot' from the vents . . .

any ideas?

[RednBlack]

Leave the engine alone, and look into a heater door not opening, or closing properly. Check flow through the heater core.

[sil]

ya it must be the flow across the heater core
does your car have a/c ?

i had to pull my heatercore and the a/c and clean it real good cuase it was plugged
it also had a foam filter thing that was pretty dirty too

[IsaacHayes]

Dex-cool clogging up the heater core is my guess. 2 Of my friends recently had this problem. One was able to get a flush and it cured up, the other it only slightly helped.

[prophiseer]

well, the blend doors (and control) are fine; no issue there; I spent a while driving it lat night (it stay warm enough in the cab to manage the cold out); and it'll get hot, and then cool down, and on and on; While driving, temp stays right about 190F; Seeing as how the hot/warm seems to coincide with the rise and fall of the coolant temp, I'm starting to lean towards a thermo partially stuck open. Odd, though; they usually don't stick part way

Dex-cool clogging up the heater core is my guess. 2 Of my friends recently had this problem. One was able to get a flush and it cured up, the other it only slightly helped.

Yeah, I know of these problems, clogs the rad, too - reason I dismissed this is simply the fact that I change the colant every 30k, using only Dex and distilled H20, and I don't have any of that "brown death" on anything yet, not even a slight film of the stuff.

[Azrael]

I find that my heat isn't that hot whenever I'm cruising on the highway, even with cardboard over most of the radiator. When I accelerate I do feel the air get hotter, so it's probably the engine itself losing too much heat in the winter. It probably didn't help that I removed the insulation on the inside of the hood.

[prophiseer]

. . . no comment on that one . . .



anyhow, replaced the thermo the other week (it was old anyhow), no fix for this odd issue. I let the car run for 1.5hrs the other day, 80F outside, in the sun, hood closed, heater off . . . temp gauge never once rose above 200, never once heard the cooling fans kick on

how in the hell can a system become THIS efficient? This is making no sense!!