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frscke1, pjfroncz, Wedgy
Total Likes: 6
Original Post (Thread Starter)
1993 G20 4.3 V6 heat not working #798934 11/25/2022 6:00 PM
by pjfroncz
Well... I flushed the cooling system and replaced a bunch of parts since there were some swollen hoses and could smell antifreeze when the heat was on. And by the looks of them, all parts were original (old). Now the heat doesn't get hot... I had it on for close to 30 min (in park) and it felt slightly warm at times but never hot, and when I shut it off it was blowing room temp.

Here is what I replaced: all heater and radiator hoses, heater valve, thermostat (195 F), thermostat housing, water pump, fan clutch, and heater core (...not fun).

The one part I questioned was the fan clutch. I replaced it with a severe duty, but what was in there must've been a standard or heavy duty by the look of it. Could this be the culprit? Or what else am I overlooking? Is it possible I didn't reconnect something properly behind the dash when exchanging the heater core? AC is working and it properly switches from vent to defrost etc.
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Re: 1993 G20 4.3 V6 heat not working #798973 Nov 26th a 08:59 PM
by CatFish
My GM vans (94 & 95) have always been very slow to warm up. Started cold and left to idle they can take 20 to 30 min for the gauge to read at normal. Driving they will usually warm up much quicker, in about 4 to 5 miles. I use a 195 degree stat in both my current vans.
The later GM generations don't block the coolant flow entirely when cold, they allow some circulation between the rear of the intake manifold and the rest of the system.
The V8 and V6 engine designs we have in our late 80's to mid 90's Chevys were around 30+ years old when ECM controlled fuel injection came about. The EPA required the ECM to limit emissions during cold start conditions. The 30+ year old design was compromised in various ways to satisfy those smog rules......They found they could control the fuel mixture better if the system warmed up slower and all together. So they designed the system to warm-up slower and programmed the fuel ratio accordingly....
You've may have noticed before on older vehicles the temp gauge would start to rise during engine warm-up and then take a sharp drop as the thermostat opened and cold coolant from the radiator entered the engine. Our older ECM systems don't like that......

3 members like this
Re: 1993 G20 4.3 V6 heat not working #799052 Nov 28th a 06:33 PM
by Wedgy
Originally Posted by pjfroncz
I've concluded the problem was impatience plus a healthy dose of naivety. Ran it again for about 40 minutes in park including burping it real well and the heat now works so I guess it was an air pocket. I'm still concerned about the severe duty fan clutch and if it is too much... The upper radiator hose never got warm and the temp gauge never got above 120 or so. Any opinions on this are much appreciated.

I'd not be too concerned, motors hafta work to produce heat. Be glad you got it sorted. IMO experience, you can never have too much radiator, and too much is way better than not enough. Same with coolers and auxiliary fans. I run both on the 1 tons.

The B250 5.2/318 is the most cold blooded smallblock I have ever owned. New radiator, fan clutch, didn't have a Tstat in it, now has a 195. Fine, stock.
I do see custom aluminum radiators for the Dodges now. I would/should consider it for the B350. And the 1990 G30 7.4 BBC EXT, although it runs cool, oil, trans coolers, aux fan.

Smallbock Chevy trucks seem to have enough radiator, compared to the Mopar's, IMO. For sure, the up to 2003 5.2, 5.9 Durangos, My 2000 5.2 Durango ran like a scalded dog, but would get hot even looking at a desert hill with the boat in tow. With a trans cooler, fan, nothing helped. Full passenger load, boat in tow pulling the long hill out of Willow Beach it was it sketchy hot, wouldn't cool down pulled over. We finally got to a downhill up on the highway back to Kingman, the temp came down. My 97 GMC 1500 would pull in the desert noo problem...

My B350 5.9 fan/clutch in the Xplorer howls like a banshee even in the cold, snowing in Flagstaff. It's ridiculous.
In slow off road maneuvering in Yucca Valley searching for an address in 100 degrees heat, or pulling the boat up the grade from Bullhead City to Kingman, even with coolers and a junkyard rice burner electric radiator fan, it still needs to pull over and cool off.

Why frscke1 runs the biggest custom aluminum radiators he can get in both of his BBC G30 7.4 EXT vans.

Stay cool! Good Wrenching
1 member likes this
Re: 1993 G20 4.3 V6 heat not working #799175 Dec 2nd a 02:36 AM
by soundhd
Gotta drive it for it to get even warm. Same issue with my 91 (5.0) Shorty….Replaced pretty much everything and first start up idled for about 45 minutes and hardly any heat at all so took it out for it’s first “cruise” and after about 30 minutes or so the heat started to work better…..have to work em’….
1 member likes this
Re: 1993 G20 4.3 V6 heat not working #799025 Nov 28th a 12:48 PM
by Astrocreep66
CatFish is a veritable wealth of knowledge on many subjects. He is the MAN!
1 member likes this

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