Too much cooling?

[Brook Green]

I bought a 1991 gmc 3x3 crew cab 1ton 6.2 diesel 4x4 a few days ago for 1500 american dollars. 83k on the odometer, but very high hours I suspect. I digress.

After I got the thing home I noticed a glycol smell. Upon further investigation I discovered a light drip coming from the drivers side of the radiator. Stop leak worked for a day or so, but the leak came back.

Here is where I have to admit how ashamed of myself I am for not doing a more thourough investigation before purchasing the vehical. The low purchase price, and the low number of miles on the odometer "slightly" clouded my judgment. (since the purchase date I have replaced the passenger side knuckle [egged out tre hole], drivers spindle [wasted spindle bearing took out the bore], drivers inner and outer axle shaft [damaged from the bearing failure, (I swaped out the entire axle assy because I had it laying around)], the drivers locking hub, the drivers outer wheel bearing cup and bearing, the radiator, and pretty soon I will be replacing the ring and pinion in the rear axle, AND the front drive shaft. OH! and the tranny pan. oh, Im digressing again...

So, back to the topic at hand. I replaced the radiator with one I pulled from and older (early 80's 6.3 crew cab 1 ton 4x4) chevy I had laying around, and while I had the coolant out I went ahead and replaced the thermostat with a replacement I got from the local Car Quest. ($23!!!). Now the thing wont get up to operating temperature unless I am power braking it for a 45 seconds or more. It hovers around 150* or less, according to the stock gage. Sure, I dont trust the gage to read an accurate temp, but I dont see any reason why it would read differnt now than before I swapped the rad and t-stat.

After driving it like this for a few days I swapped out the temp sender in the radiator, but that made no change.

so I have two questions.

1) Did I put the t-stat in backwards, which is causing the coolant to flow too freely through the radiator?

2) What does that temp sender send to?


Sorry for the rambling, and thank you all for such a great forum!

Sincerely,

Brook Green
www.akfabshop.com (http://www.akfabshop.com)

[G. Gearloose]

Hey you the guy who made Project Freak? If so, good show!

I don't think a backwards tstat would do that, I think it would have the opposite effect ; delayed opening.

Factory gauges are not known for accuracy, either.

Perhaps take the tstat out and observe its operation in heated water, with a candy themometer. What brand was it?

Factory plumbing routes continuous water through the heater core, then to the radiator. That means its always pulling cool water from the lower rad hose to replace it, cooling the engine even with the tstat closed.

I had a 4-core on my K20 that cooled extra well, and the engine didn't make much heat, so I routed the heater conventionally, water pump to crossover, plugged the 3/4" rad inlet, and that improved heat retention, winter warmup and idle heater performance.

Could be you finally have a good performing radiator, but the tstat is still suspect for now.

[ 06-21-2005, 02:12 AM: Message edited by: G. Gearloose ]

[mhagie]

83K? maybe 183K, or 283K is probably closer to actual.
Oh well its bad now but when you are finished you will know exactly what you have and by then a good truck.
Merle

[Brook Green]

Ya, thats me.


Its definately not over 100k miles. The windshield, hood, and grill are all OEM pieces, and there isnt a single rock chip in them. This truck was shipped when new across the Inlet to a small village with very few roads. The damage is from being driven down dirt roads for all of its 80,000 miles. :eek:

What supprises me about the "new" radiator is that it came from another very high hour truck. Looking down the filler hole you can see white buildup on the tubes.

[DmaxMaverick]

Brook

That sensor in the radiator is not for tempurature. It is a coolant level sensor. Later models have them in the coolant overflow tank.

If your thermostat is really passing that much coolant to prevent warming up, your fan clutch will also be continually engaged. It is the temp. of the air passing the clutch that causes engagement. Once the engine is up to temp, opening of the thermostat causes the fan clutch to engage, and it should even at 150

[Brook Green]

After long brake stands the under hood temps all seem ok. Using an IR thermometer to check the radiator I see temps around 190*.

The t-stat I installed is a car quest that had an additional extension and spring making the t-stat about an inch longer than the one I pulled out. Im leaving on a 175 mile trip in a few minutes, so I will take the old t-stat and a new gasket with me.

Thanks for the info on the sender, I was wondering why they would want to sense radiator temp. tongue.gif

[NH2112]

If the heater blows good and hot, disregard the gauge :D I've used my multimeter's thermocouple probe to take coolant temp right at the thermostat before, by snaking the probe under the upper rad hose at the gooseneck. Found that my gauge was inaccurate, and that the temp hovered within 5 degrees of rated t-stat opening temp.