cooling system woes

[Boog]

Hi guys. My truck: 85 k5 blazer, 305 auto, all stock, 138,000 miles.I have a new 195 thermostat, new gauge, new sending unit but it still shows to be warmer than normal. On cold start up, it warms up nicely but keeps going to sometimes 250 before it eases back to a usual running temp of about 220 to 230. Atleast that's what it is showing. It never boils, ever. Water pump is doing it's thing just fine. Radiator was recored 3 years ago, now a 3 row. No loss of coolant out the pipes. I've checked the wire from the gauge down to the sending unit for grounds and found none. Most of the trucks I've seen the gauges usually read on the low side. I think the engine is running some warmer than normal but not enough to boil over. I've seen it read 260 breifly before settling back down to the usual 225 or so. I'm puzzled here. Any ideas? Thanks, Boog.

[69Custom]

I am having similar problems right now. I put in a rebuilt engine and replaced everything except the rad. because it was still good. I replaced the fan last night with a 18" flex fan and seems to help a little. The other thing that I am going to do is to flush the system. I do have one problem that you didnt mention. I seam to run low on coolant, I am guessing because it runs on the warm side.

Hope you can figure it out soon.

------------------
New Project

• 72 Blazer 4WD 307/3 spd, PS, PB, Posi (Current Project)
• 83 Chevy SWB Rebuit 350/TH-350 with shift kit, buckets (daily driver)

http://members.xoom.com/luc_nt

[jamie72]

do you guys have air in you system??
i had that happen once on my 88 put in a 180
themostat,let it warm up with the cap off to let out all the air,be careful thou,
hope this helps
jmaie

------------------
jamie72
72 cheyenne
72 blazer
69 swb
parts bought and sold

3# may be gone,but his legend lives forever...

[bigd65]

i had a problem with my cooling system a few months ago but after about a week and about 350-400 bucks i figured it out. i replaced the head gaskets-wasnt it, i bout a 4 core radiator-wasnt it, i replaced the water pump-wasnt it, i put in a 160 thermostat-wasnt it, put in a flex fan-wasnt it and was a big mistake. finally i went down and bought a brand new clutch for the clutch fan and that was the problem. now all these mods i did do sure helped it alot because now my truck runs about 160 or below even this hot TEXAS weather. these trucks cannot have them flex fans they just dont work on these trucks, i dont know why and it doesnt make any senes but its true. good luck

------------------
85 C10 350/700r4
HOLLEY STREET DOMINATOR IANTAKE
EDELBROCK 1406 COMP. SERIES CARB.
HYPERTECH POWER COIL
FACTORY HEADERS
MAGNAFLOW CAT/MUFFLER/3in. EXHAUST
3.42 REAR GEARS
PROTHANE SUSPENSION-TOTAL KIT
and still going
"thats my toy"
Jeff Dodson
Angleton,Tx.

[Boog]

All I know to do next is hook up an aftermarket temp gauge to make sure what my factory gauge is showing is right. It didn't use to do this. The gauge rises much quicker than it use to, to about 250-260, then goes back down to about225-230. Idling at a stop light in gear, it cools down more to about 210. All these numbers are using the factory gauge. As I said before, the gauge, sending unit are both new. I've used a good cooling system flush before on another truck. Does a real good job. So good I had to replace the water pump the next day! Cleaned the seals right out of it. Ha. Would probably eat the freeze plugs out of mine since it's the original engine and all. I'm not through with it. I'll pass it along when I figure it out. I guess I could try another radiator just to be sure mine isn't blocked up. It looks good down through the filler hole. Oh, and the flex fans. I also have tried one on another truck. Ran it about 6 miles and yanked that thing off of there. Why it was noisier than my exhaust.Best ticket for the fan is the factory thermostatic controlled fan clutch or an aftermarket electric one. Thanks all. I'll be back.

------------------
Boog's 69

[White Cloud]

BOOG you could get a hand held thermometer like you use to check AC outlet temp and see if your guage is acurate. WC

[gchemist]

Boog,

Have you checked to see if your thermostat is not upside down? I've done that before and know of other people who have done it too. Just a thought. I have a 4 core radiator too. The first options are always pump, fan clutch and good flush. Next on the list is a new temperature sending unit. Dirt cheap to replace. You lose some coolant but not much. Rust and junk can build up on the temperature fitting causing false readings. Threads could also not be clean and giving a good ground. I have a 305 even with 100 degree days in traffic it never goes above 210. I would recommend a 190 or lower thermostat. Even in the winter they work pretty good. Getting a 305 over 220 degrees is not good.


My $0.02.


------------------
Gerardo
1983 Custom Truck
TX Plates: "BAD BOW"
http://www.geocities.com/abetterchemist/

[crossy]

my 92 does the same thing ???????? the 85 only does it when toting a real load and everything is new on that. Always check a new thermostat by boiling water on the stove in a pot and dip the thermostat in .if you have a cooking thermometer than you can REALLY check it . I have seen plenty of bad new ones. OH ! use pliers when dipping it into the scalding water or it will leave a mark. LOL. DAVE

[Boog]

Well,I think I have narrowed it down to the radiator guys. It was recored 3 years ago with a 3 row. Everything was fine until not long ago. Since the problem began, I've replaced the sending unit, gauge, thermostat-3 times. I pulled the upper hose and found the water pump is doing good job too( All over the place!hehe. Well not everywhere). The only coolant flow to be seen is from the return hose from the heater core to the radiator. So, apparently, the only circulation I'm getting is through the heads to the heater core and back to the radiator. Even though the tube openings look fine on the radiator cap end, there must be a blockage on the other end is all I can figure out. I'll have it replaced in a couple of days and know for sure. Thanks for all the input guys.

------------------
Boog's 69

[Boog]

Well guys, I put a new radiator on and it still does the same thing. I am bummed. Water pump is doing just great by the way it pumps through the heater core and back to the radiator but doesn't seem to be any action much coming through the radiator tubes. The upper hose gets hot like normal but there doesn't seem to be any flow through the tubes. Does the gauge operate on less than 12 volts? Anybody know? I hooked up a new stock gauge under the hood on 12 volts to see what it showed using the factory sending unit but it was totally off. I think it's too much voltage, dunno. Maybe I'm experiencing a blockage in the head or block, not letting the coolant circulate like it should.

------------------
Boog's 69

[crossy]

boog, if that impeller was the reverse rotation type you would still see flow but would not have any real pushing power.sounds like it is time for ,hoses disconnected ,thermostat out ,block flushing ,and see what comes out . if you happen to take the water pump off again then that would be an excellent time to flush the block .
I just sold my 85 so I eliminated that problem but my 92 only does it when it is idleing/towing with the A/C kicking.Got to think that one is fan clutch related.dunno ? DAVE

[Boog]

Thanks, crossy. I've never flushed one out before without the pump on it. Would a garden hose with sprayer put enough force behind it to knock anything loose in the water passages? I drained it yesterday to put the new radiator on and the coolant looked clean as can be. I'm beginning to wonder about that water pump. Seems that I changed it in the last couple of years. If it is of the reversed impeller design, would it possibly act this way? I don't know. On normal driving, flat land, no load it's showing too warm but on a long pull with my small fishing boat it really soars up there. I've got to find it before I do ruin my engine. Original 85 305, never been opened up with 138,000 on it. Starts when you point your finger at it and uses maybe a quart between oil changes. Kinda proud of it. Thanks.

------------------
Boog's 69

[crossy]

here's what I can tell you . #1-yes it would still flow but no where near enough and would aereate the water bad and air bubbles don't cool . #2- My 92 pump 'looks' the same as my 85 but they turn different directions.#3- there are people rebuilding these cheapo replacement units getting paid minumum wage and maybe "piece work" who don't care. #4 -it seems like you have covered all the bases and it is time to take a 'cheap' stab at something.#5 if that doesn't work it is time to think 'outside of the box' and maybe get a mechanical temp. gauge. DAVE

[This message has been edited by crossy (edited 06-05-2001).]

[Boog]

Well Crossy. Last night I plugged off the heater return line to the radiator and watched to see if there was any flow in the radiator. There was movement but lots of bubbles and the water level went up and down a bunch. Looks like the next step is to buy a name brand pump and while the old one if off, maybe run a bit of water through the engine and see how it runs out. I agree with you it sounds like a coolant pumping problem. I'll whip this thing before I sell it! One way or another. Thanks.

------------------
Boog's 69

[Boog]

Well, this weekend I tried a new water pump. It wasn't the problem either. I'm running out of ideas here. I don't think the engine is actually running as hot as it shows. It can't be. New gauge, sending unit already. I will stay after it. Later.

------------------
Boog's 69

[Carl's 68]

If you have alot of bubbles in your radiator you have a cracked head or blown head gasket.
you need to do a preesure check on your system to see if it loses pressure then you will know if it is a head problem.

[This message has been edited by Carl's 68 (edited 06-13-2001).]

[crossy]

he's right BOOG it is time to go to a REAL radiator shop and let them Pressure up your system to see if there is an internal leak. Exhaust gas will heat up that fluid real quick. still ahving problems with my 92 after the clutch . I think I am headed in your direction. You could also have someone perform a leakdown test ? DAVE

[Boog]

You're right guys. That would be a good idea. Mine doesn't seem to loose any water so that would lead me to think the cooling system is tight.? thanks,.

------------------
Boog's 69

[Carl's 68]

Did you get it to a radiator shop yet?

[Boog]

Hi Carl. No I haven't had it checked yet. I do monitor it closely though. The temp gauge still reads the same way. The radiator pressures up and there is no loss of coolant. With a 195 thermostat, the gauge should be consistently at or around 200 to 210, wouldn't you think? Although, most of the chevy trucks I've been around most always registered much less than actual temps. I will say since I put the new pump and radiator on it doesn't smell hot like it did before. Thanks for asking Carl.

------------------
Boog's 69