K10 Running hot

[killer_mike]

Hey, have some temp issues with my truck. It has a new thermostat and a rad cap rated 13psi. The truck heats up really quick say 3 to 4 minutes running at iddle, the temp gauge returns to dead cold when the truck hasnt been started.
Read some of the old posts, im trying to find a way to determine the exact culprit, the other day i figured i could run it at night and made a trip of about 269 miles [i had to, is my only truck] the truck was mighty fine, the neddle on the gauge was a little less than 3/4 of the entire gauge reading. But when i got it out the shop, the thing was stupid hot. Im thinking about buying one of those caps with a thermometer, to determine the exact temp reading.

And then maybe replace the pump [got it from a junkyard] and take the rad to a shop; i will check the water pump to make sure is not a reverse rotation pump, i dont even remenber what vehicle or year i got it from.

Thanks in advance.

[Shyguy]

Does it have a fan with a clutch? These will go bad and cause a truck to get hot when it is not move down the road at a pretty good speed.

Checking the gage is a real good idea.

Danny

[70rs/ss]

First, I'd verify the actual temp, as the old guage probably isn't accurate. If it is hot, then new pump (old pumps really aren't worth the risk a new not rebuilt pump is only about $30). What temp is the thermostat? A 210 thermostat will make the motor water heat to 210 before opening and recirculating, so a 180 or 190 is more appropriate for our vintage truck. Lastly the rad, once it is warm, touch the core and see if you have any cold spots, if so, some tubes are plugged. A rad shop can rod out the core but a new 4-row can be had for about $200 Radiators.com I think or ebay, either place is a great source for inexpensive 4-rows) and you'll never run hot again with a 4-row.

[Longhorn Man]

start off with verifying the guage. Don't bother with the guage in cap junk, you want to know what the ENGINE temperature is... not the rad temp.
Does the truck barf the coolant out when it gets hot?
Does it smell like a hot engine?
Does it crank slow when you shut it off hot and try to restart?
Are you getting spark knock when you hit the throttle when the truck is hot?

[mahanian]

A quick way to check and make sure the thermostat is opening and the water pump is building pressure is by checking the upper radiator hose. Start the truck and put your hand on the upper radiator hose. When the engine is cool you will be able to squeeze the hose together. When the truck reaches operating temps the thermostat will start to open and you will literally feel the hose heat up starting at the thermostat housing and working it's way to the radiator. It will also be very difficult to squeeze the radiator hose together.

[Longhorn Man]

but that won't tell you what temperature the t-stat is opening at.

[69TowRig]

I had a similar problem, turned out the old radiator had too many clogged tubes. Good excuse to pitch the 2-row and go to a 4-row in my case...

[mahanian]

Originally Posted by Longhorn Man

but that won't tell you what temperature the t-stat is opening at.

You're right, but I thought he already knew what temp it opened at. T-stats either open or they don't, there is no variation in what temperature they open at

[killer_mike]

No clutch fan, is a direct fan. I bought a new pump today, an Airtech from Advance Auto and going to check the thermostat or just might ask the guy what did he put in it [180,190...] even bought a new lower rad hose, needed one anyways, i was using the short style rad hose. I dont know what type of rad i have 2 or 4 core, never had to deal with overheating issues before till now.
My best guess is the water pump, because like i said, i pulled it out of the junkyard, i just wanted the PS convertion to work, so who knows for how long that thing was in whatever truck. I let u know my findings.

Oh and yes it does gush out coolant, and gives me a hard time to start again after is hot.

[killer_mike]

Got the radiator tested and it flows 41 gallons per minute, according to the guy thats very good. Put the new pump, and waiting for the RTV to cure. Called the shop and asked the guy what thermostat he put in and he said is a 195 ['maybe' on his own owrds]. But im going to check it, make sure is not backwards or something, they might do it on purpose to keep sucking money out of me.
Im trying to find a lower rad hose, and i did but the one i found is not wide enough to fit the rad, i think is a 2" diameter. This morning i restricted the heater core intake hose and squeezed the upper rad hose, didnt feel the surge when i let go, i did it when it was cold and when it was hot that i could barely hold it for more than 2 seconds. The rad shop said the last thing would be to check the head gaskets, but i changed the oil on friday and didnt see any strange colors in the oil or anything other than oil.

Any sugestions?

[69TowRig]

Should use a 195 normally on that thing. I accidentally put a 180 in mine and it always runs cold, even on the highway on hot days.

Let us know how it goes after the RTV cures...

[steelhorse]

You mentioned a ps conversion,did it overheat before you did this?If you switched to a later style serpetine belt system you may need the water pump that works with it.

[killer_mike]

Frustrating, checked the thermostat, 195; put a coolant reservoir, put a 50/50 misture in the rad, checked the timing, was filling the rad while the truck was running and checked belt tension and hose clamps it went up to 210 and started splurting coolant to the reservoir while it was running.

I dont know what else to do, i ran out of ideas.
The other engine had the same PS conversion parts that this one has on it and it wasnt overheating like that even though the other engine needed a serious valve job and gaskets replacement and many other things. The last thing would be headgaskets but is a brand new engine.

Anyone with any ideas or experiences of odd overheating causes?

P.S. Used an external thermometer to check the temp on the engine.

[mahanian]

Did you have radiator cap off when it started splurting? If so, you can't really judge it by that because the cooling system doesn't work properly with the cap off. Also, every 1 psi of system pressure raises the boiling point 3 degrees so without the cap on your boiling point goes way down.

This might be a dumb question but are you spinning the water pump the right way? It's not a reversed serpentine pump or something like that?

Maybe you have a blockage in the block or heads. You can do a pressure flush, prestone sells a kit that uses your garden hose as the pressure.

You might have a trapped air pocket as well. You can burp the cooling system by putting the front wheels on ramps or something and run it for a few minutes without the radiator cap on, but don't let it boil. Just another possibility...

[killer_mike]

I was wondering about that and asked the clerk at advance auto about the pump rotation and they said is not a reverse pump, it should rotate the same direction of the crankshaft wich is clockwise.
I will look for white smoke, check the dip stick, oil in coolant; coolant in oil.
But i see those bubles coming out when the caps is off and the up and down motion of the coolant level in the rad.
If theres no improvement, will have to take it in, dont know how to perform a leakdown test or compression test and dont have the equipment for it.

Hopefully is something simple, not the head gasket. And is there any chance that no fan shroud cause overheating on these trucks?

Originally Posted by mahanian

Did you have radiator cap off when it started splurting? If so, you can't really judge it by that because the cooling system doesn't work properly with the cap off. Also, every 1 psi of system pressure raises the boiling point 3 degrees so without the cap on your boiling point goes way down.

This might be a dumb question but are you spinning the water pump the right way? It's not a reversed serpentine pump or something like that?

Maybe you have a blockage in the block or heads. You can do a pressure flush, prestone sells a kit that uses your garden hose as the pressure.

You might have a trapped air pocket as well. You can burp the cooling system by putting the front wheels on ramps or something and run it for a few minutes without the radiator cap on, but don't let it boil. Just another possibility...

[Shyguy]

Just shooting in the dark here, but were the heads or intake off recently.

Seems like in my distant memories I recall that if the head gaskets are instill backwards they could cause a coolant flow problem and maybe the intake gasket.

Just guessing actually.

Danny

[ed2552]

A fan shroud helps, but shouldn't make it run that hot, there is a deeper problem, more than just a fan shroud.

[killer_mike]

I never touched the heads on that engine, heads came assembled from the factory, the intake gaskets i put them myself so theres a chance i put them wrong or something but i cant recall doing that.
Just for kicks let me post whats on the engine:

-SBC 350/290
-Edelbrock Thunder AVS
-Edelbrock EPS Performer Intake
-Dynomax Blackjack headers for SBC 305-400
-MSD Blaster 2 coil and MSD HEI Dist ready to run

[killer_mike]

In the process of cheking the intake gaskets, just need to get some compressed air to blow away the debris from grinding the firewall so i can take the dist out.
And found some leaks on the rad wich i thought where the hoses, but have to replace the hoses anyways.

[killer_mike]

Intake is out, no coolant on valves or under the intake or push rod area, just a little bit of uncontaminated oil. But the gaskets on the intake the same area on both gaskets is burned and that is on the middle hole between the chambers wich i think is for vacuum or something, the 2 rear ones have coolant inside, but the ones on the front smell like coolant was there, but the thing is that my intake dont have holes there.
Now im wondering if i was supposed to do some machine work to open those holes because this leads me to think that the cylinders 1-3 and 2-4 are overheating.
I tried to get a cooling system diagram for the block or something that tells me where the coolant should flow through on a 350, but no luck.

[LONGHAIR]

Originally Posted by killer_mike

But the gaskets on the intake the same area on both gaskets is burned and that is on the middle hole between the chambers wich i think is for vacuum or something, the 2 rear ones have coolant inside, but the ones on the front smell like coolant was there, but the thing is that my intake dont have holes there.

That burned area in the center of the gaskets is the exhaust heat cross-over. It is designed to speed-up the warm-up of the engine and to provide heat for the old style divorced choke coil. Most guys block them off. The only negative side of that is slower warming in cold weather.

The overheating could be coming from several sources.
I would try to confirm coolant flow first. Just because the radiator is flowing when tested, does not mean that the coolant is flowing in the engine itself. Someone suggested flushing....That is probably a good idea. Anything that could be in the coolant passages in the block may be causing a blockage/restriction.
You should definitely check the thermostat. Make sure that nothing is clogging that area. Pieces of gaskets or sealant, etc.

Water pumps are fairly simple, there really isn't anything that can really go wrong there....as long as it is turning the right direction. Back in the olden days we didn't have that worry.

It is "theoretically" possible that there was an air pocket stopping the flow, but that usually goes away the first time the thermostat opens. If you are puking out the radiator over-flow the 'stat is definitely opening.

Yes, lack of a fan shroud can make you run hot, but you are probably in a borderline situation anyway, if it does. Since you said that it gets hot so fast, that is probably not the problem in this case....but I would still get one.

What kind of fan is on this thing? You stated that it was not a clutch fan correct?

[killer_mike]

The fan is conected straight to the water pump. Im gonna check my carb too, im suspecting it might be too rich, didnt tune it when i put it on, neither did the mecanic shop when it didnt start.
Is there something that chavy engines come from the factory that is to be taken off before installation like some coolant passages plugs or paper somewhere...?

[killer_mike]

Ok, its been a while and alot of fun things happened to the truck.
The overheating, well, we tried taking the thermo off, and it does run good, except when its on idle, not going anywhere, the temp rises, i bought a brand new shroud, because the fan is about 8" away from the radiator, so theres barely any air going through the radiator, except of course when its moving.

When the truck is moving the temp is around the 160s, not bad , had the rad tested and everything is it checks out better than new, i dont know how it happened, but that was what the rad shop told me, the average for my 4 core was i think somewhere around 45 gallons per minute and it gave him almost 50.

Alright just an update and someone might benefit from the tips and my mistakes.

[Longhorn Man]

so you are rolling with no thermostat now?

[haysonj]

I didn't read this entire thread but I did have a factory engine blow a head gasket within the first 20 or 30 min. of starting. It blew between the cylinder and water jacket so the heat from the compression was going into the coolant. If you take the cap of the radiator you will see air bubbles in the coolant. I would do a compression check on the engine to see if all cylinders are equal. If not you either need to get a leak down test or just pull the heads and replace the gasket. Should only be one side.