vannatta20

iTrader: (4)

I have a 2000 5.3 installed in a 68 C10. I used a 2004 truck surge tank with a used LS1 radiator and fans. I keep over heating but it does so very slowly. Seems to be fine driving around town. When I drive on the highway for 25 or more minutes it will then slowly over heat to 250F. If i pull over and have the fans on high it still doesnt want to cool. The upper hose is rock hard. The spots where the fans are pulling air against the radiator are somewhat cool. If I rev it up to 3000 rpm it will begin to cool down. Why would it do that? I checked the thermostat and it opens like it should. The system seems bled but maybe I did it wrong? Def seems like a flow problem. I ran the truck with the rad cap off to see flow. It did get some bubbles until the t-stat opened up then it erupted! shot coolant everywhere.
The water pump is not leaking and the truck does not use any coolant. Please help this truck is my daily driver!

vannatta20

iTrader: (4)

vannatta20

iTrader: (4)

sb50

iTrader: (1)

I'm no expert but I work as mechanic (or fake as a mechanic lol) and to me those are the signs of a blown headgasket. People always associate blown headgaskets with smoke and oil and antifreeze mixing with oil which is not always the case. The reason the upper radiator hose is hard is due to pressure being forced into the coolan.The other sign to me is the coolant erupting. I am human and I am wrong sometimes. The make a tester to check for this.No I cant explain why it cools down when you rev it to 3000 rpm. This is only my opinion and I am by no means diagnosing your vehicle this is just my .02

sb50

iTrader: (1)

Also how are your vent tubes on your heads ran?. Could be an air pocket

vannatta20

iTrader: (4)

I ran the vent tube to the top of my water pump. Drilled a hole in the pump and installed a fitting.

RPD_Vette84

iTrader: (30)

id say for testing before you pull heads, try removing/changing the thermostat.

chiaj144

iTrader: (4)

Is the pump spinning the right direction? Remove the thermostat and try it again just to see if anything changes.

vannatta20

iTrader: (4)

I assume it the WP is spinning the correct direction. It spins counter clockwise. Thermostat is good as well.. Im thinking the WP could be bad and is not flowing coolant. How to I check for a plugged radiator?

ls1nova71

iTrader: (4)

Is this a new problem? Or a new swap? How long have you been driving it? Are you sure its full of coolant? I know you say you have the surge tank... but I would pull the upper hose and fill it until full. Did you look in the radiator through the cap opening a?nd is it mucked up

vannatta20

iTrader: (4)

It's done it since the swap. Changed the caps. I am going to fill through the hose and see if my friend has an extra truck water pump and try that as well

ls1nova71

iTrader: (4)

How long has it been done?

I have also seen thermostats do what you described too, be cheaper and easier to try first.

vannatta20

iTrader: (4)

I tested the stock one against a new one and they both worked like they should. My top hose is lower than the top of the radiator. When I remove to fill I lose a bunch of coolant. I'm using a f body radiator.

RPD_Vette84

iTrader: (30)

i still say try the thermostat if not pull the waterpump off and see if one of the passages is blocked. my 91z never had the heads off and yet the headgasket was on the wrong way causing it to heat up. i looked it up and apparently it was a common prolem.

also the car should go into safe mode if it was gettin that hot. which seems like it might be another problem.

heres a pic of the headgasket blockin the coolant passage.

vannatta20

iTrader: (4)

I heard lots of gargling after i turned off the engine today. air?

Steve68

iTrader: (23)

I'd say yes, sounds like you have a large air pocket, some how you have to fill the block and then the radiator, keeping the upper line loose to let air escape, when you start it up and it starts coming up to temp,

forcd ind

iTrader: (7)

i always fill the LS engines thru the top hose-the thermostat is on the return, and wont open w/o water behind it, so its just easier to fill the top hose-still you may get a little air, so i pop the hose off the air bleed to

the_merv

iTrader: (88)

Make sure your mix is 50/50 or close to that first.

Start without Radiator Cap on, wait for the stat to open and fill to normal.

I wouldn't have used that Truck Tank..just a normal overflow would've worked. That and the hose is on the wrong spot, should be on the upper one. Cap the lower one.

vannatta20

iTrader: (4)

I pulled the upper hose today to see if it needed coolant. It did. I emptied an entire gallon... Test drove it in 100 degree heat and it stayed around 220-230ish. seemed a bit warm still. It did not over heat though.

Steve68

iTrader: (23)

Souldn't normal operation temps be 185-210 ??

what kind of guage do you have??

with adding a gallon, looks like it was low, with a large air pocket, still might be some air in there too,