Overheating 4.7. seeking advise. troubleshooting started

[RobA]

Son told me his 2003 1500 with the 4.7 had a check gauge light come on and low voltage showing on a gauge. After popping the hood the coolant reservoir cap was blown off and coolant had soaked the serpentine belt. After refilling the coolant we ran it in drive way with a scan tool to watch the ECT. It was idling in drive way at 210° so we opted to replace the thermostat thinking it may have failed. after replacing the thermostat and running a garden hose through the radiator, we bled the coolant system. We ran it on the interstate and the ECTS got into the 220s and blew the cap off again. After a long delayed drive home and some additional water and coolant. When home We tested for exhaust gas in the cooling system using the blue fluid (combustion leak detector) after 5 minutes of idling in driveway while testing the fluid was perfectly blue still. No hint of green or yellow. Just to try it, we sucked a bit of exhaust from the tailpipe into the tester and immediately had yellow fluid in it..
Tester was inserted into the reservoir as radiator does not have a cap. We are thinking radiator is failing or water pump is failing. Through-out all tests the heater blew hot air and even blew hot after loosing some coolant. Ambient temps where in the mid to high thirties while overheating. Radiator flowed a garden hose well. No signs of backing up with average water pressure through a garden hose.

 

[RobA]

Seeking any advice or direction to try to eliminate water pump or radiator from list of suspected parts or possibly things we have not thought of.

 

[Ken226]

Those are pretty low temps for there to be enough pressure to blow the reservoir cap off.

Have you checked the cap itself for any damage?


A Google search shows that a 2003 4.7 uses this setup:




That reservoir pretty much uses a normal 16psi radiator cap. About the only way I could see that cap being blown off by such a small amount of pressure is if the plastic around the filler neck were pretty badly damaged.


The cap needs to seal correctly and hold pressure to prevent your coolant from boiling at too low of a temp.

The temp at which coolant boils is dependant on the pressure, and the caps job is to maintain pressure.

 

[RobA]

Cap appears in good condition at a glance, the plastic on the reservoir itself appears to have been chewed up a little bit how ever it still has a substantial amount of plastic that that cap locks on too. I don't have tools to pressure check the cap and I believe the cap is rated for 15psi before venting. How ever it has now been found laying on the reservoir twice.

 

[RobA]

 

[RobA]

I think your right about the cap blowing off too easily. But a nearly 230 degree temperature reading on a unloaded truck at highway speed seems a bit high to me. Do you agree? Also the temp gauge has never gone above center position before the cap started blowing off

 

[Ken226]

I think your right about the cap blowing off too easily. But a nearly 230 degree temperature reading on a unloaded truck at highway speed seems a bit high to me. Do you agree? Also the temp gauge has never gone above center position before the cap started blowing off

Yea, while the cap shouldn't be blowing off at 230, it's higher than I would tolerate.

I use a 192° CalorStat thermostat from RockAuto in my truck. It's been working great, so far.

That filler neck looks pretty chewed up. That tank is a pretty cheap part to replace. This may be a good opportunity to flush and clean the coolant system with some CLR or RMI25, then do a refill while also replacing that reservoir tank and new cap.

22 years is a pretty good run for the original. The truck has earned itself some new replacement parts.

 

[RobA]

I absolutely agree the truck deserves some parts.
All our kids pay for their own vehicles as as we feel it's a good learning opportunity and a lesson in responsibility. My son who's having the issues is a high school student who wrestles and works a part-time job.

The main goal of seeking advise on here is to limit the price we are spending on replacement parts and get the problem solved with out having the head issues that are more or less common on these trucks from overheating( based on information on the Internet as this is first 4.7 I've personally dealt with.)


I appreciate your advice and think a new radiator, reservoir and cap is going to be the direction we head in. I'll report back after ordering and installing said parts with sons help.

 

[jws123]

Besides a new radiator have you checked your clutch fan? they do fail with age and will make the truck overheat at idle/overall run hot make sure to burp the system by removing the bleeder screw. Its right where the upper rad hose goes to engine After that you will want to burp it the normal way aswell

 

[Stoffregen Motors]

When filling the cooling system, you will need to burp the air out of the system before putting the radiator cap on. Did you do any of that? Do you know how?

The easiest way to burp the system is to park the truck on a slight grade pointed up hill. Then, with the heater on (not the blower) and the rad cap off, let the engine run until it comes up to temp and the t-stat cycles at least once. That's the easy way.

The other way is basically the same but uses a funnel attached to the radiator cap like this - https://www.amazon.com/OEMTOOLS-870...ling/dp/B01A2CQSU6/ref=asc_df_B01A2CQSU6?th=1
Then do the same, let it run until it comes up to temp and sucks all the coolant into the motor. Replace the cap before the engine cools, because as it cools it will tend to push coolant back into the funnel. Then top off your coolant recovery tank and run it again.

 

[RobA]

Thanks guys, new radiator installed and new reservoir bleeding now and watching temps

 

[RobA]

Engine coolant Temps hit nearly 220 in the drive way during bleeding procedure and the lower rad hose didn't heat up. The side left side of the radiator stayed cold, not much if any above the ambient temp of mid 40s, heater core would remove enough heat when the blower was on high to keep truck around 200° but when blower was on lowest setting temps would rise again. after about ten minutes of this I shut it down to cool.

The new thermostat was functioning before install (I tested in boiling water).


Seems like the coolant is failing to cycle to me. Any idea on next steps other than removing and inspecting water pump. There is a steady stream of coolant pumping into the reservoir from the top of the radiator and the coolant flow keeps up with the heater. Could this still possibly be a water pump failure? Do you think a drive without the thermostat would show if coolant flow was sufficient?

 

[RobA]

Should I turn back to the idea of the head gasket? Possibly a leak down test? Is there a possibility that exhaust gases never made it into the coolant reservoir do to lack of circulating coolant? Would the added exhaust gasses from a failed headgasket impede coolant circulation?

 

[Stoffregen Motors]

Sounds like your radiator might be blocked. But you said you just replaced it. There's obviously a flow issue going on here.

the lower rad hose didn't heat up. The side left side of the radiator stayed cold,

 

[Stoffregen Motors]

Have you tried a mechanical temp gauge? Electrical gauges are prone to faulty readings for simple reasons. Bad ground, bad contact, bad sending unit, mouse eaten wires, etc.

Get a meat thermometer and poke it into the top of the radiator while it is running and see if the temp corresponds with the temp on the dash gauge.

 

[RobA]

I'll try a mechanical thermometer and yes really seems to be a flow issue. New radiator, new thermostat(checked in boiling water) strange thing is that the heater core seems to have ample flow and the reservoir is fed off the top of the radiator and flows well too. So I'm hesitant to replace the water pump as Its not leaking and appears to be working

 

[jws123]

I'll try a mechanical thermometer and yes really seems to be a flow issue. New radiator, new thermostat(checked in boiling water) strange thing is that the heater core seems to have ample flow and the reservoir is fed off the top of the radiator and flows well too. So I'm hesitant to replace the water pump as Its not leaking and appears to be working

I just want to make sure here your not running striaght water correct? 50/50 coolant? cant run straight water it boils to easy have seen people try to do that on modern cars.

 

[RobA]

Running Brand new 50/50 mix.

Question:
Generally the spring side of a thermostat goes to the block on most most vehicles but considering the thermostat is under the block instead of on top does that mean the thermostat goes in with the spring side away from the block ?

 

[jws123]

Running Brand new 50/50 mix.

Question:
Generally the spring side of a thermostat goes to the block on most most vehicles but considering the thermostat is under the block instead of on top does that mean the thermostat goes in with the spring side away from the block ?

tstat spring side goes into the block

 

[Marshall]

if half the rad and lower hose is cold and motor is hot, then you have no water movement.
New rad, so that should be OK.
Quick test , take thermostat back out and run motor, does anything change?
if so , get a better thermostat.

Otherwise sounds like the water pump is shot.
I have not worked on a 4.7
Put new rad hoses on, you could have a collapsed one.