indirocz28

iTrader: (7)

Been chasing this issue for quite some time, been through lots of testing and test drives, and lots of coolant.

First, this is a 5.3 swap out of an 03 Tahoe into my Jeep YJ.
The only test I haven't done is an actual block test to see if there are exhaust gasses coming into the coolant system. I plan to try that tomorrow evening.

First off, let me say that this is an off road race Jeep and spends lengthy amounts of time in the 3-4000 rpm range.
It has an AC Delco water pump that has about 300 miles on it now.
The compression tests of the engine show 150/148psi across all 8 cylinders and the coolant pressure test holds 17psi for as long as I care to hold the pump and look at it. Probably about 5 mins or so before I release it.

I have tried testing with the thermostat in and out, and have recently put in a larger radiator as well.
Coolant is fresh and clean dex cool, and engine is clean inside as well.
I've tried several different psi ratings of caps also. On the old radiator I kept having issues with the cap not sealing tight. That has since been rectified, and coolant will now push past the cap into the overflow.

The fan I am using is a Ford Taurus fan on a switch on high at all times.

I can idle around and crawl around off road parks all day long without it getting hot.

The issues arise under load when driving at speed (75mph @35-3700rpm) within only a few miles.
Or if I hold the revs up while sitting in the garage watching temps rise.

If I let out of the gas, and let it sit and idle, the system will cool off on its own.
As long as I'm in the gas, and driving the temps continue to rise.

I had a trans and PS cooler mounted in front of the radiator, I had previously moved it to behind the radiator for testing and it made no difference.

I am using the ICT Billet high mount alternator bracket like found here:
http://www.ictbillet.com/ls-alternator-power-steering-pump-bracket-accessory-kit-truck-lsx.html
And according to the picture the belt is routed correctly, and have verified that the water pump turns in opposition to the crank.

I have also plumbed a rear steam vent into a T, then tied the front steam vent into that and run the hose to the radiator on the outlet tank. I have verified that there is coolant coming out of those hoses, both front and rear.

The new radiator is a dual row, dual pass from Superior radiator also. It is about 3" larger than the one I was previously using from Brice Thomas Radiator which was a dual row down flow.

I have ran with factory recommended 187* thermostat and without, also have verified thermostat operation.

AFRs under load bounce between 14 & 16, if I look down while driving the average # I see on the wideband is 14/15.

Heater ports are plumbed into each other with a U style hose.

However with all of this, I cannot figure out why I keep having over pressure/overheat issues. The hoses get so hard at around 240* that they cannot be squeezed hardly at all.

I have other friends who run higher RPMs than me with front mounted radiators in endurance race rigs, without them overheating/over pressurizing.


I've tried to give as much info as I can remember, but I've been chasing this for months now. With a race in 2 weeks I HAVE to get it fixed.

Thank you in advance.

JoeNova

AFR between 14 and 16 under load is a major issue.
You're running lean, building excess heat. I'm surprised its not pulling timing from excessive knock.

indirocz28

iTrader: (7)

It's not knocking at all, and knock sensors are active.
Running on 93 octane.

After I do a block test this evening, depending what it does or does not confirm, then it will go to the Dyno shop.

indirocz28

iTrader: (7)

Block test doesn't reveal any combustion gasses in the coolant.