Coolant flow help!

Buellstunter · Aug 3, 2013

So I recently flushed the cooling system to try to revive my oil cooler. While I was at it I replaced the fan clutch due to a fan speed sensor code I was getting. And I also replaced the thermostat. Long story short it def. helped my deltas. Only a 10-13 deg diff going down the highway at 70mph. Was about a 40deg. Diff. Before. But ever since I did all the work the EOT has run between 192-198. 2 days ago I put in a coolant filter system and my deltas went from a 10-13 deg. To about a 25-31deg spread.
So Today I removed the 3/8 return hose going from the intake manifold back to the degas bottle. And the hose barely has any coolant returning to the bottle while the truck is running. Almost just a trickle. So I decided to
Pull the water pump. All seems well with the pump. Impeller is tight on the shaft and bearings are good in it. It actually looked like it was relatively new. (I've only owned this truck about 3 months) the other thing I noticed is the coolant I drained from the radiator is kinda like a piss yellow, while when I pulled the water pump, the coolant in the block looks like brand new green color.. Does anyone have any ideas what might cause the weak circulation, or can give me some direction or Something else I can look at? It also doesn't puke and the most pressure I build in the cooling system even after driving it hard is about 10-12 psi. Normally runs between 5-9psi. And pressure slowly drops off while the truck cools at idle????? I'm at a loss here. Need some help. :shrug:

G Racing · Aug 3, 2013

Coolant filter should not have changed anything. It's pretty much just a bypass system not full flow. Your oil cooler is probably plugged up again.

Buellstunter · Aug 3, 2013

That was my thought too. The filter shouldn't change a thing. However I did turn off the flow valves to the filter yesterday and continued driving the truck and the temps dropped back to about where they were. That's what led me to pull that return line and check flow today. My thought was I just don't have enough flow when I add the filter to the mix. Which tells me I barely have enough flow without it.

HeavyAssault · Aug 5, 2013

That small 3/8" line off the intake manifold is nothing more than a vent for any air in the system. It's not part of the coolant fluid flow circuit. The same applies to the 3/8" line off the top of the radiator. Sure they flow coolant but that is not their purpose.

I'd check over the coolant filter install work first.

Buellstunter · Aug 5, 2013

Thanks for the input. Did not know those two lines were just vents. I thought it was a return line to degas bottle that was supposed to flow coolant. Is it possible to trap air in the system? The Coolant filter install was pretty straight forward, since its a bypass system. Replace 3/8 radiator hose from degas bottle to radiator with new supplied line "T'd" off to coolant filter. Cut heater hose on pass side of the engine between heater valve and metal suply line and install coolant filter hose with "T" fitting inline. That's how it's hooked up.
I ended up putting a new water pump in. The one that was in had a plastic impeller and was 98 mm. The new one I got was an aluminum impeller and was 100mm. Seems to keep my ECT between 192-196 again. Looks like the oil cooler is starting to clog up again though, The spread is at 21deg. This truck has been a nightmare since I bought it 3 months ago. Just trying to catch up on all the neglect it had. Thanks again.

HeavyAssault · Aug 5, 2013

When I do any work to the coolant system I will burp the degas bottle a few times. Just drive it for a week, burp it, drive a week burp it.

I didn't think you could run the larger water pump without a new front cover.

Buellstunter · Aug 6, 2013

At the risk of sounding completely like a moron here, When you say burp the system. How exactly do you do that? I have Been monitoring my cooling system VIA a pressure gauge. It's inline on the vent hose from the degas bottle to the top of the radiator. I have been getting the truck up to temp. then slowly relieving the pressure in the system. then re-tightening the cap. Is that what you do?