Sorry, long post, but my trusty Ford mechanic has thrown in the towel and can't figure out my problem.

Started last spring:

1. Leaking radiator turned into replacing radiator and one of the thermostats.
2. Goofed around all summer with a great running truck and random coolant puking.
3. Decided to do an EGR cooler / valve delete.
4. Trip out to CO yielded a replacement of the upper rad. hose and both thermostats. Groove Ford in Denver quickly noted I was stranded a long way from home and stuck me for $700.
5. On way back to MN the seal between the front cover and water pump failed and Sterling Ford fixed it with EXTREMELY good service (and did it under my extended warranty)!!

My current problem is with heating. I warm the truck to ~100F in the AM and take off for work. When the coolant gets to 165F heater output goes to stone cold, not cool, but flipping cold. Stays that way until coolant reaches ~205F (which looks like the thermostat(s) open as temp drops to 194F). Heat comes back full strength. Except, if I slow down for traffic in town or stop for a light, then it trails off fairly quickly.

FORD says the EGR delete removed too much heat load and cooling system is now to efficient. My background is electrical, but that sounds like complete BS.

Also, the truck still randomly pukes and I swear I'm hearing my exhaust sounds coming out of the air filter. May be normal, but I'm so bucky at this point I've forgotten what's normal.

Mechanic thought engine sounded fine and said the exhaust thump was probably due to the tuner settings.

Thoughts?

 

Nope on the cooling system being to efficient, the system is huge to efficiently cool everything in the summer and makes winter's suck, but that's not your problem. It just takes these things forever to come up to temp in the winter.

You have heat up to 165 and then it disappears but the engine continues to heat up, so we have to think why that would happen.

I can think of a couple of things that I would check.

1. I know you've checked this but I would think a low antifreeze level could possibly cause that.

2. Is the hose going to the heater core hot when your truck is at temp but no heat blowing out. Is there a shut off valve going to the heater core for summer use/AC to shut the water going to the heater core off maybe working half ***??

2A. Is the truck climate controlled?? My climate control kicks on a certain min temp>>never really paid attention when that is but how do they achieve that control. Temp sensor for the fan to turn on, temp sensor to adjust the amount of heat, maybe a blend door or something?? Sorry I've never had an issue with mine so I don't know for sure.

Well, I think that's all for now, getting late, brain is numb, one other thing I just thought of, do you run a winter cover(Bra), I do and it doesn't do squat for helping with how fast it warms up BUT I have heard of the cover messing with the outside air temperature sensor (making it think it's warmer than it really is) would show on your climate control readout as a warmer than usual out side temp. The climate control system uses that outside air temp sensor in conjunctions with, I'm sure a fleet of other sensors to make us comfortable.
Just a thought???

 

could there be a air pocket in the cooling system?

 

Thanks for the quick replies. Easier one first:

Trucks been in twice to vacuum out any air with the other day being the last time. Also pressure tested and it easily held 30# for an extended time (not sure exactly how long they tested it, but said it was rock solid). Plus I don't see how an air pocket could be so consistent.

Mechanic said at one point he let truck idle for 1/2 hour plus and heater inlet hose was hot and outlet was cold. My first thought was a partially plugged core or like you said a valve problem. Mechanic indicated there is no valve in coolant line to/from heater core. He was going to back flush core, but after FORD said it was the modding and the hyper-efficient cooling system he gave up.

Being it's cold out and long days at work I haven't had any time to play with it myself.

Being continuously paranoid with this motor, I did order up a block tester just to verify head gasket integrity (due to the puking). But three different dealerships have messed around with it and all have said the head gaskets are fine.

I've never beat on it; over heated it; or had the boost higher than 40# so I'm hoping for good results from the block test.

 

Forgot, but.......

I watch the coolant level as close as I watch the EOT and ECT.

The level seems to always want to be at the lower tap on the upper part of the degas bottle. If I fill it up to the low level mark on the bottle it pukes.

The mechanic moved the radiator return line from this tap to the upper tap so the lower tap is now capped. He said that's the way it's intended to be and that the lower tap was for the EGR return line (which I don't have).

 

i know i am new to the 6.4 but i thought that the house with the updated T sucks fluid and if the level is lower than that hose it could suck air? also hows your coolant cap. the stock caps use way to light/small of a spring, compare it to a aftermarket one and you can see the difference. also 30# is kinda alot. are the caps rated at 16#? i know you said it held that pressure but it could be hard on things with that much pressure.

 

I've had two different Ford mechanics (different dealerships / states) tell me the return hose off the top of the radiator is just that, so it won't draw in air. If the bottle goes dry the hose on the bottom of the bottle would draw in air. Makes sense to me, but I can't say that's true beyond any doubt.

 

There are a few possibilities here...

One, is that you have a malfunctioning thermostat.
I am leaning away from that though, as it sounds like the temperture drops off rather instantly.

You mentioned coolant puking; and also mentioned a 30 psi pressure test. Well, I'm inclined to think you might have head gasket issues. A friend toasted his without any tuner or anything.

Let me tell you a story....
I bought a spartan tuner, and ended up puking some coolant. I put everything back to stock, and I could even rev the engine in the driveway cold, and it was puking.
My mechanic drained the coolant, put new coolant, and it still puked.
We kept draining, filling, new coolant, etc.

Eventually, it wasn't puking anymore, but then the EOT was getting way higher that the ECT. We kept fooling around, I took it to ford, more tests, more money.
We tried boiler cleaner, new coolant, running over full, running low, etc.
One side of the engine was running hotter than the other. That doesn't even make any sense.

Eventually, SOMEHOW, things just fell into place. No more puking, both sides of engine are within 1-2 degrees, and EOT is never more than 8 degrees over ECT.

It's been months and months now, haven't lost a drip of coolant, and she'll hold 40 PSI all day long.

The moral of the story, is that the cooling systems in these things is stupid, and unless you put a tinfoil hat on, you're unlikely to even understand.

 

Pull the termostats again. I think that is the problem. Replace both. And test them for proper operation before install.

 

The thermostats were verified to be operating correctly the other day at the dealership.

If I were to pull them, what's the setpoint for opening and is it the same for both? Looking around online I've only seen a value of 190F, which doesn't seem to support my observed temperature indications.

The block tester I ordered should be in the beginning of next week and I've been told that it's indication of head gasket condition is dead on. Anybody have any experience with this tester?

 

The Modding answer is BS, this statement tells a story right here.
Mechanic said at one point he let truck idle for 1/2 hour plus and heater inlet hose was hot and outlet was cold
Something not right here, Diesel mechanic I'm not, but I've been working on cars and trucks since I was 13 and I know that if that's a true statement something is FISHY!!!!!

 

I agree, I like the mechanic, but with the mods he's beyond his training. Even he said it doesn't make sense as the truck runs perfect.

 

I would seriously pull the t stats and check them. 190 or so they should open...just put them in a pan of water and have a temp probe at the ready.

Put them in separate pans.

watch them for when they open and see what you get.

Most tstats always had the temp stamped in them. Not sure about these as I have not had mine apart.

 

I have this same issue in my 08 and it just recently started. Early winter when temps were still low 30's and low 20's like now, it never missed a beat!

 

Fearing the worse (head gasket), I ordered up a block tester to verify my head gasket condition. I drove the truck home pretty hard (hit 40# of boost a couple of times) and then proceeded with the test.

Ran the test twice, fresh fluid each time, and absolutely no change in color from the blue tester color. What a relief.

Have a though I want to bounce off the masses. When I installed my EGR delete, I was a bit surprised by the simplistic o-ring / one screw flanges used on the coolant passages.

Any thoughts on the o-ring holding system pressure, but sucking in air when the engine cools?

I've heard of freeze plugs doing this, so if that were true, it seems this could certainly be possible.