ChillOutWayne

I know this is general activies, but i need help desperately with this because this has been a project that has been going on way to long, and i need this in a place it will be seen by anyone. Thanks.

My dad own a 1996 E-150 with the W351. The thermostat stuck a few months back and caused overheating, and without notifying me managed to damage a head gasket. A few buddies and myself decided to make this a project and do a complete rebuild.

Anyway we have the van back together completely now, solved a few minor leaks that we had and today have been a driving it a few days. With temps in the 40-50s, i didnt think overheating would be an issue. So over the last two days ive watched it go thru heat cycles, watching the temp gauge drop a little to show the thermostat opening ect. So today i decided to take it on the highway, and gradually over a few miles the temp gauge went up, and continued to until i got off the highway miles down with the gauge between the A-L of "NORMAL", so about 3/4 of the way.

Now i know this isnt overheating, but its definetly hotter than it ran before, and im thinking with more miles on the h-way, it would have kept going up. So i got off the highway, and it gradually cooled down and i noticed the heat cycles starting up again, and operating normal. Then back on the highway and same thing, temp back up. I got off the highway to head back to the shop i work at to check for leaks and on the way the temp dropped some, but not all the way back down at a little under half way. Then after parking and letting it run, the temp went back down to normal and is cycling back and forth now completely normally. I am totally stumped, and im praying to God this isnt another breach somewhere causing air in the system.

BTW-the heads were decked ect at machine shop, also we did complete bottom end rebuild. Also replaced water pump.

Any questions to assist in helping, please ask.

TIA
Dan

SSlow 4.8

iTrader: (4)

Thats really odd that on the freeway that the temps go up... its fuel injected right? I wonder what the IAT's are at... that really shouldnt cause the temp to raise like your describing, but maybe it has to do with the induction system, im just gonna start with the simple stuff first. Wouldnt be an air pocket in a cooling line, bc you said it was normal when driving around town. Possibly just a faulty gauge?

On an old work van.. i think it was an 86 Chevy, sometimes this would happen everyonce in a while but eventually after regular driving it stopped raising temps on the interstate.

203Cree

Check your rad hoses. I know in the past I've seen the springs ( or whatever it is that gives the hoses their integrity ) inside the hoses would get really weak, especially after overheating. They'd get to the point that once the motor got hot and the t-stat opened, the flow and vacum would collapse the hose, restricting flow and causing the motor to run hot. Sounds wierd, I know, but it's worth a shot. Just give em all a good squeeze. If any seem particularly soft, replace em.

ChillOutWayne

I appreciate both of your responses, and both will be taken seriously and into consideration.

Im really on my last of nerves with this van. 2 weeks ago we started the tear down, had the motor out and dissasembled in one day, had the parts at the machine shop the next, and everything back within a week, all parts ordered ect. I then find out one of the engine kits was wrong, wrong piston rings in another kit, we scarred a cyliner wall...the list of negative things goes on.

Now finally we get it back together, in and running properly, just to find its still overheating, im ready to drop this thing in a lake.

Yes, the situation is very odd. Regular driving on the street the needle never even gets to half way, then after being on the highway for a while it started to creep up slowly over a few miles, then i got off the highway, the temp dropped down some and it seemed to go back into cooling cycles, then back on the highway only to find the temps going back up. Then a few miles off the highway on the way to shop and it slowly came back down, then sitting idling in front of shop it dropped and cooled properly. Im so lost.

Im wondering if its possible i have a serious problem here and that it really isnt cycling on the street in regular driving, and it just produces enough heat on the highway to raise the temp? Although i see the temp gauge drop suddendly when getting to operation temp, or a hair over, which im guessing represents the t-stat opening.

Im debating to pull the t-stat and try that, just to eliminate that possibilty. This t-stat is from Ford and only about 2 months old, but overheated many times during our issues before, i wonder if that effected it. The other option is the radiator. Is it possible that the flow is insufficient at higher rpms and the coolant cant dissapate enough heat to keep up with the produced heat?

Im going to check things out agian tomorrow after it sits, including radiator hoses. So all i need to do is squeeze them and see if they are soft? I know i replaced the upper and the bypass hose just in the last few months, but ill check the rest...

Im also wondering if i might have ANOTHER problem with the heads. The machine shop claimed they pressure tested them for cracks/leaks and i know i torqued them down right ect...but im wondering if it has something to do with increased pressure on the heads on the highway that may cause air to enter the system? GOD i hope that is wrong.

Thanks for reading guys
Dan

ChillOutWayne

Now that i thought about this longer, when we took the hoses off during dissasembly, the lower radiator hose had a spring in it, that was in 20 pieces, and we just pulled all that crap out and forgot about it, i wonder if thats a possibility...although when it got to operation temp today at work and i was under there, all the hoses looked good.

Ill keep ya guys posted, wish me luck

Dan

ChillOutWayne

That was one of our concerns before when attempting to diagnose the overheating before we decided to tear down. We though because it was reading so hot, and we didnt have leaks/air pockets/exhaust gasses(at first) that the gauge was just off. We also thought there was just one one temp sensor for both the computer and the gauge, but come to find out there is two. So we hooked up the shop scanner and ran it watching both, they correllated perfectly, all the way to 264 degrees

Dan

02-4.8

Replace the hoses(they're cheap anyays) and take the radiator out and clean it really good. Outside and inside. Could be bugs and grim built up around the fins on the outside, and gunk built up on the inside. Spray it don and flush it real good with a water hose. Maybe try a 160 degree 'stat to

203Cree

Get under and squeeze it. If you can collapse it by hand, that's prolly your problem. They'll look fine untill the t stat cycles.

ChillOutWayne

This i did do. I cleaned the outside, sprayed it down real good. Took a hose and flushed it thru for a while, but i suppose if there is hard junk built up that wouldnt get it out. Hmm..


Im gonna do that later on today. So even tho i can squeeze the upper all the way, and its brand new, that doesnt matter? Im just trying to get this straight in my head...

Thanks again guys
Dan

GMC_DUDE

This might sound kind of dumb, but you might want to check that the thermostat isn't installed backwards. I say this because I once bought a brand new 1983 Toyota Celica GT that had it installed backwards at the factory, and it behaved in a similar fashion.