Very frustrated.... temp needle swinging woes still!!!!!!!

Ok, so here is the entire story.

And just FYI, it's very easy when replacing the temp sender to also accidently unhook the fuel injector by accident. Makes the truck run funny, but it does run and throws no codes, just thought I'd share.

Ok, so anyway, to begin with I had a overheating issue. Many flushes later I was able to save the radiator and all had been well. About 2 weeks ago now I finally switched back to using Anti-freeze and everything has gone south since.

When I first switched i also replaced the sending unit for the temp needle, becuase at times it would swing some, worked like a champ for about 3 days.

3 days after switching to AF I walked out and found a puddle under the truck,(I found it seems to be leaking from what seemed at the time the middle of the radiator) I put some pepper in per many suggestions on many places I googled and drove onto work, my temp needle wouldn't sit still. Once it started to rise, it rose all the way to M/A, then fell back to N. Then kept swing back and forth the whole way. It would sit on N/O for about 5 seconds, rise slowly to M/A, stay there for about 3 seconds then fall back to N/O. Rinse, repeat, does this non-stop.

So, THIS weekend, I fired the truck up so I could use my portable air compressor to air up the car. While it was idleing (about 5 mins) I hear the sound of falling water, look over and coolant is pouring out of the radiator. Shut her down, pick up a new radiator and pull the old one. It's blown out the plactic on the inside of the tank right above the drain hole.

I replace the radiator and the thermostat that I had thought was clogged (causing my needle problem), and when I tested it out, still doing it, exactly like it was before. I also replaced the sending unit again just for giggles, still exactly the same.

It's so regular of a swing up and down, you could set your watch to it. It does slow down and speed up based on what seems to be RMP's. In other words, it stays still longer, and moves slower at 45 then say 75. But heat builds slower too.

As a side note, it has something to do with the stat (if the needle is correct), because I can go drive 200 miles and grab the radiator cap and it will be cool, and the tank will not be very hot, but the heater loop side of things will be hot as hell.

Only ideas I can some up with is my temp gauge needle went south at the same time the leak started, OR i have bubbles somehow in my coolant. I have no smoke(steam) in exhaust, no water in the oil or oil in the water. And when I burp it I can leave the funnel in forever and no bubbles come up, also no bubbling into the over flow.....

I'm stumped.....

Replaced so far: Radiator, temp sending unit, thermostat (2x)

*bump*

Ben Stein says "Anyone? Anyone?"

I have had the same problem for several years. My temp gauge does the dance like that all the time, but it never overheats even when I'm out wheelin'. I also think it's a problem with an air pocket.

Could there be a problem with the water pump?

ExploringNC said:

Could there be a problem with the water pump?

Click to expand...

I've thought about that, but I don't think so. From what little I can see the pump is pumping decent. I get currents in my funnel when burping and that tells me the water is moving pretty good.

Rick, I keep coming back to bubbles, it just seems to make sense. The air pocket forms there above the thermostat and the temp rises until the air pocket gets pushed through the stat (once it finally opens), OR the air pocket causes the sender to see higher temps until it gets push through. Not sure why this would be, but it DOES make sense...

I'm kinda thinking it's a sender misreading becuase of the air pocket though, because last night I did an experiment. It was COOL last night, so I needed the heater. I "tested" the air (with my hand) and the temp didn't rise or fall with the needle one bit, didn't seem to change at all. I would think if the block side of things was really climbing from like 195 to 220 or whatever you would feel the heat get a bit hotter I would think. ( I know I know, very scientific)

But, new developments, I still had a leak from the connection to the water neck (T-stat houseing) and the upper hose. I had taken it all apart to inspect everything and the old stock clamp style umm..clamps didn't have enough "hold" to them anymore to keep it from leaking. I didn't discover this until I was at work yesterday and saw the huge puddle. I messed around with it and only made it worse, so when I got home I stole a worm style clamp from my Trans Am and fixed it up...

So on the way to work today, it rose once....twice... then stopped and acted normal, first time in like 2 weeks now. WTH? Soooo... maybe it was the leaks? Since this started, I've had a leak, first in the radiator, next in that hose, could it be possiable that the leaks were causing it to get bubbles? Or the lack of pressure due to the leak maybe? IDK, but the hose leak was SMALL, and at first my radiator leak was small also. But it had been growing. We'll see if it really is solved or if today was a fluke.

Rick, question, what type of stat are you using?? Are you using the Stant Superstat style with no weep hole?

I don't remember what I used for a thermostat when I put my engine back together after the head job... I replaced my water pump thinking it would help with the problem. Didn't do a thing...

I was thinking about giving something like this a try: http://www.summitracing.com/parts/MOR-63745/ Might be able to get a better fluid fill.

I had this issue on a 96 GMC Burb 2500 it was the t-stat FWIW

In the past, if I used my funnel method (my burp in the sticky at the top of this section) I wouldn't have this problem...for awhile. About a week after refilling the system it would do it once when it first came to temp every time it sat for awhile. (I'm guessing bubbles would collect at the temp sending unit/T-stat area as it sat) but once it swung that once it would not do it again unless it was really cold out and I was going like 45 mph, then it would swing then.

I've always thought it was the T-stat opening and closing because it was so cool it was allowing the T-stat to close 100%, then the temp would jump because the T-stat had closed and it would take a moment for the T-stat to adjust again.

But I've had the cool day problem with two different kinds of stats now. So IDK.

Also, in the past it was just the first time coming to temp, and maybe once right after, then lvl as you could want. (like it did this morning).

I'm still coming back to the possiablilty it was the small leaks, allowing bubbles into the system as it leaked out slowly, but I haven't seen other people with this problem when they were leaking.....

Maybe it depends WHERE the leak is?? I've also noticed I would get swinging a bit if the overflow had ran dry and there was "air" at the top of the radiator. It made the cold day problem worse....

Rick, do you lose ANY fluid... maybe a slow leak that drips somewhere you can't see it is causing your bubbles and that's why you are getting what I am.

On the original stat, I had a solid gauge needle. When the 'stat finally failed by getting stuck closed, I replaced it with a cheapo autozone 'stat since I couldn't get an OEM or Napa stat at the time. The 'stat was thin and dinky, with a thin spring. Water pump was also changed since a squeaking noise made it think it was on it's way out. New to me, the temp gauge would creep up over to the right side some before letting go, then going back to about the middle, BUT it would still go left to right depending on the engine load, highway or city driving, and was never as solid as the factory 'stat.

Now that I've gone back to Motorcraft 'stats, the gauge is solid once again. I've never had a problem with cooling system bubbles, I just fill it sllllloooowly, sometimes rocking the whole vehicle front to back to get any air pockets out, then fill the coolant reservoir, take it for a spin until the 'stat opens, wait until it cools down, refill the reservoir, then keep some coolant on hand to top it off until it stays topped off. This method has worked for me on every vehicle I've had and I've never had a problem.

I'd say it's GOT to be the 'stat.

Mine does it too, but the engine is not over heating.. I don't worry about it anymore.. I too can go a week and it work perfectly, then it will act crazy, without trying to fix anything.. Every older truck I ever owned had its on demons, Ive chalked it up to that, until something breaks, I'm not gonna sweat it anymore..I do get less of a swing with a 180 degree t-stat than I do with the 198

I couldn't get a motocraft stat, I tried, nearest one was about 2 hours away, the 4 LARGE Ford dealerships close to me didn't have it.... And I HAD to have it that day....

Anyway, except for it's old first swing in the morning, since I've fixed that upper rad hose leak it's been fine. It's does move around some under load Like from Top of O to bottom of R, but that's it. Seems fixed for now....

Before it was swinging from one end of the gauge to the other every 20 seconds or so, like a clock hand almost, so it wasn't a load issue.

Just an update, once I fixed that upper radiator hose leak it been acting "normal". Just the 1 swing first thing in the morning, then fine for the rest of the drive.

On another note, I still have a SMALL leak from the lower hose, even after swaping out to the worm gear style over the stock clamp style.

I had been having a little trouble getting it real tight, becuase the angles were all wrong there on the bottom hose, so this weekend I'm going to try and get another turn or two on it and see it that solves the leak, AND the 1 swing each morning issue...we'll see.