The Stovebolt Site Forums The Shop Area General Truck Talk Why does my truck hate thermostats?

Okay, to start off, this truck was not rebuilt. We pulled it out of the barn last May & started it up after sitting for about 23 yrs.

It starts easily but takes a long time to warm up & after reading all the posts I could find, it doesn't seem good for the engine to be running mostly cold...decided it should have a thermostat.

Each time we put one on it over-heats. All the way to the h.

Started off with a 180 stat & 7lb radiator cap. Changed the cap to 4lbs-that's what it has now. Switched to a 160 stat. Overheated. Put a 1/8" hole in the side of it last Saturday(this one I put on myself )(I've never done much except change oil). Ran it 20 mins at home, let it sit. Took it on the road a while later & overheated in less than 3 miles.

Tomorrow Alberto's bringing a Hi-Performance or something thermostat with a larger hole. The other idea is to put about 4 holes instead of just one around the side.

Our climate is pretty mild but I'm going to need to use my heater soon too....

Is there something major we're over-looking?

Thanks in advance for any ideas.

Sabrina

Sabrina,

I'm going out on the old limb here, but that isn't new. My uneducated guess would be the cooling system is plugged up somewhere else, and WITHOUT a t-stat, it can overcome this problem. With the thermostat installed, it can't over come the problem...so it lets you know!

My first thought would be plugged tubes in the radiator. You can peek in the fill hole and see the top header and tubes. If they look like grampas veins, you need help.

I don't think the block in these engines plug much, so the next item to check would, of course be the water pump.

Please don't tell me you have a new radiator and water pump...I've had a tough day!

Stuart

is the "overheating" seen only in the gauge, or is the rad actually blowing off? if it's the gauge, it isn't necessarily overheating - when the gauge shows alla way to h, take yer candy thermometer and poke it in the rad to see the real temp - may just be a bad gauge or sender

Bill

Not a radiator expert, but could it be possible that the radiator is not building up enough pressure to open the thermostat? Is there steam billowing from anywhere when the guage says "H"?

Sounds like you have an air pocket behind the thermostat. Drill about a 3/16 hole in the flange of the t-stat to let the air out as you fill the system. It also helps to park it nose up on a steep grade to help bleed the air out of the system.
Good luck,
Scott

atomarc- Yup, completely rebuilt radiator & rebuilt water pump. I can see water movement when I peer in, is that good enough? When we flushed it in the begining we got a lot of black crud out of a spot down on the bottom of the motor on the driver's side.

Red58- When we stopped the second time on the way into town we had a big trail of water behind us. After I heat it up about 10 mins (at 6:30am) & then drive off to take the daughter to school with the needle just past the C, it nearly makes it to the middle of the gauge by the time we go the 3 miles to get there. I think it's sending and posting accurate temperature.

The compression in each cylinder is supposedly 120. Could the head gasket be bad (it probably is) enough to cause something to make it overheat with the thermostat?

I'm getting several new grey hairs every week on this one

Thanks, Sabrina

48bigtrucks- Alberto said the hole he put was 3/16 not 1/8 so that was good. We didn't drain the whole system so there was water right where I was putting it on. Could there be a pocket somewhere else, further in?

Sabrina

Have you checked to make sure timing isn't too slow? Is vac advance working properly?

Sitting that long some of the water holes in the head (or head gasket) could be stopped up and not lettng the water flow properly.

Even after flushing the block and head could have stoppage issues after that many years.

These are just a few suggestions I could think of, good luck.

48bigtrucks - Those are sure nice Loadmasters you have. Our '49 1 1/2 ton is sitting waiting for us to get it going again. We pulled it out of the barn in about '94 (after 20 some years), made it into a water truck & I brought all our water (for two houses) for about 3 years & parked it. Just what we said we'd never do :rolleyes:

Congratulations on two fine working trucks. Nice.

Sabrina

Thermostat in backward? the spring goes toward the block.
Was the radiator top and bottom removed and the flues rodded out, or was it just flushed and painted?
Is the fan close enough to the radiator and pulling enough air through the radiator? (it should hold a piece of paper on the outside just ideling)
Is the air the fan is pulling thru the radiator hot?

Roy Thanks. I'm pretty sure the timing is good. I have no idea what the vac advance is. I guess it's time for a search - fast. After finding all that gunk that came out of the head, I always figured there could be more. What I can't understand is how if there are stoppages, why does it run so cold without the stat?

Don Gwartney The radiator was completely rebuilt. I'm going to have to check on those fan issues. Should the air it is pulling be cool? We tried for a more-blade fan but didn't find one that fit. You've got me going on the direction of the thermostat. Alberto assured me to put the copper side down, flat side with the sensor and the pointy side up. Told me to call the mechanic if I still wasn't sure. Called & he said the same. I put the flat side down into the hole where the little recession is so it would be able to touch the water. Do I have it a%# backwards

Sabrina

If you stat has a spring on one side, then the spring goes towards the engine, the flat side towards the radiator. The stat won't open near early enough if installed wrong.

Roy- Now you've got me, which is not hard to do. I'm all mixed up now. The spring is on the side that is flat & the other side is the 'pointy' side that moves when placed in hot water. I put the flat side that doesn't move laying in the water of the engine. Is that wrong?

Sorry, of course it moves but it's flat & I put it down.

Sabrina

I guess it may depend on the brand of thermostat you are using.

Generally if it has a small coil spring on one end, the spring is wrapped around the sensor and has to placed towards the engine.

Some thermostats are made a little different, but the larger end usually goes towards the engine, and the flatter end towards the radiator.

Might help to know what brand thermostat you are using.

Here is a picture of some thermostats. Do any of these look like what you are using?

http://www.stant.com/brochure.cfm?brochure=2880&location_id=168

The coil spring is wrapped around the sensor and when it moves it moves through the case up towards the 'pointy' side. I had the sensor toward the engine.

The first one (180) was CarQuest brand, the second (160) is Stant. The fancy, high performance one he'll bring from the States tomorrow after work is Prestone and has a larger hole. It won't help much if I've got things upside down though :rolleyes: Am I okay or backwards?

Sabrina

Yes, most of them look like mine & that's the way I put it in. The way they are in the photos...Is that correct?

That's correct, looks like you'll have to go deeper to find the trouble. Sounds like something is stopped up somewhere. Let us know how things come out.

Will do. Thank you for your help. Since I'm not savy on most mechanical things, it's easy for me to get messed up.

Now I need to look into the Vac Advance system...maybe tomorrow...when I'm 'bright eyed and bushy tailed' and stand half a chance of understanding

Sabrina

Where is the water leaking from?

The information you are getting is correct about radiators and thermostats.

Do you have any idea why the truck was parked in the first place?

I have a suspicion, and it isn't pretty.

One of the old time fixes for a motor that overheats (and only in low pressure systems) was to remove the thermostat and/or the pressure cap. The reason that they did this was usually because the block was cracked. Any time you tried to pressurize the block, it would start leaking and overheat quickly. Removing the thermostat/pressure cap would allow you to run the vehicle quite a bit longer before it overheated - but it still would eventually overheat.

What you need to do is to run the motor with a pressurized radiator, but make absolutely sure you know where the water is coming from when it overheats. If the block is cracked, you should start seeing evidence of where it is. It can also show up in the exhaust as white steam, or in the oil as a sort of chocolate milkshake, or possibly white globs on the dipstick.

Hy Sabrina, With no thermostat water is constantly circulating through engine and radiator so much less likely to get too hot. With thermostat water is basically held in the engine until it reaches opening temparature of the particular thermostat,then the water is allowed to circulate from the upper water hose to the rad down through the rad rejecting heat as it drops down until it reaches the bottom of the rad where it is picked up by the water pump and ciculated through the engine again. If your getting steam from the rad and it is new I would suggest one of two problems may be the culprit, an air lock in the rear of the engine block or head, or an actual obstruction [crud buildup] in either of those two areas. You could try loosening your sending unit at the back of the head and making sure water comes out, if thats o.k. I think I would reverse flush the block, take the thermostat out and put your garden hose there, take the bottom rad hose off and direct it towards the ground, now flush water through the engine with the garden hose and see what comes out, this is done with the engine cold and not running, hope this helps.

Vaughn- The truck was my dad's & got parked one day to be used again in a couple of days & it never happened. By then they were just using it to keep it in shape.

I think the head gasket could be bad but isn't 120 a lot of compression? Is it possible to have a cracked head and that much compression?

I will definitely take a closer look at my oil. I haven't seen anything remotely white on the dipstick & my exhaust is blacker than the ace of spades but I'm going to pay more attention tomorrow. For sure.

When it overheated & water came out, it came out through the tube that comes out by the radiator cap onto the ground.

Sabrina

Sab, can you bypass the heater? to see if that may be the problem..

-Randy
*

3B- Well, Alberto reminded me that he took the sending unit out & we checked it with a thermometer in hot water & he also got all the crud out of the spot on the side. Flushed & reverse flushed.

He says the stat he's bringing is called a Power Performance by Prestone and has much more possible flow when open. I'll let you all know if that does it.

We've been talking back & forth by radio between these posts. He says there is no water in the oil, no white exhaust.

I think he is going to tell me my truck must be a female truck for making him stand on his head and rub his belly at the same time to make it happy

Thanks a bunch, all. I'll update next week.

Sabrina

Hey, Randy!

I'll see if he can do that. It has a faulty switch but I've heard it run but never used it. Should have a new switch this weekend too.

What will that do?

iowa trucks 59- Thanks for info about head gasket. Will look.

Four degree advance or retard on what? I know, I should know but don't. Timing?

The block drain you mention at the back, maybe that's the one we (he) cleaned (I watched). It was on the driver's side of the engine, down low & so clogged he had to poke at it to get it draining. When you say left hand side of the block, is that looking towards the radiator? If so, at least I'd be on the correct side