NicHoza

Hello everyone. For the most part my truck runs at about 200 - 215 degrees (a little hot, but I have considered this acceptable). Sometimes, however, the temperature jumps up to 225 or even 250, usually very temporarily, and then it will go back down to 200.

A while ago it would fluctuate like crazy between 250 and 180 when it was heating up, and I suspected the thermostat. I took it out to find that it was not the stock thermostat, but a dual-stage thermostat (which is supposed to fix the problem I was experiencing). I drilled a 1/16" hole in it just for good measure. It seemed to fix the problem. The current problem I am experiencing does not have to do with the time period where the engine is getting up to temperature -- it only occurs after it is up to temp. However, because of the previous problem, I still suspect the thermostat.

It also seems likely that there are air bubbles getting in somehow. The coolant level does seem to go down over time very slowly, possibly suggesting that coolant is dripping out and air is "dripping" in. I found a coolant hose that seemed to be wet around the edges, and tightened the collar, which wasn't very tight. For all I know that will fix the problem.

I still wanted to try running the engine without the thermostat. My reasoning is that if the rest of the cooling system works correctly, it should run cold without a thermostat. If the thermostat is not the problem (e.g., if the radiator is clogged), the engine will still overheat even without a thermostat. So I took the thermostat out, but then I realized a problem with this plan, which is that the thermostat seals the connection there, and without it the coolant drips out at a pretty good rate (with the engine on).

So I'm thinking I can try a couple things.

1) Cut out a gasket type shape from some sheet of rubber or something to seal it up.

2) Drill a huge hole in the thermostat and plan on buying a new one (or if the thermostat is not the problem after all, I could even weld something over the hole).

What do you guys think is my best plan of action? I also have a couple other questions:

A) What is the best way to take the thermostat out as far as coolant? I have just been opening it up and trying to catch the coolant that comes out in a bucket (rather than draining the coolant first or anything).

B) Are there likely going to be air bubbles when I put the thermostat back in? Will "burping" the system (run the engine with the radiator cap off, maybe even with the truck facing uphill) be good enough to get rid of these?

C) There is a drain valve at the bottom of the radiator which looks like it is possibly leaking. Could this let air in? There are also two little metal pipe-things at the bottom of the radiator with rubber caps on them, but the caps are all cracked and no good. I don't know what these are. Any ideas?

D) Has anyone else found that putting in a different thermostat (maybe rated lower than 88C/190F) works better? I already have a dual-stage one.

E) Do other people consider 200 - 215 degrees Fahrenheit acceptable? I have seen my truck run at 190 sometimes just randomly it seems, which is what it's supposed to be. Who thinks 210 will be damaging?

Sorry this is so long! Any help is appreciated! Thanks!

wyoming9

iTrader: (1)

As far as you know has the Radiator ever been changed???

After 20 plus years they do get blocked and around here it is not cost effective to have then cleaned.

FanClutch and water pump working like they should

I think I got a all metal radiator from Radiator Barn for less then $150.00

The two covered nipples you see are if you have a auto trans for the trans cooler. Which leads me to think the radiator was changed but who knows how long ago.

Thermo Stats are cheap just put a new one in and be done if you got the bolts out with out breaking your ahead of most.

To bleed the air I find the easy way is to put a flushing T in the heater hose close to the heater valve as that is the highest point in the engine . Remove the cap when you are filling the syatem.

To drain the coolant just crack the valve open on the bottom of the radiator

With what type of gauge are you getting these readings .

NicHoza

Radiator has been replaced with a "V6/Turbo 3-core Radiator" somewhat recently, although I'm not sure if it was a new radiator or a used one. The gauge I'm using is a VDO water temp gauge. What is this flushing T you speak of? I'm also not sure what the heater hose or heater valve is. Thanks for the info!

wyoming9

iTrader: (1)

I suggest you just spend a few hours for a couple weeks to understand the basics of what you have.

There is a 3 row radiator there very well maybe be a few V6 turbos floating around But they were all custom built with alot of Work and $$$

was your gauge installed when you bought the vehicle it is hard to know if it is even close to being correct.

With the new radiator water pump and fan clutch mine with a 195 degree thermostat runs between 175 to 185.

If you or a friend has one of those IR Thermometers it is easy to check your radiator for blockages.

A flushing tee can be had at any auto parts store it allows a hose to be hooked into the heater hose to flush the system. I use them to vent the cooling system.

The heater hoses are coolant hoses that allow water to flow to and from the heater core which is inside the cab.

the valve sits on the firewall and controls the flow of coolant to the heater core. valve closed no heat valve open heat or any place in between

NicHoza

The aftermarket gauge was installed by the previous owner. It would be good to get some confirmation that it's correct. Perhaps I could even try to fix the original temp gauge just to see if it has the same sudden increases in temperature.

I do have an IR thermometer. Looking for cold spots in the radiator then? That sounds like a good idea.

I put in a new $7 thermostat which is supposed to open at 180 degrees F, and the behavior of the temperature (according to the temp gauge needle of course) is completely different; it fluctuates between 225 and 180 as the engine heats up (a problem I solved on the previous thermostat by drilling a 1/16" hole in it). Once the temperature steadies out, the gauge shows about 10 degrees colder than the previous thermostat (which makes sense since the t-stat is rated 10 degrees colder). It shows about 200. Which makes me question my aftermarket sensor/gauge a little since it should be 180. I only went on a short drive, but I think I did see one or maybe two sudden increases in temperature after driving for a while (similar to what I was experiencing previously). So still not sure if these are from the thermostat or another part of the cooling system. I still want to do a test with no thermostat to make sure it always runs cold.

Once again, thanks for all the info!