cooling system trouble

I have had this cooling system problem for about 6 months now, right after I had the engine rebuilt.

From what I can tell the thermostat does not seem to open up and keep the engine cool.

For the past 6 months I've avoided this problem by ripping out core of a thermostat and putting that in so the water is constantly flowing. Doesn't let the engine warm up, but no over heating problems.

It's winter now so I tried to fix that problem and no success. When I installed a new thermostat there is no flow.

I've googled as many solutions as I can. Best I can say is there is an air pocket right behind the thermostat that is not letting it open up as pressure builds.

I'm about to buy a new radiator, though I highly doubt this is the problem since i have no flow problems when I had the thermostat with the ripped out core in it. I thought it could be that the guy that rebuilt my engine put the wrong water pump on it, but as stated no flow problems with a ripped out core thermostat.

Any one ever had this problem before?

note: I do have heat.

 

Try new hoses? Maybe worn out and collapsing?

 

I thought about that just still wouldn't make sense that everything flows fine wiht an open thermostat. I'm willing ot concede to the fact that maybe I'm purging the air out wrong, but I've tried everything i've seen online. Raising the front end, heater turned up all the way, 97 tacos don't have any bleeding ports like other engines do they?

 

How old is the radiator? I had an overheating problem with my 96 and it turned out the clogged radiator wasn't sufficiently cooling the coolant.

 

I've replaced many thermostats, but not the one on my Tacoma. Is it possible to install the thermostat backwards, so that the temp-sensor part is on the wrong side? That could cause it to no open up.

 

I just went through almost the same issue mine ended up being a brand new faulty water pump. I replaced the water pump and no more problems.

 

Drill a bleed port thru the thermostat washer area that touches water. 1/8" drill bit should do the trick if you have the room. I do this to every new thermostat on every vehicle I own to remove blocked air bubbles/purge the system when refilling. With the drilled hole, as you refill, it should force the bubbles to the soft side of the system as the water rises in the block. The small 1/8" hole wont affect cooling per say and you will always have a small amount of flow weather the thermo is open or closed to remove that trapped air that might build up.

How many miles on that original radiator?. You might have good flow as per the eyeball method, but the engine might need a bit more. Heater core could be blocked or the flow restricted if the coolant was mismanaged thru the years,,that would heat it up pretty quick.

New pistons with a rebore?. If so how thin did he bore the block cylinders? Thin cylinder heat up REALLY fast.

Seen a engine that was rebuilt and the guy had stuffed paper towels into cooling passaged to keep block paint from spraying into those areas. severe overheat situation once running. Once the paper towels were removed out of the passages,,all was well. Imagine that,,lol.

 

Hahaha yeah imagine that. I believe it's the original radiator with just about 200,000 miles on it.

The engine didn't get bored when it was rebuilt. I'm willing to drill the hole, do you have a picture on one you drilled?

I hate driving it right now but it's the only vehicle I have. I think the cold wisconsin air is helping me though. The gauge never goes into the red, but when I go up hill it gets close. I never go farther than 20 minutes at a time. So the sooner I figure out this problem the happier I will be.

 

Have you considered your temp sensor? Do you know for a fact that you are actually overheating? Maybe it is just a bad temp sensor that is giving a false reading to your gauge.

 

I've heard that their was another water pump that could be installed on tacoma, but it'd be the wrong one and thus wouldn't pump in the water fast enough. I'm hoping the guy that I had rebuild the engine didn't do that.

I am going to try to bleed it one more time before I start replacing things the expensive things.

So if anyone has successfully purged a cooling system of air and have any "make sure you do this" type advice please let me know.

 

thermostats have a bleed hole in the ring area that has to be at the top of the passage. it will have a little brass pin in it that moves around. If that's in right, then I would suggest using a vacuum tester for the radiator to pump any air pockets out before you go replacing things. If you don't have one or can't borrow from a parts store, I have used a shop vac to do it.

 

Not mine, but a similar situation of drilling a hole in the t-stat for purging air out. You want to get inboard enough to where the coolant is touching that flange and will allow the air to seep out as the coolant level rises during filling.

 

Yup. There are also 3 different starter levels when you choose a rebuilt starter. Low output, medium and high output. Couldn't believe that one. 1 starter for I4, V6, V8 maybe? I chose the high output and it wings the motor over much quicker than the factory one did. been going for many years on that one.

 

I stand corrected, Every one I have replaced had the hole already.

 

just wanted to share with you guys that drilling the hole fixed it. Seemed to be the only way I could purge out all the air. Thanks for the info.