Overheating

[OX1]

Running 200ish @ idle in 70 degree temps. The other day was idling close to 210. Can hear it bubbling after I shut it down.

All done within the past year......

Motor was torn apart and re-gasketed (including head gasket) due to really loose timing chain.

Parted a 76 auto, so I kept (and used) the 7 blade fan/water pump pulley.

Cheapo alum radiator we all bought when that deal came out.

Water pump looked OK when removed for re-gasket, so I reused it.

Engine runs awsome, hot or cold, has great power. No black or white smoke.

Thermostat changed several times just because. Last change may have been to a 180, have to check my receipts.

New rad cap. had a 12 lb, upped that to 16 lb. Has a pressure release on cap and it does bleed down if lifted, so I don't think it it a pressure leak.

Pressure tested system. Bleeds down very slowly over an hour or so.

The only thing I can think of is internal passages are partially blocked inside the engine/heads. I'd thought of using one of those flushes, but I don't want to clog up this brand new radiator.

Also, is it possible to get an air pocket. The last 460 I did had a huge problem getting an air pocket out, had to drill holes in thermostat which finally fixed it. I don't have lot of experience with old 302's.

I'm also not sure if that WP pulley may need to be changed, any difference between a stock 70 and 76/auto water pump pulley. I figured the 76 auto would be better, but forget now what they looked like side by side.

 

[70_Steve]

Fan shroud?

 

[OX1]

Fan shroud?

Yes, installed and brand new. Even checked to make sure I did not put the fan on backwards. Looked like it might be possible with the solid mounted fan.

 

[bblue]

it could be the distance between the shroud and the fan as well.

 

[broncnaz]

Head gaskets installed wrong? If so it will run hot no matter what else you try and do. Yes you can get air in the system but it is usually easy to work out and should work itself out if you have a overflow bottle.
No differance size wise in the water pump pulleys through the years.
Are you positive the guage is reading correctly? If its not getting any hotter than 210 then its really not overheating.

 

[Apogee]

When you tore the engine down and regasketed it, did you hot-tank the block and heads? It could just be due to internal scale and general fouling as you're not running all that hot really. I'd be inclined to put in a 195 degree F thermostat and let it run. 'Naz makes a good point about the gauge...how confident are you it's reading correctly? Mechanical or electric temperature gauge?

 

[OX1]

it could be the distance between the shroud and the fan as well.

I will check it, but everything is stock. Pretty sure that bling alum rad is no thicker than stock vs where the shroud mounts.

 

[OX1]

Head gaskets installed wrong? If so it will run hot no matter what else you try and do. Yes you can get air in the system but it is usually easy to work out and should work itself out if you have a overflow bottle.
No differance size wise in the water pump pulleys through the years.
Are you positive the guage is reading correctly? If its not getting any hotter than 210 then its really not overheating.

Pics of the gaskets

I did notice in the 3rd pic that one of the water ports is covered somewhat, but I don't think the gaskets are in wrong. They are felpro gaskets. It also looks like "front" is embossed in the right edge of 3rd pic and the front crank snout it right in the back of that pic.

I realize 200-210 is not that bad, but that was cruising lightly @ 40-50 MPH and nowhere near summer temps.
I do have an overflow bottle. Rad if full every time I open it with a cold engine. Does not seem to be excessive amount of coolant being pushed into the overflow until I open the pressure relief on the rad cap. It does suck that coolant back in when the engine cools back down.

When you tore the engine down and regasketed it, did you hot-tank the block and heads? It could just be due to internal scale and general fouling as you're not running all that hot really. I'd be inclined to put in a 195 degree F thermostat and let it run. 'Naz makes a good point about the gauge...how confident are you it's reading correctly? Mechanical or electric temperature gauge?

Did not hot tank anything. Had not had a huge amount of running time on the bronc since I got it (mostly idling), but it had not had overheating problems with it idling to make me think it needed it. I did have very little street driving on it since I initially had electronic ign conversion problems (and timing problems with a super loose chain).

I only tore it down due to the timing chain and trashing the teeth on the flywheel when my starter got stuck engaged due to incorrect wiring on the duraspark conversion. Everything looked pretty good inside, so I did not see any need for hot tanking. I've had plenty of engines that looked way worse inside and never had clogged internals to cuase an overheat. I really don't suspect it now, but figured I'd ask if the older 289/302 were prone to that (same reason I asked about getting air pockets, as some motors seem more prone than others)

I did use a Sears laser pointer temp reader. It read 198 pointed @ the thermo housing and where guage sender is mounted. Seems pretty close if the guage was 200-210. The cold side of the radiator was down to 160ish, so I'm leaning towards another bad thermostat, maybe just not flowing enough?? Would not be the first bad one I've had, maybe I'll try ford, as the NAPA one I got not that long ago was the same chinese junk the chains sell. I would hate to get one from ford and also have it be the same junk.

When I shut it off, you can hear it bubbling in the radiator (or somewhere), so it is definitely boiling or on the verge so that when I shut down, it starts almost immediately.

 

[phred]

I vote air pockets. Take the cap off, park it on an incline or jack up the front end and let it idle for a hour or so and it will vent out any air. Had that happen on several engines. Driving it around for some reason will not get the air out.

 

[Apogee]

Doesn't sound like a scale issue based on what you said, but the fact that you can hear it bubbling/boiling means that you're hotter somewhere than your gauge would seem to indicate.

What are you running for a timing set? Some timing sets are adjustable and can be installed straight up, advanced or retarded so what is yours set at? I know that my 429 will run quite differently and require different timing settings depending on how I install my timing set.

The new T-stat is probably a good idea, but I'd definitely test it with a thermometer on the stove before you install it. I've gotten way to many bad ones to assume anything when it comes to t-stats.

 

[OX1]

I will check it, but everything is stock. Pretty sure that bling alum rad is no thicker than stock vs where the shroud mounts.

Checked the fan to shroud depth.
Here is stock shroud and radiator.

alum rad and new shroud, looks about the same, but neither is set very far into the shroud.

Took a look at my stockish 79 bronc, which is stock in the fan/shroud/radiator and it looks more like the fan is half in half out compared to the edge of shroud.

 

[bludorbronc]

does it run hot with the hood off or open at stand still.check timing, carburetion, bottom hose have spring in it, fan half into shroud, shroud covering all rad, is fan big enough for shroud opening, did it do it with stock rad, does it do it with no thermostat. motor big compared to space around it for air to get out of engine bay.

 

[av bronco]

Did you happen to put a trans cooler in front of the rad. lately? I see you have a rigid fan(good) and no underdrive pulleys so it should run cool, the olny thing I can see is the w/p going bad or time for a hi flow w/p.(imop)update: I see you have a manual, never mind on the cooler thing.

 

[Viperwolf1]

The cold side of the radiator was down to 160ish

Doesn't seem like your radiator is doing enough to get rid of the heat. With a 195 degree thermostat and a 70 degree day my cold return is near 130 degrees. Could be poor flow inside the radiator, inefficiency of the fins, or not enough air flow.

 

[broncnaz]

Yep gaskets appear to be correct just making sure. I would say that your fan /shroud cleanerance may be factor. The fan should be at least 1/2 way into the shroud for the best performance.

 

[OX1]

Yep gaskets appear to be correct just making sure. I would say that your fan /shroud cleanerance may be factor. The fan should be at least 1/2 way into the shroud for the best performance.

Well, is it usually on stock early broncos?? Everything in the first pic was stock, except I have a 76, 7 blade fan. Did I forget some extra spacer or something??

Doesn't seem like your radiator is doing enough to get rid of the heat. With a 195 degree thermostat and a 70 degree day my cold return is near 130 degrees. Could be poor flow inside the radiator, inefficiency of the fins, or not enough air flow.

That does bring up a good question. These bling cheapo chinese radiators that many of us bought on that internet deal. Who is using one now and what are your results?

 

[Justafordguy]

I'm not sure if my aluminum radiator is the same as yours but it was a cheap one. My 302 never runs over 180 degrees and it's in the 90s here in Florida already. I have a 180 thermostat and everything except the radiator is stock. I think you have air trapped somewhere or your thermostat is still bad.

 

[broncnaz]

I would probably get a thicker spacer get the fan to within about 1" of the radiator it might help.
I have a aftermarket fan on my 73 but the fan sits almost 1/2 way into the shroud I could probably benefit from a longer spacer but I dont have any cooling issues. My bone stock 71 doesnt currently have a shroud installed so I cant really compare need to install that one of these days.

 

[gjrock]

I had a air pocket that drove me crazy. put the front end a couple " up and ran it with the cap off until it purged.