I'm new to this site and need some advice or opinions.

I have an 86 f150 4.9L 300 cid and about a week ago it overheated, I notices it was spitting coolant out of the first freeze plug closest to the front of my inline 6. I took the carb, intake and exhaust manifold off and replace the plug. The intake has a large cracking in it so I bought a new one and replaced that as well. Put everything back together properly and topped it off with coolant. Started up the truck after getting her all back together and it idled horribly at first. So as I was burping it I let it warm up to see if I had fixed the issue, we'll I don't think I did. It blew coolant out of the open radiator neck like a gieser and had a bit of white smoke coming out from under and behind my carb. Also it still overheated so I shut it off but not sure where to go next. I really hope it's not a blown headgasket, I checked the oil color was pretty dark so I drained the oil and filled it back up but haven't done anything else to it. Any thoughts as to what it could be?????

 

Others will comment so I'll offer a little. Did you replace the T-stat? That should be done, no questions asked.

You refer to burping the engine and meaning to get the air out of cooling system/engine block. Best way, remove the highest heater hose at the T-stat housing, not the one to the W-pump inlet. Fill the radiator till coolant comes out the the fitting. Now your engine block is full, reconnect the hose and continue filling the system. You may have some air trapped in heater core circuit but it should work its way out. Fill the expansion bottle to between cold and hot full. Make sure the port and hose from filler neck to bottle is clean and not obstructed. If you don't have a tester, install a new and correct Rad cap

Reason for geyser, coolant in block was not high enough to open the T-stat, if it would open (T-stat being bad) and boiled the coolant blowing it back up the radiator.

Leaking freeze out plug? Was cooling system in bad shape, like lots of rust and deteriorated the plug?

Hopefully the smoke you saw was spilled coolant/oil burning off and don't look for a blown head gasket until all other possibilities have been eliminated

 

Ok so I DID replace the master sensor the t-sat sensor, its definitely seen better days. I filled it up with coolant like suggested, I have not replaced the spark plugs yet but I can. And I started it up and let it idle which after replacing the t-sat sensor it idles perfectly now. THE BAD now lol it STILL takes the gauge to the overheat mark and I turned it off and had smoke coming out of JUST the carburetor but it was coming out like a heart pumping blood, it would billow out a bit then reside then billow out and reside it did this for about two minutes till it was almost all out of smoke. Not sure what is causing that. Or the overheating still

 

Two things. You say master sensor, t-sat sensor?? Are you referring to the Thermostat or the sensor that sends the signal to the gauge on the dash or both items. If you did replace the thermostat are you sure you didn't put it in backwards. I'm not trying to be funny here, but I don't know your capabilities and yes, T-stats have been put in backwards. Spring side to the head and flat surface toward outlet neck to upper hose. NEVER REMOVE RAD CAP FROM A HOT ENGINE, YOU COULD GET SCALDED.
You could have a bad water pump also.

Smoke out of the carb or from around it?

You could run it again till hot, shut down, remove spark plugs.Have someone crank engine over while you watch, safely away, for any coolant coming out a spark plug hole. Also as it warms up are you getting, like, steam fromthe tail pipe?

 

I have a 86 with the 4.9 and manual transmission and it keeps overheating I have changed the water pump the thermostat and flushed the system for hours. It runs fine when idleing but as soon as I start to drive it overheats within seconds but ideling it will run all day no over heating. I pulled the therostat out let it run freely and ran it up and down the rd no heating I tested the thermostat by boiling water and it's fine so I don't understand why with the thermostat in it keeps over heating as soon as I move . I need help no one I know can figure this out and I love this truck and don't have the money to replace much more. There is no steam from the tail pipe and no coolant in ny oil I changed it just to be absolutely sure. And I made sure from reading this forum that the thermostat was in correctly and it was so that's not it either. Please help Ford fans!

 

Remove the radiator cap on a relatively cool engine so you don't get burned. Open the throttle rapidly from ldle to WOT. If coolant gushes out the filler neck you have a leaky head gasket.

Add a coolant recovery/overflow bottle if not equipped.

 

Welcome to the forum, david hatch! When it overheats, does it boil over or is it the factory gauge that is indicating the overheating condition?

 

So when I rev the motor up it doesn't blow out the radiator until I let off the throttle does this mean the head gasket is bad? And it's doesn't actually boil over because I just pull over and as soon as I stop it starts returning to normal running temperature but it gets all the way to the very last line of the temp gauge. I did use my friends radiator cap to test the temp of radiator fluid it has a built in gauge and it definitely was at overheating temperatures. It will sit and idle all day and never over heat but as soon as I start driving even backing out of the driveway it over heats. I can sit there and rev it up for 5 minutes straight and it never over heats either it's only when I drive. I tried running some cleaner thru it today it said to let it sit over night so that's what I am doing because someone said that maybe the head is plugged up with gunk from being so old.

 

before spending any more money or making any more guesses, i would get ahold of a compression gauge and see whether this engine is healthy or not.

 

sorry ... i didn't realize there were two people posting in this one thread ... even so, a compression test just might tell you something.

 

Ive got my 86 with 4.9 and manual trans in the shop getting some things done that im not comfortable doing myself yet.

My mechanic is replacing the fan clutch, he said its locked up and will cause overheat. Could this be your issue too?

 

I would like to know how he came up with that Granted it should not be locked up.


If I under stand how it should work as the temp goes and hot air goes across the clutch fan it should lock up till it cools down then free wheels.


Also if that was the case if a "locked fan" could cause overheating how about motors that don't have clutch fans, bolted right to the water pump, they should over heat then also no?


I did not read your post to see what your issue is and what you have done so far to try and fix it. But I think you need to look else were.


Just my .02
Dave ----

 

I know this is a very old thread but did you ever solve this issue? Mine is doing the exact same thing. New pump, new thermostat, compression test was great. I'm at a loss.

 

For anyone that come cross this post and has installed a new stat and has problems bleeding the air out, dont know why you would?
But if you drill a 1/8" hole in the flat part of the stat that will let air through and not hurt how it works.
When installing put the drilled hole at the top.
Dave ----