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79 LUV OVERHEATS AND AT THE SAME TIME MY HEATER BLOWS COLD AIR. Upon getting advice from this website i removed and checked my thermostat by putting it in a pan of hot water and it opened right as it should at 180 degrees so it is working fine besides it is a new one . Wile i had my thermostat out i reconnected my radiator hose refilled my system andd took a test drive to see if my truck would overheat or run ok with the thermostat removed. Driving with the thermostat out of the car it did not overheat, and not even reached normal temperature it was running on the cold side of about 1/3rd up on the temperature scale , and i did a 60 mile drive so it was a good long testdrive i also was getting luke warm air from my heater but it still did not feel as hot as it should have bin. About 2 hrs ago i reinstalled my thermostat and test drove the truck again and it promptly overheated it never boiled over but it is running extremely hot very close to boiling over, so upon the advice from this site i checked the temperature of the Coolant hoses. When feeling the large hose on top of the radiator the one coming from the engine it is very hot and when squeezing it i can tell there is pressure inside so the thermostat must be open and working also there is pressure in the radiator and the top of the radiator is also very hot, but the hose on the bottom of the radiator the one that is feeding water to the engine is cold and when touching the bottom of the radiator it also feels cold. Also now with my themostat reinstalled my heater is again blowing ice cold air even know the engine is very hot and when touching the hoses going in to and coming out of the heatercore the both feel cold so i am not getting any hot water to the heatercore. Also in the last couple of days i have flushed my engine serval times by disconnecting the hoses comin to and from the heatercore and hooking a gardenhose with lots of pressure to both of these hoses and thoroughly flushing then system. Also i removed my sparkplugs upon advice from this site and checked to see if one or 2 are clean and have white deposits on them witch would indicate a blown headgasket and i did not find any evidence of this the all had a even light brown deposit on them like the were burning good like the are supposed to. It is strange that the hose on the bottom of the radiator and the bottom of the radiator are cold wile the top is very hot. I would think that the hose on the bottom of the radiator and the bottom of the radiator itself should be at least a little hot or warm if the water is circulating like it should and i should always get hot water to my heatercore , It seems like there is a blockage somewhere however because i flushed the system so thoroughly serval times this is stumping me. Does anyone have any ideas Additional info- During all this going on there is no water in my engine oil i have no leaks from my radiator or waterpump and my waterpump makes no noise and the pully has no wobble like a worn bearing would indicate besides it is only 2 years old , When looking into the radiator cap hole i did not notice any water moving inside the radiator with the waterpump installed but without it in the truck the water is gushing fast like it should so the waterpump is working yet i checked both my old and new thermostat by like i said earlier heating it in a pan of water and the both were good even my old one does open at 180 degrees so i really did not have to replace it.

Dude, paragraphs. Learn to use them.

Also, Sentence structure is an important aspect of a good write up. doing so will allow us to help you in a timely and thorough manner.

Sorry, just giving you a hard time.


from what it sounds like, the water flow is being restricted.

have you noticed any coolant missing?

have you changed the radiator cap?

how about the mixture itself? Using straight antifreeze is a bad thing as it's meant to act as a corrosion preventer, lubricant, and of course an anti-freezing agent. The purpose of the water is to allow the heat from the cylinders to be absorbed and then dissipated once in the radiator.

You mentioned you flushed the system a few times and also flushed the heater core. When you reconnected the hoses and filled the cooling system, did you have the engine on? Having air in the system will cause this problem as well. (trust me, i've been there)

As a last resort, Have a shop take a look.

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To the Oquirr hills for awesome thrills! Go-go 4wd, Activate!

Maybe I missed it but with your engine in normal running order (themostat installed) are you losing any coolant?
Here's what i got,

No Coolant in the oil...good.
Are all your Plugs clean or just two of them? Check them all.
Your water pump is circulating coolant....the issue with the TOP hose HOT and the bottom hose is COLD when it's actually overheating makes me wonder about an obstruction in the radiator or flow.
Your Thermostat is opening when it should.
You have unrestricted coolant flow.?.?.?

Check your radiator cap to make sure it's holding pressure...or better yet....if you have a few $$$'s to spare just replace it to eliminate it as a possibility. Around $5. If it's not holding pressure your truck will run hot. You will usually lose some coolant with this issue.

Have you installed an overflow tank on your truck? If so are there any bubbles coming back up into it? If so then you have a blown gasket and it's leaking exhaust back into your coolant. You will also usually be losing coolant with this issue.

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In life there is the "Way things should be" and then "There's the way they are".

2005 Silverado 3/4T Crew Cab
1981 Luv 2WD
1979 Luv 4x4 Currently going through Open Heart and Cosmetic surgery
1995 Roughneck JetBoat
1981 Luv parts trk

I concur with the above post. If the one hose stays cold, it is not circulating properly. Try a new cap, it's cheap, if that doesn't do the trick, try this. Undo the bottom hose and see how long it takes to completely empty the radiator. If it takes more than a few seconds, it's most likely clogged. While it is cool, so the t-stat is still closed, you can take a pressure tester and leave the bottom hose undone, if it builds up ANY pressure on the gauge, it's clogged for sure...

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If you think no one cares, try missing a couple of payments...



FIAA!

SFPP!

Your radiator is full of crud, hot upper hose, cold lower are classic indications. Have the radiator boiled out and rodded. The heater may still not work the best because whatever stuff is in your radiator is also in your heater core.

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'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, rough body, bought new 12/4/78.
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch,more to come.

Like I said before, air in the system. You said that it didn't overheat with the thermostat out so that means it was circulating through the radiator ok, correct? Yes the radiator could be partially clogged and should be cleaned out anyway so I would do that also. However, top hose hot and bottom hose cold means no circulation because the pump is airlocked. I've had the best luck by filling the radiator, leaving the cap off, start the engine and loosen/remove a heater hose connection at the firewall until the water pumps out strongly. You may have to rev the engine a bit to get it out quicker. Make sure the heater control is in the hot position. Once it shoots out strongly, push the hose back on in place, refill any lost water and go from there. Of course do all this when the water is still cool to not scald your self with hot water. It is extremely hard to get all the air out of this engine at times.
This will get you going again. Now if this corrects everything for awhile but it starts to act like air in it again maybe days or weeks later, you are going to be replacing your head gasket. The gasket can leak air/combustion gases into the water jacket without leaking into the oil or any other symtoms.
I know all this because I repaired a ton of these when I worked in the shop long ago.
Hopefully this will be your fix.

a thought just occurred to me.

is your heater valve actually open? check the operation of the bowden cable and see if that changes anything.

_________________

To the Oquirr hills for awesome thrills! Go-go 4wd, Activate!

This seems to be an extension of your other post:

viewtopic.php?f=5&t=23962

If I read your post correctly, with the thermostat out, the truck doesn't heat up and you can see water flow in the radiator. With either thermostat installed, the truck overheats, and there is no water flow in the radiator. Is that right?

Quoting Sherlock Holmes' Law - After eliminating the impossible, whatever remains, no matter how improbable, is the truth. I think that, no matter how improbable, the problem is still thermostat related.

So, either you've got 2 bad thermostats (regardless of the saucepan test), or there is a installation problem with the thermostat. I don't remember, is it possible to put the thermostat in backwards on a Luv?

Or, is there something interfering with the thermostat? I've owned and worked on so many engines that they're all a blur to me, but isn't there a sensor in the intake that, if it's wrong, could interfere with the thermostat? I vaguely remember something like that in my rapidly failing memory.

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You went there in that?!?!

I still vote for a partially plugged radiator. Even a properly working and installed t-stat restricts the water flow somewhat- it's just the way it's designed. With the t-stat in place the decreased water flow is just not forcing enough water through the radiator to keep the truck cool. With the t-stat removed the increased flow volume does force enough water past the blockage to keep it cool. I would have the radiator serviced, replace the cap as insurance, or at least have it tested during the service.

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'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, rough body, bought new 12/4/78.
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch,more to come.

Find anything yet????

_________________
In life there is the "Way things should be" and then "There's the way they are".

2005 Silverado 3/4T Crew Cab
1981 Luv 2WD
1979 Luv 4x4 Currently going through Open Heart and Cosmetic surgery
1995 Roughneck JetBoat
1981 Luv parts trk

Having endured this issue over the years, I will offer up my almost worthless two cents. If the system cools fine without the thermostat, my logic says either the thermostat is the blockage in your system or the small restriction it creates is adding to some other blockage making it seem like the thermostat. You seem to have eliminated the thermostat itself so I would try what I had to do. I unhooked my heater hoses from my engine and tested flow throught the heater system to ensure it was clear, then Did the same for the engine block, then radiator. Those were all clear and flowing well. I checked how much water the water pump would push and it turned out to be the problem. It seemed to turn at normal speed and all that but didn't move the coolant very well.
Many of the ideas others posted up seem valid especially air in the system and the heater control valve. I don't run a valve since mine failed and leaked most of my coolant out on a roadtrip. I made a connector for between the heater hoses with copper pipe and haven't had an issue since. Please let us know what you have found out as many of us have dealt with the overheating issue and I am always looking for new solutions to that same old problem.

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Tact is for people not funny enough to be sarcastic.

The key to this whole thing here guys is---OP said when it overheated and the heater blows cold air at the same time.
He said after replacing the thermostat and refilling with water it still did the same thing (no heater output).
This is a water circulation problem, it has nothing to do with the thermostat or the radiator.
It goes like this: when the engine is running the water pump circulates water from the block, through the heater, and back to the block, around and around again while it warms it to about 180 degrees. At this point the thermostat opens and allows some of it to go through the radiator for cooling. So--no heater means no circulation which means two things---air trapped in the block (most likely) or a failed water pump (less likely).
Air gets trapped in the block until the thermostat opens, thats why it worked without the thermostat temporarily, air expelled itself out through the radiator cap.
Botton line is air shouldn't be getting in, in the first place, thus it can be the head gasket.

It doesn't appear the author "Hammerman" is interested anymore...at least he hasn't posted a reply since the original post and he has recieved alot of advice and ideas he can try. It's always frustrating to get a post like this and get NOTHING back from the author. I'm always curious to see what the end result comes out to be.

_________________
In life there is the "Way things should be" and then "There's the way they are".

2005 Silverado 3/4T Crew Cab
1981 Luv 2WD
1979 Luv 4x4 Currently going through Open Heart and Cosmetic surgery
1995 Roughneck JetBoat
1981 Luv parts trk

X2. Yeah you never know if you were able to help or not. I think it is a common curtesy, and that is how we all acquire knowledge on here.

If members with knowledge took the time to help I think a reply is needed.

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Certified pilots, looking down on people since 1903.