Heat and Radiator

[bosco200]

My heat in my truck wasn't very hot so I thought thermostat went bad cuz my gauge in my truck wouldn't work so I changed it and my gauge in my truck started working...but when it starts to warm up the gauge will start moving up and gets a little over half way on the gauge and it will start pumping some good heat out....then it drops goes back to the first line on the gauge within seconds and it doesn't pump out as much heat....The first thermostat was a 160 so I put the original 190 in....should I put a higher one in?

[cdowns]

getting a new original type at 190 would b best

[bosco200]

I did put the 190 in and that's what it did.

[70C10Toejam]

I would guess it is just a defective one. When it opens, its staying open too long.

[dammitmitchell]

are you running a fan clutch? direct drive?
what radiator did you put in?
a common issue after a radiator swap is an oversized radiator for the trucks motor.
another common one is that a radiator manufacture blends different sizes of radiators into one single model number. so lets say a v6 dodge gets the same radiator as a v8... when they need to be different sizes.


if you swap the thermostat again i would look either into replacing the radiator with a slightly smaller one or changing to a fan clutch or electric fan set up.
unfortunately somewhere in the system is over cooling.

[bosco200]

I haven't changed that radiator I just changed the thermometer from a 165 cuz it wasn't working then I put in a 190.

[Zeke's Garage]

To be truthful, if the thermostat is sized correctly, you can't 'over cool' the system. The thermostat will keep the minimum temperature to it's rated value by opening less. So if everything is working properly, the system will not vary below the thermostat's rated value, but of course can go over.

Make sure you've got enough coolant in the system, I've seen it where the temp guage and thermostat won't open because there wasn't enough coolant in the system to wet them and make them work.

Also make sure that both heater hoses are warm/hot to ensure there is flow through the core.

Shawn

[bosco200]

Ok thanks ill go check that now.

[bosco200]

Ok I checked the hoses and they are hot...I was watching my temp gauge and it was going up and it almost got half way then it dropped down to the line right after the C and the heat want as good.

[cparman]

here is my $.02 worth. You have a new TSTAT, and heater hoses that seem hot/warm. You have heat in the hoses and then it goes away? I might suggest that you backflush the heater core. Hook a garden hose to one side and run water thru the core until you see clean water running thru it. Hook the system back up, startthe truck with the radiator cap off, and run the truck until the temp gauge is in the middle. top off the radiator and shut the truck off. let it sit for a bit then restart it. Your description is kind of like there is air in the system. the above will ' burp ' the system. hope this helps

[bosco200]

Ok thanks ill try that in the morning.

[bosco200]

Ok so this morning I took the heater hoses off and flushed water through them....it was brown when it was coming out.....I put more antifreeze in and ran it with the cap off and it started to boil over so I turned the truck of put more in and it looked like all the air pockets came out cuz it was gergelling a lot....So I capped it....ran it....the Temp gauge got a little over halfway and was pumping out great heat....then it did the same ol thing and dropped down to the line right after the C....So I just shut it off put my tools up and that only took me about 45 seconds....got back in started it up...and what do you know it starts climbing back up...it get a little over halfway and holds there for about a minute...then dropped back down....I don't get it?????

[Zeke's Garage]

It sounds like you still have air in the system.
Normally I'll run the truck with the rad cap off until the thermostat opens (you'll feel the upper hose get hot). Usually once the tstat opens, the level will drop in the radiator, and you can fill it up more.

So unless you've got the system setup in a really odd way, once you get all the air out, it has to work properly.


Shawn

[70C10Toejam]

Any luck yet????

[bosco200]

No it still just goes back down to the line just after the C.

[70C10Toejam]

Don't know what to tell ya after these suggestions other than to pull the 'stat and test it in water. Use a thermometer and heat it up till it opens, then cool the water to see when it closes.

Last winter mine wouldn't get above the shaded area unless I covered the radiator. New 'stat with new rad this summer and it goes to the middle of the gauge. It does drop a bit when the 'stat opens, but then returns to the middle.

[PanelDeland]

Mines always run just about 3/8 of the guage.I replaced the original 6 cyl 2 row rad with a 4 core V8 about three weeks ago.If anything the heat is better.I can sure tell the diff thru the rad though.The hot coming out keeps that tank too warm to lay your hand on but the other side is just warm enough to keep your hand comfortable in the 20-30 degree weather we're having.Once warm the guage has never moved more than just enough to see,with either rad.

[vortech71chevy]

I would invest in a nice thermostat, not one of those cheap stant ones. Ive had alot of problems with them sticking open (which sounds like what may be happening to you) or not opening at all. From summitracing you can get a nice stewart warner 195 or something for about 15 bucks, and ive yet to have an issue with those. Also, once you get your engine operating in the correct range, its important that you have your hoses routed properly. The inlet for your heater core. should be connected to your intake manifold to get the warmest possible water flowing through it soonest, and the outlet to your water pump/radiator/anywhere-but-the-intake.. Good luck.
Posted via Mobile Device

[dmack91]

OK, Dumb question on heater hose routing (don't mean to hijack but it seems relevant to this thread).

Does the hose to the top of the heater core go to the water pump or intake? Mine was bypassed and I just installed a new core. Want to make sure they are routed correctly.

Thanks

[vortech71chevy]

i have the top to my manifold, bottom to my water pump... works great.

[dmack91]

Thanks, sounds like I have them on backwards.

[Zeke's Garage]

From what I understand, you should have the bottom hose connected to the pressure side of the system (manifold) and the top going to the return (water pump or top of radiator). Apparently this keeps the core full of hot water and allows for better heat transfer... But honestly as long as your system is full like it should be, it really shouldn't make any difference which one goes where.


Shawn