Heat works, but gets only slightly warm

[n8roro]

Should I flush the heater core or replace the thermostat? Is there another possible problem?

 

[Drock]

Well both would be a good idea regardless. Do you have a temp gauge? Is the engine getting up to temp? You may find there isn't a thermostat?

 

[n8roro]

No temp gague, but I would like one. After driving an hour or so it still is not blowing hot air. The manual says there is a thermostat. Do you mean someone removed it?

 

[sneekyeye]

Id flush the heater core first, just take off those two hoses at the block and put the hose in it both ways. There should be either a 180 or 190 thermostat in it. Someone could have removed it, who knows really.

 

[Drock]

No temp gague, but I would like one. After driving an hour or so it still is not blowing hot air. The manual says there is a thermostat. Do you mean someone removed it?

Yes there's supposed to be a 195° thermostat. But, yah know people do silly things with vehicles, like take out thermostats.

 

[PeeWeeQ]

I hate to say it, but, start real simple and make sure your full with coolant. Low coolant means you've got air running through the system and air doesn't carry heat like liquid does...

I always like to start with the dumbest, simplest thing first, then work my way to the more complicated/difficult. Sometimes, if I don't know that something has been maintained or the last time it was replaced, I might just do it if it's in the budget simply because it can't hurt with as old as these things are...

Just my ...

 

[Tinstar]

Perform the above mentioned recommendations as needed.

But also make sure your heater blend door is closing all the way.
It’s behind the glovebox.
If it’s not closing properly, it’s also letting cold air in and that’s why it’s not as hot as it could be.
I had the same issue after getting truck.
Easy fix. Just adjust (bend) the wire from the heat controller on the dash to the door.
You’ll see what I’m talking about when you remove the glovebox.
Mine is nice and hot now.

There are several threads about that issue already.

 

[cucvrus]

I do NOT want to add fear to the recipe of repairs. But a simple thing like no heat can also be a head gasket issue. I would get a pressure tester and check the cooling system. Sometimes it will hold pressure and still be the head gasket. I had an M1009 that would hold pressure for days. But one of the symptoms was no heat. And then it would get heat at highway speed and stay nice and toasty. But in city/town driving lower RPM's No heat. Also the coolant recovery reservoir would be full of coolant every day. I would unbolt it and pour it back in the radiator. Not to scare you but keep that idea in the back of your head. I have been removing the heads on any CUCV's I have apart for rebuild. So far 3 have needed head gaskets and they were good running vehicles. Just that 30 years and acidic anti freeze is taking it's toll on the thin steel head gaskets. Head gaskets are much better now then they were 30+ years ago. Doing the heads is not a real big deal as long as you don't have a set of cracked heads. Gaskets, bolts, and get the heads checked out at a good quality machine shop. No need to add studs and get out of budget. It is a very reliable engine and it is old school. Simple. Remember to keep this acronym in mind every time you work on your CUCV. KISS "Keep it simple, stupid" because of the simplicity it will just keep going in stock form the way it was designed to do. Think about it. Everything you change and convert thinking you are making it better and more reliable has already lasted over 30 years. So as a rule. If you can't unbolt is or unplug any modification you are thinking of doing. Don't do it. OK enough of my gloating. I just found over the years to keep looking until I found the problem. NOT change everything that leads me towards it and create more issues and spend fool's money on the issue when it is already there and I am trying to avoid it. Bad head gaskets don't go away. But please do check for them and pay heed to the results of the diagnosis. Have a Great Day. it is pouring down rain in Pennsylvania today. Time to rest.

 

[n8roro]

So it sounds like I should go ahead and replace the thermostat and do a heater core flush after I check the blend door. If the issue remains it would be the head gasket. I will read up on replacing the head gasket, but it sounds like it is a manageable project to do in a home shop. Thanks for all the help. Fingers crossed.

 

[cucvrus]

If you have a home shop. I would pull the engine and go over the entire thing. It is much easier on the floor of the shop and you can do a thorough job. Check out my Easter Find M1008 thread. i done several on the floor. I even have 2 engine stands and the floor and wood blocks work better.

 

[StoneyHill]

Has anybody tried one of these factory brass heater cores from Summit racing:

https://www.summitracing.com/search...toview=SKU&sortby=Default&sortorder=Ascending

Mind is leaking and I have not heard good things about the parts house aluminum ones that are in stock. The item says "with AC". Will it still fit?

SCott

 

[StoneyHill]

I just found this suggestion from another thread:

http://www.autozone.com/cooling-hea...r-core/pro-source-heater-core/459245_0_0_6774

Has anyone tried this one? Or should I just use the spectra premium that has been mentioned in several other threads?

 

[cucvrus]

I never had any trouble with plastic aluminum, all aluminum or copper brass. They are just a heater core. I know several members here have heater cores I installed. I use parts from who ever is open at the time of my needs. Most times Autozone is open when I need something I buy it and it works and fits well. It is just a thin metal vessel hat water flows thru. It has a fan that blows over the vessel and transfers heat. It is not a flux capacitor or a nuclear reactor. It fits tight in the box and clamps in securely with no sharp protrusions. Put it in and run it. When I am driving in cold winter weather I never think "Boy it is nice and toasty in here. I just wish I had an OEM heater core" Most things you buy are warranted and it's your truck buy what you want. If it fits and works use it. Now if you have to cut wires and change things I see a RED flag come up. Have a great day. Stay warm and get the heater core wherever you can buy one that fits.

 

[Drock]

I just installed an aluminum heater core about a month ago, and it works fine? The only issue I've read about, is some are too thin and don't fit in the air box tight enough? I got the part number off a thread on this forum. here it is (Spectra Premium) #94553

 

[stanzuray]

When I first got my CUCV and was working out the bugs it had very little heat even with cardboard in front of the radiator. I figured it was because it was a diesel engine and I'm in cold Alaska fall. Then I saw that regular Chevy thermostats get put in some times and the CUCV needs one that looks like a hockey puck. I got the right kind and like magic got all the heat I need and takes about 3 miles to start putting it out. Just one of many things to try.

 

[StoneyHill]

I guess I am way overthinking this issue. I just do not want to do all the labor any more often than possible.

I appreciate everyones help/opinion

Scott

 

[n8roro]

Tinstar wins. I replaced the thermostat, and flushed the heater core. The heat was about the same. Then I bent the heater door cable and it shut all the way. The heat is much better now. Thanks for all the help.

 

[cucvrus]

I just found this suggestion from another thread:

http://www.autozone.com/cooling-hea...r-core/pro-source-heater-core/459245_0_0_6774

Has anyone tried this one? Or should I just use the spectra premium that has been mentioned in several other threads?

That looks like a good heater core also. I did not see that one. It is nice and should work just fine. I have been using the aluminum ones because that is what they give me when I order one. But that copper / brass looks nice and functional also.