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little to no heat...Intake leak?

5K views 24 replies 12 participants last post by  oxyg3ne 
#1 ·
I have been dealing with a lack of heat issue for a while. I finally broke down and took van to the shop ( one i am familiar with and trust). originally took it in to have water pump replaced as i have heard and read here that the impelars can rust off and cause littel flw through system causing heat to suffer. that would have been better. upon inspection mechanic says I have an Intake leak. could this loss of pressure in the system lead to barely luke warm heat at best? anyone ever heard or dealt with this?
 
#3 ·
ok I guess i should post all the attemps i have made to get heat. all started over a year ago. I replaced the heater core which was leaking. at that point i had perfect heat for about 2-3 months. then all of a sudden..cold air. replaced thermostat..warm air for two weeks then cool...replaced heat control valve... heat for about 2 weeks then cool. replaced radiator cap (figured maybe a pressure issue) no change. replaced blend door actuator...heat for a day..then cool. "burped" system multiple times would get heat for about a week or less. pulled heater core to check for blockage..there was none. re-installed and "burped" system.. heat for a day or 2 then cool. flushed system, refilled..heat for a day or 2 then cool. at some point i actually changed the control module in the dash too, no change. finally gave in and took it to a trusted mechanic. He said possibly the impellers on the water pump were rotted off and not moving fluid throught the system like it should...that was not the case but when he had it apart we found significant stainng and leaking at the intake gasket....he replaced that gasket and i picked it up yesterday. I had heat for aout 5 minutes now it is cold. arrrghhhhhh.. wtf?
 
#4 ·
Hose from water pump to heater core. Water returns to intake.

Are hoses hot when heat is on? Is flow being blocked there?

There is a selector door that has a gear that likes to go out. LeAnn has posted this part taken apart. It would block the hot air from actually reaching the cabin.
 
#6 ·
I am about to change my heater core due to low/no heat. I can get some heat when I rev the engine. A few days ago I pulled the lines of the heater core (from the engine compartment) and blew our the core. Lots or crappy water came out. I had good heat for two days. Now i have no heat.
 
#7 ·
Changed the heater core. Wow, that was easy.

Still only good heat when I rev the motor or drive.

Doesn't seem like much water flowing from water pump.

The fact the heat is correlated to engine speed make me rule out the air vent door. (For now)

Water pump not moving enough water?

Blender/bypass stuck? But increase rpm means less vacuum (typically) and actuator would stay closed even easier. If I am correct the actuator bypasses the heater core when AC is on and vacuum is applied to actuator. Just a 4-way valve.

I still hear water pouring through the heater core from inside the cab which to me indicated an air lock. I pulled the upper heater core hose off and stuck a vacuum cleaner to a piece of 5/8" heater hose and took off the rad cap and put some air from the air hose. Not sealed or under any kind of pressure and tried to burp the air out of the heater core. No real success.

Like I said, ok when driving but not idling.

Cheers
 
#8 ·
If you rev the motor and get heat, then your vacuum lines could be switched. There should be no vacuum supplied to the heater valve inline with the heater core hoses. That only gets vacuum from the dash, which turns OFF the heat for A/C. If there is always vacuum, then the valve opens a little when you rev the engine as vacuum changes. I learned that the hard way with my van after messing with the lines, and the guy that did the V8 swap before I bought the van had them screwed up as well. Of the two locations coming FROM the firewall, the lower hose is only connected to the heater valve. The upper hose is what supplies vacuum to the switch panel and the vacuum ball reservoir.
 
#9 ·
Definitely sounds like a vacuum line issue. Bad vacuum line, leak, etc.

Since the heater control valve was replaced, make sure that the correct line and fitting was hooked into the vacuum port on it. Do not glue the fitting into place. Doing so will result in glue getting into the valve.

Also check for small cracks in any elbows or vacuum fittings. All of these things can affect your heat. Best bet is to locate the correct vacuum line diagram for your van and go through each line and fitting one at a time.
 
#12 ·
The Drummer said:
Mine as the bottom hose burming hot ,but the top one remains cold ,little warm at best , still as bit of heat ,but far from normal , what is it ?.
That sounds like the core is clogged OR it's cold in the cab and the heater is doing it's job, sucking all the heat out of the core and putting into the van.

Lump
 
#14 ·
What nobody mentions so far is that the out flow fitting from the engine to the heater hose is restricted so the engines radiator gets most of the flow for hot climates. That is why when you race the engine the heat gets hotter because the heater hose is getting more water and it doesn't have time to cool off. The heater rad core has the exact opposite job of the engine rad so you want the water going thru it fast so it doesn't lose as much heat in the process whilst the engine rad needs the water going thru slower so the passing air has time to cool it. Drill out the engine to heater hose fitting larger or go to Auto-Zone etc where they will have them with different size holes.
 
#15 ·
@DRZ, I can see what you mean about a restriction in the line but I couldn't see it being a design flaw because this system used to blow nice hot air. Something has changed.

I have now changed the $80 vacuum controlled heater bypass control valve. The one that allows water to bypass the heater core during A/C.

NO CHANGE.

I still have barely any heat even with the engine revving.

Hoses at the heater core are: one warm and one cooler. I know one should be HOT and one a bit cooler.

I am believing now that either:

1. the new heater core is plugged from transient debris in the system,

2. the water pump is failing by not providing enough pressure differential across the heater core lines to cause water to flow,

3. the outlet or inlet line has an obstruction that is only overcome when the engine RPM is up (more pump flow --> more pressure differential)

There appears to be no vacuum problems.

I am now going to research which way the lines to the heater core flow. Either from the manifold thru the HC then to the WP or from the WP thru the HC then to the manifold. I am pretty sure its out of the manifold thru the heater core and then to the water pump but I read what appeared to be an experienced poster saying otherwise.

Cheers all.
 
#16 ·
In my case i blew the heater core with garden hose both ways and air both ways , went from about 132 degrees C in the dash vents to over 165 C ,never saw much crap comming outa there at all but it fixed it allright ,heater valve had been disconected and vacuum hose pluged with a screw , heater valve still working fine ,probly was unhooked cause of the lack of heat .
 
#17 ·
check for low coolant. this is exactly a textbook case of what low coolant level does, and everything appears to work right otherwise. also the system may appear full, sometimes the level is difficult to get right due to air in the system. i've battled this many times.
 
#19 ·
SOLVED!

Good news and bad news.

Good news is I now have LOTS of heat.

Bad news is it was a b$##h to fix. Yours may be easier.

If you look at my other post you'll see that I had already reversed flushed my old heater core and then proceeded changed out the heater core (EASY!) and got a bit heat for a few days then only so so. Then I was only getting SOME heat if the motor was revving up. Then nothing.

I was going to change the water pump as I thought there wasn't enough flow through the heater core.

I did not 'drill out' the fitting on the manifold as DRZ suggested above as it had decent heat before. So design issues weren't at the top of my list. It did get me thinking though.

So what's the solution? ENGINE BLOCK FLUSH

DRZ was on the right track with thinking there was an obstruction but it was debris preventing good flow through the heater core, not a design flaw. The debris was in the engine, not the heater core.

I did the following:

1. cut the lower rad hose in half and remove THERMOSTAT
2. attach a 1hp pump and tank to the cut lines (in series)
3. refill with water and drain again
4. refill with water, CLR, and Oxalic acid (wood bleach)
5. flush for 4 hours. (my pump/tank combo had a reversing option too)
6. drain and fill with water
7. flush for 10 minutes
8. drain and fill with water and WASHING SODA to neutralize the acid
9. drain and fill with water
10. flush for 5 minutes
11. drain and fill with water and 1L TSP (TriSodiumPhosphate)
12. flush for 1 hour.
13. drain and refill
14. flush
15. replace rad hose and thermostat
16. fill with 50/50 DI water and antifreeze (no dexcool).
17. enjoy your heat
 
#21 ·
I have a co-worker with the dexcool constipation in a Jimmy. I want to grab a sample of that crap and try the TSP on it. I'll bet that is all you really needed. He said he used the flush in a can before so I wonder how effective that stuff really is.
My new motor got the green, in a pinch you can add almost anything and not worry that you'll make sludge in the block.
Once, towing home my '70 Ford high top camper van with my Nova, '78 inline six overheated. Jeez, wonder why? Think the sportster in the back of the van was too much?
We poured our last six pack into it and the few six packs we drank prior recycled of course and made it home.
I did have Jiffy Lube do a flush afterward, gave the guy in the pit a $20 tip when he was done.
 
#22 ·
I put a sock on the return to the tank and captured a small handful of booger sized green globs with a soft plastic feel to them.

Remember the TSP is a separate rinse/washing agent than the acids mentioned. If you do do the acid wash then remember to neutralize with the washing powder.
 
#23 ·
zeusdog said:
I did the following:

1. cut the lower rad hose in half and remove THERMOSTAT
2. attach a 1hp pump and tank to the cut lines (in series)
3. refill with water and drain again
4. refill with water, CLR, and Oxalic acid (wood bleach)
5. flush for 4 hours. (my pump/tank combo had a reversing option too)
6. drain and fill with water
7. flush for 10 minutes
8. drain and fill with water and WASHING SODA to neutralize the acid
9. drain and fill with water
10. flush for 5 minutes
11. drain and fill with water and 1L TSP (TriSodiumPhosphate)
12. flush for 1 hour.
13. drain and refill
14. flush
15. replace rad hose and thermostat
16. fill with 50/50 DI water and antifreeze (no dexcool).
17. enjoy your heat
Dude!

Way to go on the monster flush! ... :rockon:

Lump
 
#24 ·
I suppose any future responses to no heat or random heat issues should be first asked....green coolant or dex cool. If switched from Dex, then it's a question of how it was flushed. I got a set of rear heat controls from a member here, and while they were functional, I had to clean out a weird residue out of them. I can only assume a dried version of a dex/green antifreeze reaction. It looked like a fluff of debris. It was easy enough to clean out, but I can just imagine that dex/green mixed is like having plaque build up in your arteries.

I good block flush is certainly the way to go. I pulled frost plugs out of my old 89 high top's 350 and flushed with the garden hose and was blowing out what looked like sand in the lower part of the block. A cleaned out cooling system on an old van will do wonders.
 
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