Cabin Heat slow to warm up

[DennisG01]

Just curious if I've got a problem, or if everything seems normal. It seems like the cabin heat is taking longer to heat up as of recently, but I've really just started to pay attention to it as it hasn't been too cold until lately.

The water temp gauge seems to climb at the normal rate, eventually reaching between 180 and 195, depending on if I'm sitting still, going slow or at higher speeds (and higher RPM's). Although, maybe it's climbing a little slower than normal, not positive.

Other than a blockage in the cabin's heat exchanger, any ideas? It does eventually blow nice and warm, but will cool if the RPM's slow down.

I flushed the cooling system twice over the summer, which is why I'm wondering about other possibilities. I realize a blockage could still be the problem, but am curious about other things.

[JohnC]

Try bleeding the cooling system. If it has an air bubble the heater can blow cold even when the engine is warm.

If you find air, the next thing to do is figure how how it got there....

[DennisG01]

Good idea, and easy enough to do. Thanks, John. I will do that... but... would an air bubble work it's way out ? I ask because the "slow to heat" is pretty stable, meaning the same thing every morning. Takes a while to get warm, then only stays warm with increased rev's. It doesn't turn "cold", but it does get noticeably cooler as I see the water temp gauge dip down to the 185* mark, or a bit below (when in stop and go traffic, or idling, for example).

[leolkfrm]

parking it with the nose up hill might help burp it!...heard it has worked on some

[DennisG01]

I loosened the bleed screw on the t-stat housing with the engine running and a solid stream of AF squirted out. I did it a few more times and kept getting a solid stream.

I also visually verified that the "recirc" door is operating. Although, I figured it was as I can hear a noticeable change in the air/blowing sound when it press "recirc".

??? I think I might clamp off the rear heat lines in the engine bay. That should at least eliminate a variable, right? But, the rear is another problem. I've never had good (well... decent, anyways) heat coming out until traveling at highway speeds. I've flushed that system as well.

[DennisG01]

I clamped the rear heat supply/return lines. No change in heat performance of the front heat. It still only gets somewhat warm, but not until I'm traveling at consistently higher RPM's (highway speeds). Once I slow down, there is a noticeable drop in warmth. It does not get "cold", but I would refer to it as lukewarm, at best. I'll take my IR gun with me and jot down some actual numbers.

I would really be surprised if there was a blockage in the front heater core, since when I flushed it this summer, water seemed to flow through it very easily. But, could it be anything else?

[DmaxMaverick]

Thermostat. If it isn't closing (or is missing), the pressure differential may not be enough to force much coolant through the core.

Verify the return line isn't blocked. If coolant can't get out of the core, it can't get in, either.

Is the hose routing original? Was the pump replaced at some point before/during the problem?


Try removing the heater hoses and route them to a container. Idle the engine for a few seconds at a cold start and actually see where flow is going. You should see significantly more flow from the supply than the return. If equal, there won't be much, if any, flow through the core.

[DennisG01]

OK - I can do that.

Concerning the T-stat issue... does that still hold true since I have 2 stats? If it matters, the temps I see on the dash gauge are where I have always seen them (ie, they have not changed since this problem started). My ScanguageII gives a water temp readout that will vary between about 183* to 190*, once the engine is warmed up.

I replaced the water pump when I put in the Schoolcraft engine, about 3 years ago.

Although they have been off an on a few times, the heater hoses are still plumbed the same way they have been since I got the truck at 60K miles (about 125K, now).

http://www.thedieselpageforums.com/photopost/data/519/medium/5044.jpg

[DmaxMaverick]

If it worked last winter, and you haven't (intentionally/knowingly) changed anything, then something has changed you don't know about. External changes are fairly obvious. Internal changes not so much, but happen over time.

Dual stats are no different than single in operation, other than having one more. At any rate, they should be closed until the coolant temp nears their rated opening temp. They weaken over time, and tend to either begin opening too soon, fail to open smoothly, or don't open at all.

Without something jumping out and taking the blame, effective diagnosis involves breaking down the system by function, and testing each function. Usually starting at the functions with easiest access and the least effort. Restriction is easy to test and see without special tools. Only time and effort is required. Start there. If it checks out, I suggest replacing the thermostats (even though your temps seem to be normal). Use Robert Shaw OEM spec stats. John Kennedy can help with this (he has them, and I can't find them anywhere else that I trust).

[DennisG01]

Thanks, will do. I can't remember off hand how old the stats are (but they are Shaws from Kennedy). I'm thinking I probably replaced them when I did the engine.

I'll check on the restrictions and post back. Might take a few days... until this cold front passes. It got down to 6* last night. Only about 19* right now - should be in the mid-40's by the weekend.

[DmaxMaverick]

Just had a thought.......

Maybe an easy test for the stats and flow function...... Start cold, then shut down as soon as you see the coolant temp begin to rise (before it's warm enough the stats should begin to open, but enough you should have vent heat). Clamp/pinch the upper radiator hose. I use a large pair of channel lock handles and a zip tie to hold them closed. If they don't pinch closed enough, you can slip sections of PVC pipe over the handles. Start and watch the coolant temp, and monitor the heater output. If it's remarkably improved, you can bet the stats aren't closing enough when cold.

Also, if you are using any selection of "defog", or "recirc", the A/C compressor will engage, creating a colder air situation. This "feature" is intended to do 2 things: help dry the air in the cabin, which reduces internal fogging; and "maintains" the A/C system when it wouldn't normally be in use (circulates the oil, rather than letting it pool for months). This is normally a good feature, but will also reduce the effectiveness of the heat available to the core.

[rustyk]

I couldn't see where you mentioned the rear heat - whether or not it's normal.

If not, you may have an arrangement like my Ford van; there's a solenoid valve to the heater core supply (from the 'stat). It cuts off water flow to the heater cores when the A/C is on max.

If this is sticking, it could be the source of the issue.

[DennisG01]

I couldn't see where you mentioned the rear heat - whether or not it's normal.

If not, you may have an arrangement like my Ford van; there's a solenoid valve to the heater core supply (from the 'stat). It cuts off water flow to the heater cores when the A/C is on max.

If this is sticking, it could be the source of the issue.

Thanks, Rusty. I don't think there is one - at least not to my knowledge, but I could be wrong. The rear heat has been a problem for years. I just figure the system isn't balancing (flow) properly to get adequate flow to the rear. The front has always been good, though, up until recently. Now they are both problematic.

[DennisG01]

Just had a thought.......

Maybe an easy test for the stats and flow function...... Start cold, then shut down as soon as you see the coolant temp begin to rise (before it's warm enough the stats should begin to open, but enough you should have vent heat). Clamp/pinch the upper radiator hose. I use a large pair of channel lock handles and a zip tie to hold them closed. If they don't pinch closed enough, you can slip sections of PVC pipe over the handles. Start and watch the coolant temp, and monitor the heater output. If it's remarkably improved, you can bet the stats aren't closing enough when cold.

Also, if you are using any selection of "defog", or "recirc", the A/C compressor will engage, creating a colder air situation. This "feature" is intended to do 2 things: help dry the air in the cabin, which reduces internal fogging; and "maintains" the A/C system when it wouldn't normally be in use (circulates the oil, rather than letting it pool for months). This is normally a good feature, but will also reduce the effectiveness of the heat available to the core.

If I understand correctly... clamping the hose will keep the coolant from circulating (or at least not entering the radiator)? OK - that's easy enough to try.

I have been using the recirc button since the air blows out harder. I experimented with the button (on and off) on the way to work today. I didn't notice much, if any, difference - at least by using the back of my hand as the temp sensor, anyways.

[DmaxMaverick]

Yes. Clamping the hose will simulate closed thermostats. If there is no difference, then they were already closed.

Selecting "recirc" is the same as selecting "Max A/C". It circulates air from inside the cabin, through the HVAC stack, with only a little outside fresh air mixed in. You should have noticed occasional A/C compressor cycling with it selected. This is also why there is more air blowing from the vents. However, if the air isn't being heated, more volume isn't helping any.

With the engine up to operating temp and idling, feel the heater hoses. If they're hot, then the problem isn't flow. The problem will be with the temp gate/servo not fully diverting the through the heater core. A lot of this isn't making sense, and I think this is what it will lead to.

If it were a front/rear balance problem, one or the other should be getting hot, not neither. The rear may have a separate issue.

There is no flow control solenoid in your system. Coolant flow to the heater core(s) is continuous, or supposed to be, anyway. Older Ford heater coolant flow systems were either mechanical (push-pull) or electric.

[DennisG01]

The problem will be with the temp gate/servo not fully diverting the through the heater core.

I did play around with the temperature selector dial yesterday, wondering the same thing you are stating. I moved the dial to about 4 or 5 different positions (from full hot to full cold) and I was able to feel a difference in the temperature at each position. However, maybe I'm not actually getting a full swing from cold to hot (0% heat to 100% heat, for lack of a better term)? Maybe the door isn't completing it's movement so I'm only getting 0% to 75%.

I'll be able to check on the other stuff tomorrow evening.

[Robyn]

The Blend door servo motors on these have been known to take a poop.

Under hard running the heat output from the core is sufficient to give "WARM" air but at idle or lower speeds the heat will fall off.

This is due to the air blend door motor not moving the door properly.

The recirc door motor is a BITCH to get to and IIRC you almost have to remove the HVAC unit to do so.

Now the recirc door is not really needed for heat or AC, just used mostly during HOT weather to get the max cooling from the system.

The Blend door servo I believe is accessable.

There is a special sequence for setting these things too.

The HVAC system I believe is tied in with the computer ??????
If you can gain access or see under the dash, move the heat control from cold to hot and watch whats happening.

The servos are a little black box. There are three of them, one for the blend door, one for the mode (defrost, heat, etc) and one for the recirc

If you can access the servo motor, remove it so you can see what its doing and then run the thing to see if it makes its full sweep.

These little servo motors have plastic gears and can/do wear out.

The way they work is fairly simple, when they reach the end points the motor runs against the stops and then the amp draw increases and the electronioc controls senses this and shut off the power. Then when the selector is moved back to say the mid point, the controller allows the motor to move the door a predetermined distance to approximate the heat level desired.

When the selctor is moved to the opposite end say cold from hot the process reverses and the motor will run aqainst the stops and shut off.

The doors can bind due to crud finding its way in through the cowl vents and or plastic parts wearing out.

If you can get the servo off the shaft, you may be able to manually move the door shaft/door and see if the issue is the servo or the door itself.

If you can move the door manually and get HOT air then the issue is far easier.

My guess is that the issue is either the Dash controller or the servo motor.

My first hunch is that the servo has/is dieing.

Now depending oon whatcha find, the dash may have to be loosened, lifted and or removed :( to gain access.

IIRC the blend door servo is accessable (sort of)

Good luck and keep us posted

[Robyn]

OK

Dug out my 94 service manual and took a peek.

The HVAC system should be very similar.

The servo's (actuators) are located as follows

The temperature/defrost servo is loacted on the end of the HVAC case close to the throttle pedal. It will have a small bundle of wores pluged into it.

The Mode servo (acutuator) is located on the front of the HVAC case in about the middle between the drives right foot and the RH side of HVAC case.

The recirc servo is on the far RH end IIRC (could not find reference to it in the book right off)

You should be able to watch the servo on the LH end (defrost/temp) and see what its doing.

Missy

[Robyn]

I"M BACK

Here is a link to a well put together You tube video on this very subject.

http://www.youtube.com/watch?v=Ow0OOfIFtlU

This gives a fairly good idea of whats up and where stuff is.

Good luck

Missy

[DennisG01]

Thank you, Robyn! I can certainly check on that. Is the blend door the same thing as the "temp/defrost" door? I assume yes, just wanted to double check.

[QUOTE=Robyn;287303] It will have a small bundle of wores pluged into it.

ummmm... Is that "o" supposed to be an "i", or did you forget an "h"?;)

[DennisG01]

Oops. Should of watched that video before asking that question. That video was GREAT! Thanks for that link, Missy!

[Robyn]

Hope it all comes out OK without major surgery on the HVAC unit.

Keep us in the loop.

Missy

[DennisG01]

I clamped the large hose that goes to the radiator. I didn't see any difference in the speed that the engine warmed up. It seemed about the same. Tomorrow, I'll check the flow into a bucket.

Next, I took the glove box out. The servo is in the middle of this picture -- white label with black barcode. Very hard to get to - looks like I might be able to get to it easier by removing the power (cigarette lighter) receptacles, though.

http://www.thedieselpageforums.com/photopost/data/519/medium/photo_1.JPG

I was able to see the post move with the help of a mirror. I enhanced the picture the best I could to make the metal post easier to see. It appears to swing through about a 60* swing. It moves with every little click of the temp selector knob.


http://www.thedieselpageforums.com/photopost/data/500/medium/Cold_Position.jpg


http://www.thedieselpageforums.com/photopost/data/500/medium/Warm_Position.jpg

[DennisG01]

I think we're getting closer!!! Can I assume there might be some type of blockage in the coolant crossover or the hose between the crossover and the "T" connector?

I know that fitting on the crossover is supposed to a "quick connect", but but I've read stories of how it is also a "quick break" connection. Mine is only a few years old, though. How do I get it off? I didn't want to to start forcing that piece as there is plastic there.

Please don't laugh at my "contraption"... or at least don't do it too loud! :rolleyes:

This is idle RPM, cold engine (maybe 80*-100* coolant temp). Barely a weak, little 1/8" stream (probably not even fair to call it a "stream")

http://www.thedieselpageforums.com/photopost/data/519/medium/photo_11.JPG



This one is 1350RPM, approx same temperature coolant. This yielded a "rough" stream - not solid, still small diameter.

http://www.thedieselpageforums.com/photopost/data/519/medium/photo_2.JPG

[Robyn]

The little coupler on the Xover (RH side) has a restrictor orifice in it, and this could have issues.

Getting the aluminum pipe out requires that you retract the little lips on the plastic insert and slide the pipe out.

Now, you are already up to speed on these things, yesss they break off in the xover and are a bitch to get out.

If you do break it off, DO NOT despair, the Xover can be salvaged easily.

You simply remove thye Xover get it out where you can see what your doing, then using a die grinder relieve the aluminum from the inside of the coupler on opposite sides (make a little groove the length of the coupler part thats broke off)

Once you have a little groove on opposite sides that just starts to show the threads of the Xover port your good.

Now you take a small capeing chisel and small hammer and peal the offending part inward and away from the threads in the Xover.

This may seem like a tough task, but I can usually manage to extricate these within 15 minutes or so once the Xover is off and on the bench.

Once the broken part is out, run a Pipe tape (1/2") through the threads to just clean it out.

Install the steel version of the coupler from NAPA or ??? parts house and your good to go.

Smear some Hi Temp RTV on the threads before installing the new coupler.

Good luck and keep us posted

Missy

[DennisG01]

Thanks, Missy. Now that you mention it, I remember taking the advice of this forum a few years ago and the one I bought (the one currently in there) is the steel version from NAPA.

Just to be sure -- to remove the Al line from the QD fitting -- just push the plastic "ears" into the fitting and pull the Al line out?

[Robyn]

Yup, Thats the ticket.

The factory "pot metal" connectors were a mess once they had been in there a few years.

I noticed that your rig has the RED coolant.

If this stuff has ever had any other stuff mixed with it it can cause the stuff to plug up the heater cores and such.

Is that a possibility ??

Missy

[DennisG01]

No - it's always had the cool-aid in it. I've thought about changing it to the green stuff, but I've always been worried about what you're referring to. Plus, when I flushed it, it wasn't too bad. It wasn't as bright as it is now, but it was OK.

[DennisG01]

Oh... I should add some info about my little contraption, in case anyone reading this (now or in the future) needs to do something similar and is not completely sure how to do it (as I originally was).

I used 1/2" garden hose (with 1/2" barbed connectors) to extend the factory heater lines, after first removing them from the "T" connector (I have rear heat). If you don't have rear heat, I'm not sure if you'll have any connector at all.

I used what I had lying around for the bottle - it's an apple juice container - it's got decently stiff sidewalls. The heater hose that would normally go to the core is plumbed to the TOP of the bottle. I simply drilled holes (use a step drill bit) in the cap and the sidewall.

Then, use 1/2" barb to pipe connectors. The connector screws in nice and tight to the cap (don't drill the hole to big the first time - experiment in gradual steps). For the sidewall, I first placed an 0-ring on the 1/2" pipe threads to help seal against the container's sidewall. It sealed "OK", but some AF still dripped out - not enough to worry about, though.

I drained about a gallon of AF out the drain plug on the bottom, port side of the radiator before starting this little project. Then, I put it back in through overflow tank before starting the engine. Years ago, I used Kennedy's tip (from his website) of making an access hole through the metal support (that is right underneath the drain plug). Sooooo much easier!

[Robyn]

10-4 on making an access hole.

I cut a rat hole in the inner fender on DaHooooley to allow accessing the drain cock in the radiator too.

The engineers had their head buried a mile on that one. They give you a drain cock, but no way to get to it without tearing the shroud off first. :(

Missy

[DennisG01]

In the immortal words of Bo & Luke Duke.... Yeeee Haaawww!!!!

After years of having no rear heat and chalking it up to "well, it's an old system", we now have rear heat, as well! I was hoping for that - as soon as I saw the flow problem, things started clicking... the weight of the rear heat system (amount of fluid) is substantially more than the front. So, of course, as any fluid does, it takes the path of least resistance.

It was almost a "free" repair. After only a few years, though, that little plastic retaining clip (in the QD fitting) just about exploded in my fingers. So, I just unscrewed to whole thing (QD and metal/rubber line) and took it into the work bench. Fished out the remaining pieces of plastic. Got a new Dorman QD fitting from Autozone ($13).


This is the first thing I saw when I took things apart. I was actually a little frightened... it was a bit dark outside so when I took off the QD fitting, all I saw were these two little "tentacles" waving at me! Yikes! :eek:
http://www.thedieselpageforums.com/photopost/data/519/medium/photo_12.JPG


Golly, do you think this might have accounted for the no-heat problem???:rolleyes: They were all wrapped around the little crossbar in the restrictor.
http://www.thedieselpageforums.com/photopost/data/519/medium/photo_21.JPG



Guys (and of course gal!) - thanks so much! I couldn't have done it without 'yall (still keeping with the Duke theme, there).

And just because I feel so good right now... Yeeeeeeeee Haaaaawwwwww!!!!!!!!!

[DmaxMaverick]

That's great. It's always nice when we have a "Eureka" moment (or a Yee Haw). Looks like someone was a little long on the WP sealant.

[DennisG01]

Looks like someone was a little long on the WP sealant.

I was wondering where it may have came from. Is the water pump the most likely source? Could it have come from somewhere else?

[Robyn]

Whats the track record on the rig??? as in are you the original owner ??


That RTV had to come from somewhere.

Very few places that it could have been used.
Water pump install
Timing cover possibly been off and gooped up upon reinstall
Water crossover

Thats a lot of goop in such long strings.

Would be interesting to know where that came from.

Sure a lot better than having to yank the heater core out. :eek:

Glad all is well.

Missy

[DennisG01]

Sure a lot better than having to yank the heater core out. :eek:


Yeah, buddy!!!!

The engine was rebuilt about 3 or 4 years ago by Ronnie. But, I bought a new water pump while waiting for the rebuild and had the shop doing the R&R put it on.

[DmaxMaverick]

It's from the water pump install, short of someone just putting the junk in. Crossover, timing cover and other parts would have left much smaller pieces, or wouldn't have been in contact with the coolant (or shouldn't have been). Quite typical, actually. I was hoping to hear it wasn't RJ responsible for that (he knows better).

Using a sealant for WP installation is recommended, but no more should be used than is necessary, which equates to a very thin layer of "glue" on the gasket (same with or without a gasket for the crossover and timing cover). Thick beads will lead to your result. The stuff has to go somewhere.

I suggest a back-flush of both heater cores and the radiator. What you took out is only the stuff that got stuck there.

[DennisG01]

I suggest a back-flush of both heater cores and the radiator. What you took out is only the stuff that got stuck there.

I back flushed it twice this summer (maybe last summer?), so HOPEFULLY it's mostly out. I'll see how things go this winter and give it another flush in the Spring before I start trailering. Probably take a look a look at the stats, as well, just to make sure nothing is caught in there.

[Robyn]

When I do a buildup or an install on a water pump/timing cover, I use the good Felpro gaskets that come with the kits and apply a very thin film of RTV to the gaskets to stick them and keep them sealed, plus allow easy removal later if need be.

The much goop is just waaaaaaaaaaaaaaaaaaaaay too much.

Somebody was in a hurry and did not want to go get the gaskets is what it looks like.


Missy