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no heat in 87 Mercury Grand Marquis 100+K


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ttommy2tone
Novice

Nov 2, 2008, 2:40 PM

Post #1 of 13 (6774 views)
post icon no heat in 87 Mercury Grand Marquis 100+K Sign In

No heat in my 87 Mercury Grand Marquis. Coolant full and under pressure, no leaks. Car runs good. Blowers blow cold. I have both automatic and manual switches for temp controls. All control baffles also work which channel heat to defrost, floor, ect. There are all kinds of sensors attached to heater hoses at various places, including one that junctions right before the hose goes into/out from the firewall to the heater core. NOTE I did loose the second fan belt that powered the AC unit (bearings froze up and snapped belt) BUT this NO HEAT condition was like this PRIOR to loosing the belt. The belt powers only the AC compressor and what a mechanic referred to as a "pollution pump". Any suggestions on how to troubleshoot the no heat problem? Thanks! This car is VVG condition and runs/drives sweet so I want to keep it up.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Nov 2, 2008, 8:32 PM

Post #2 of 13 (6760 views)
Re: no heat in 87 Mercury Grand Marquis 100+K Sign In

Hi,

That in line heater hose thing should just be for delaying fan till engine is warmed up for heat request to "floor" only. I'm pretty sure it's just a straight thru heat sensing item - not a check valve but you could by-pass it and just jumper wire the two wires to it so fan works any time requested cold or not.

Follow heat on heater hoses and see if they get cold at some point. Chances are the heater core is plugged a bit and probably would flush out and give you heat again.

Watch out for heater hoses especially if still originals. Clamps are in tough spots to remove and you can break a heater core or the pipe that runs under upper intake manifold so go easy.

Haven't had a duct or diverter door problem with these cars yet so I'm really thinking it's just plugged up heater core itself. Feeling the hoses should be informative,

T



ttommy2tone
Novice

Nov 3, 2008, 7:11 AM

Post #3 of 13 (6752 views)
Re: no heat in 87 Mercury Grand Marquis 100+K Sign In

Thank you Tom. I will flush heater core by trying to break clamp connections at firewall (as opposed to try to flush whole system). I'll re-post results.

Any advice on the broken fan belt that spins the AC condenser? Can I bypass the AC unit if I don't want to mess around with the freon lines and break it down? (Would brobably have to replace AC condeser with a junkyard unit for cost reasons). The only other thing that that belt turns is the "pollution pump". Does that device do anything crucial?


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Nov 3, 2008, 7:22 AM

Post #4 of 13 (6749 views)
Re: no heat in 87 Mercury Grand Marquis 100+K Sign In

Just so you know: The orig clamps you'll probably find at firewall will loosen up and can tap down on the bolt -VERY CAREFULLY then snip the clamp. One hose is easy to replace the return goes under upper intake and that connection is hard to get at AND that tube goes all the way to the front with a small 10mm hose unseen off of it to upper intake. There's a nightmare waiting for you if stuff breaks! Trust me.

If hose connection and hoses look ok at the firewall you may do better to leave them alone and work with the hose connection for heater core at that temp sensor in line and from up front behind A/C bracket - it's easier there and you can flush just the core from those two.

The heater hoses are "moulded" meaning plain hose just won't do for these but the correct ones are available. I can't stress enough for you to do everything to NOT break off the inlet/oulets where hoses go. The "S" hose behind A/C support bracket even from new can rub unseen so if orig - toss that one while system is empty of coolant - in fact if you have a keeper of a car here toss as many as you can at this age.

Bonne chance mon ami, (good luck)

T



ttommy2tone
Novice

Nov 3, 2008, 7:39 AM

Post #5 of 13 (6746 views)
Re: no heat in 87 Mercury Grand Marquis 100+K Sign In

10-4. This is a job I can do with the right advice. I will proceed carefully. I know the value of replacing worn parts BEFORE they go and cause MORE SERIOUS problems and inconvienience. Appreciate the detailed advice. Will post further questions,... results.


ttommy2tone
Novice

Nov 11, 2008, 6:28 AM

Post #6 of 13 (6719 views)
Re: no heat in 87 Mercury Grand Marquis 100+K Sign In

So far I've checked the heat in the hoses. Both hoses into and out of the firewall are hot. If that indicates the core is is not blocked, I don't want to break the connections. This car has an automatic temperature control as well as a manual blower. Could this be an electrical problem where the termostat is not reading right? I have been under tha dash and the diverter doors and blowers are working, but I have not taken the plastic cover off to access the core area. Still no hint of heat at all in car with the engine and hoses hot. Should I try to flush core anyway even with the return hode hot?


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Nov 11, 2008, 7:12 AM

Post #7 of 13 (6717 views)
Re: no heat in 87 Mercury Grand Marquis 100+K Sign In

Not the core if both hoses are hot then hot water gets thru - that test with it running and blower on suggests any heat didn't transfer and came out hot still. A plugged core would be markedly colder coming out when heat requested as any heat would have been removed. Now I'm guessing and I do know this car. Owned an 87 LS - all toys "Spinnaker Blue" - nice car from my Dad back when. He used to complain all the time that the heat or A/C was AFUed but had a pile of papers on the dash blocking the inside air temp sensor which I think is under the dash pad - careful as they are not great vinyl but can remove to inspect up there. I think you'll notice air is constantly going in from dash and up thru a small speaker like vent thru that dash pad - that's where it decides to cool or heat to request.

At this age (I own a bunch still) several things are on the maybe list. Control head itself might not be truly asking for warmer air and ducts are just behaving as told. Truth is I've had so little trouble with the distribution boxes on any in the vinage I have little direct experience! They have been outstandingly dependable! I suspect sensors are dirty. Reveal them and blow compressed air CAREFULLY thru and perhaps backwards too. If you can get your hands on actuators certainly do watch that they react and move to requests. It's a blend door that delivers the mix of heat and fresh air in heat mode I believe and is also sensing it to not be too hot too.

Should just be a bunch of Phillips head screws to take of top of dash pad to take a look there. Again - careful as it will be brittle and small speaker screens may break up so tend to them then or you may be hearing buzzing from debris on the speakers if they are broken while there. I have replaced that with fabric after cleaning those out before.

If the problem is in the control head I really am at a loss as to how to diagnose it except to find the actuator and turn it by hand making the heat come on full temp and chase wiring back to see what's telling it not to??

T



(This post was edited by Tom Greenleaf on Nov 11, 2008, 7:19 AM)


ttommy2tone
Novice

Nov 11, 2008, 7:13 PM

Post #8 of 13 (6705 views)
Re: no heat in 87 Mercury Grand Marquis 100+K Sign In

I removed the dash pad. There is a small elec sensor right in front of the steering wheel directly under what looks like small speaker holes in the dash pad. I am not sure if it was an air temp sensor though) I blew that out with air. Dash was overall clean. Watched actuators employ on vacuum pressure as I slid the control arm. No difference. Still all cold air. Not sure what you mean "control head" or where it would be found on that car.

No luck so far. I think I am getting to the end of my capability. Don't want to take the whole dash apart when I dont know what I'm looking for. Thank you for helping me through step by step. Any other suggestions?


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Nov 11, 2008, 8:03 PM

Post #9 of 13 (6703 views)
Re: no heat in 87 Mercury Grand Marquis 100+K Sign In

Arggh! That little dohicky on dash pad does have to do with sensing interior air temp. What I mean by "control head" is the panel you make the requests at. If it just plain doesn't send the right signal even I would struggle to figure that out. So far ZERO have failed so I'd be guessing like you are now??Crazy That colder thru hotter request is interpreted to make a door move which apparently isn't - - again - can you move one by hand and make it blow hot air?

Ok: Perhaps another here has an idea as to the best next approach for diagnosis of this. I'm pretty dang sure heater core isn't it but if you want to flush thru to make sure so muc the better. I can't really understand how both hoses can be hot if ducts are in fact in right position. You said things were clean in general. The whole core plugged up from the outside seems far fetched. I suppose you could take a look/see thru heater blower and see if there's a mess in there??

Next if I/we can't help here. The folks at ACSOURCE - another site I'm at just do A/C stuff and many are from AZ and in Mexico where lots of these cars still are on the road working hard.

The link below the flag should get you to the forum and it does require sign up but it's slow there now and you'll get quick and excellent attention. They can't post pics easy there but just explain what you have ovserved so far which seems well described to me and see what others think. It's a family owned site but does have lots of techs check in all the time.

Just checked that blower delay valve - happen to have a new boxed one in shop - part #Motorcraft - YG 238 - I looked right thru it and it's not a restriction device as I though - just senses temp and allows fan to work when there's some heat detected. Fan will work anyway on defrost or bi-lev choice. When OE the inlet hose which has that thing in it for these cars with Auto A/C also has a small obstruction put inside the hose. It's like 1/2 of a wine cork tapered at one end and a 1/4" or so hole in it. It's there to slow the hot coolant flow down as the 1/4 hole is plenty. You can feel for it it hose isn't too hard. If it's missing it will still work but you get a rushing sound of coolant in dash sometimes. I know - I mistakingly left that thing out on one of of them for a customer and ended up buying that car and it worked so I never put it back in - still got that car and parting it out for two others right now! Everything works - just rusted out. That happens to be a 89 Town Car - same stuff almost exactly as GM and CVs.

Again: Re-check those heater hoses when running, heat on full heat, full blower. Inlet hose should be hot and outlet that goes to rear of upper intake plenum should be warm to hot if working. If cold return it really can only be restricted, not flowing at all, low on coolant OR IF JUST WARM AND NOT HOT THE DANG AIR SHOULD BE WARM COMING INTO THE CAR proving where the heat went.

I really want to see this fixed for you and me too! If you can think of any other observations we have missed let me/us know. I think I've covered about all I can think of,

Tom



ttommy2tone
Novice

Nov 13, 2008, 10:26 AM

Post #10 of 13 (6686 views)
Re: no heat in 87 Mercury Grand Marquis 100+K Sign In

Tom, I dismantled part of dash and glove box door to expose a large vacuum piston that services the main black plastic housing that houses the duct work around the heater core (i think?). When I started to apply pressure and remove the vacuum hose, it sounded like a door released inside and I immediately got heat.

I couldn't get at this one easily without dismantling the dash around the glove box. I got a better view of what did what. Thank you much for your advice. I got heat. I'll have to see if there is sufficient vacuum source or if the door or accuator are stuck. What and where creates the vacuum tube vacuum source? Thanks again for taking me through this!

Ttommy2tone
North Andover MA


(This post was edited by ttommy2tone on Nov 13, 2008, 11:51 AM)


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Nov 13, 2008, 11:42 AM

Post #11 of 13 (6681 views)
Re: no heat in 87 Mercury Grand Marquis 100+K Sign In

I'll insert replys in CAPS


I wanted to doublecheck the idea of a clogged core, so I disconncted the hose going into the firewall (the one more to the passenger side). It was the hose with the plastic T shaped sensor. I blew even slight pressure into the hose toward the core and coolant rushed out the opposite end (so it seemed completely free of obstruction).

That little dohicky on dash pad does have to do with sensing interior air temp.
Is there any way of jump wiring the sensor to fool the system that it needs heat? That would tell me if the sensor is the problem. If i take out the fuse for the climate control, would it bypass the switch and call for heat? NOT REAL SURE ON THAT. CHECK ANY AND ALL FUSES ANYWAY. IN A CASE I MENTIONED BEFORE THERE WAS A PILE OF PAPER BLOCKING IT WAS THE WHOLE PROBLEM.

I suppose you could take a look/see thru heater blower and see if there's a mess in there??
Do you mean from the outside of the car, the screen in the plasic housing mounted outside the car by the wiper well that goes into the back of the blower motor?
Can I access any mechanical door from there that would open the air channell to pass over the core? BLOWER MOTOR AND SHROUD UNDERHOOD IF REMOVED MIGHT REVEAL A PROBEM??

colder thru hotter request is interpreted to make a door move which apparently isn't - - again - can you move one by hand and make it blow hot air?
I can only see one door on the passenger side against the outside Rt wall above where the right foot would rest. There is an arm connected to a vacuum piston that opens the door to what appears to be the blower on the other side of the firewall. That piston actuator attached to that door does not seem to open that door. When I open it manually (and hold it open) there is still no HOT air coming out of that box. SHOULD BE AT LEAST 3 ACTUALTORS/DOORS - 1- POSITION, BLEND, FRESH OR RECIRC AIR. SOME MIGHT BE SEEN WITH GLOVEBOX REMOVED.

I don't see any other doors under the dash I can access. There are 2 other hard black sealed plastic cases under the dash mounted to the firewall. One is in the middle of the passenger side directly in line wth (I think) the heater core and the blower. The other is directly in the middle (behind area). The vacuum tube activated pistons have an arm that goes directly into the boxes, so I cant open any other doors manually. The arms do move when affected so I am guessing that the arms should be opening the ducts inside. There are some pistons that do not activate, so I tried to manually move those arms to effect the doors inside the box. When I did, I still did not feel heat.

I did find a snap junction of the plastic tubes where 3 (of 8) tubes had melted closing off the vacuum. I thought I had found the problem and cut and repaired the tubes and reattached them. That must have made more of the vacuum pistons move (if my vacuum source is sufficient) but it did not solve my heat problem. FIX ALL THOSE VACUUM/PLASTIC HOSES - THEY COULD BE THE WHOLE PROLBLEM. CAN SPLICE WINDSHIELD WASHER HOSE OVER THE BAD AREAS.

Just checked that blower delay valve - happen to have a new boxed one in shop - part #Motorcraft - YG 238 - I looked right thru it and it's not a restriction device as I though - just senses temp and allows fan to work when there's some heat detected.
Where is that located and how would it effect the no heat condition? Is that the T sensor under the hood that controls the engine fan? BLOWER DELAY IS JUST THAT AND THAT ALONE. IT CAN'T STOP OR CHANGE THE TEMP - IT JUST DISALLOWS BLOWER TILL ENGINE IS WARM AS TO NO BLOW COLD EARLY AT YOU. I ROUTINELY JUMP THAT SO BLOWERS WORK ON REQUEST AND DON'T WAIT FOR FASTER HEAT THAN THE PRESET FOR THOSE. WHEN IT'S ZERO OUT 40F AIR FEELS FINE - I'LL TAKE THAT EARLY!

The more things we rule out, the more determined I get to at least identify the problem (even if not fix it). I still think it is something simply identified if I knew the right sequence of steps to test. I'll try the ACsource site. Thanks again for your help, Tom. I'll post my results. THOSE PLASTIC VAC LINES ARE MY GUESS NOW. I THINK THE ACTUATORS YOU HAVEN'T SEEN YET ARE VACUUM CONTROLLED NOT ELECTRIC MOTORS. I HEAR THEM "HISS" IN MY OWN CHANGING REQUESTS. THEY'RE SMALL BUT COUNT. ALSO THE SOUP CAN WILL MAKE DUCTS DEFAULT TO DEFROST ONLY IF LEAKING. JUST PLUG IT AND IT WORKS BUT DEFAULT WHILE DRIVING IF LEAKING. I HAVE SPARES/REBUILDS OF THOSE.

Ttommy2tone
North Andover MA (just up the road) SEND ME A PM IF YOU WANT AND CALL ME. YOU AREN'T THAT FAR AWAY FROM MARLBOROUGH, MA BUT WE MIGHT GET MORE DONE FASTER JUST OVER THE PHONE. ACSOURCE HAS THE TECHS THAT ARE STILL DEALING WITH THESE MORE OFTEN NOW AS JUNKERS BUT MUST HAVE WORKING A/C IN THE SW + MEXICO - WE NEED THE HEAT JUST AS MUCH! THE CARS LAST LONGER THERE WITHOUT THE RUST BULLCRAP WE HAVE HERE AND THEY DIE FROM THAT BEFORE THESE PROBLEMS CROP UP - HENCE I DON'T SEE THESE TROUBLES BUT HAVE WITH THE PLASTIC VACUUM LINES. GOOD LUCK - CALL IF YOU WISH. I'LL GIVE YOU PREFERRED # BY PM, T



ttommy2tone
Novice

Nov 13, 2008, 11:54 AM

Post #12 of 13 (6678 views)
Re: no heat in 87 Mercury Grand Marquis 100+K Sign In

Tom, I edited my previous post after your reply. Here it is below.

Tom, I dismantled part of dash and glove box door to expose a large vacuum piston that services the main black plastic housing that houses the duct work around the heater core (i think?). When I started to apply pressure and remove the vacuum hose, it sounded like a door released inside and I immediately got heat.

I couldn't get at this one easily without dismantling the dash around the glove box. I got a better view of what did what. Thank you much for your advice. I got heat. I'll have to see if there is sufficient vacuum source or if the door or accuator are stuck. What and where creates the vacuum tube vacuum source? Thanks again for taking me through this!

Ttommy2tone
North Andover MA


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Nov 13, 2008, 1:29 PM

Post #13 of 13 (6676 views)
Re: no heat in 87 Mercury Grand Marquis 100+K Sign In

WAY GREAT TO HEAR TOMMY! Take note of what you touched that was stuck. Those doors should have a pretty strong "home" position to be changed by vacuum motor/actuator. As I said before these are VERY dependable and I've worked on these exact ones since forever and never had this type of fault as a feather in my cap to tell exactly what would be the trouble. NS - I own three right now with the same heater/distribution box - all work and all have had same faults. Owned a few more before the ones now too and worked on dozens - most all just the same routine issues.

The doors that should look like choke plates to fit inside the distribution box should have either felted (like window rubber) or plain rubber ends and I suppose could jam up.

Just fun and for notes on these cars in general that seems common to all in the rust belts:

*That soup can will rust at attaching thing on bottom but can be fixed. First you notice upon accelleration or heavy load that all ducts go to defrost.

*The control panel will act up on the plain "floor" setting. If you nudge the request just a tad towards bi-level the fan will operate on auto mode for another 100,000 miles! Common issue.

*The inline delay is plain stupid IMO. I just jump that with wire and tie the plug to the silver A/C return line from black accumulator and leave it. One I'm restoring to near new so I bought the stupid temp delay thing to make it original - still in box - that's why I had the part #. I actually hate ATC in cars - just let me blast heat or air full blast and adjust the fan myself thankyou! I hate it in Winter when there's 2 feet of snow and an inch of ice under it all over car and windows and you run them for an hour to clear off to move and the damn climate control is happy inside at 80F when you want all you can get to clear the car off and it's slow because of the ATC.

* Trans support bars give out at frame ends. If not broken now spray grease all over them as when they break the trans will drop down and fan on engine will hit fan shroud underhood and scare the crap out of you! Hard to get that bar used - call me if you need one.

* Door lock motor are special too. If they fail in open or lock mode some will prevent manual override - another great idea from FORD! I keep those in stock and make up the rods as needed for fronts, rears, left and rights as needed.

* If you have the trunk pulldown feature and use the trunk a lot........... Disconnect battery, open trunk when closed and unplug the thing in its down position. When those fail they fail UP and your luggage gets wet! Cute!

* A/C - They must be already done but the springlock O rings all fail. You should be on 134a by now - an easy convertion. Shaft seal on OE compressor will leak over Winter on cars stored outdoors and show no evidence when checked and charged up in Spring - call me!

* Glove box lock. Right now go out and spray the two tabs with WD-40. When they break just one will pull in and you have to remove glove box by the hinge to open it. That latch I have and they are getting hard to find. If the car is nice you still keep the color of vinyl with a used replacement. They only made a few key types for those and you can get lucky and OE key will still work.

* Heater hose "s" type thing behind brackets for A/C compressor will rub if OE - toss it now. Must remove plate but not that hard to do. The one on rear to under upper intake manifold is a b*tch! It goes to a metal hose that will rust out so spray the rest of your WD-40 all under there now. There's a 10mm hose off of it you can't see or fix without removing the upper manifold that goes over to throttle plate where you see it.

* Fuel pum relays. They are under plastic cover on driver's inner fender on plate with 8mm little bolts. You can get it out by just bending it up. Have a universal spare with you - they go like a bulb and you walk. It's the one with the green skirt on the relay/plug.

* Spray aerosol grease all over the rear spring lands on differential. Those rust such that you need a replacement rear end! Spray all fuel and brake lines. One hidden behind driver's plastic inner fender skirt will rust out and empty your gas tank for you - nice FORD safety feature! Guess the Pinto guys were still at it!

* Chrome on shifter, directional lever will peel and is sharper than a surgeon's scaple! Just peel it all off or wrap it. They can be replaced if you care.

* Front brake calipers use a rubber thing that will allow whole caliper to rattle badly. Whole rebuilt caliper is under $20 bucks so don't bother replacing just those.

* Put on right angle grease fittings on inner tie rod ends. You can't grease them with steering in certain positions if you don't point them down and you know the quickie shops don't steer the car to do them. Do grease the pitman arm lots. They really do wear out!

*Seal at downward shaft of steering box is common. Problem solved is slow now with Trans-X - last ions if you catch it.

**** tons more easy quirks on these.
___________________-

Ok - I just bashed FORD for some not so "Better Ideas" in these cars but face it - they give a huge car ride and sip fuel for the size of them. Trunk can hold 1/2 dozen dead bodies with no problem with room for luggage!

Many routine items are easy and inexpensive on this vintage. Exhaust is VERY reasonable as are all brake parts.

___________

I'm retired but kept two of this body for keepers and one for parts as the New England bone yards have squished most all of them now for the metal. Same basic drivetrain whether a Crown Vic, Grand Marquis, or Town Car which is just 4" longer in back seat and interior more of a pain but are chiefly the same cars.

Good luck. Hit me/us up with any future issues with this. Chances are I've "been there, done that" already with these - except this diverter door you just went thru!

T







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