Prudence, my 87 Town Car

[gadget73]

probably hanging on the shift linkage. Can't really think of anything else that might bind up.

[Lutrova]

Finally managed to get a second set of hands to help with the mounts. One of the guys from the motor pool came out Saturday afternoon and together we got the job done. I returned the first set of mounts I bought and picked up a pair from a different manufacturer. They were better in the thread department, though the inner holes on both needed to be tapped out. Unfortunately, while tapping the passenger mount the tack welds holding the nut to the mount failed, so we had to reinstall the stock mount. I'm not having great luck with mounts, it seems. Still, it was the driver's side mount that was shot, and that's the one we managed to replace, so at least the primary mission was accomplished.

As for the engine hanging on something, that's still a mystery. We didn't encounter any of the frame groans I had heard last time, even with the engine jacked up as far as it would go. When it came time to lower the engine back onto the mounts, the driver's side seated perfectly, while the passenger's side was maybe 3/4" too far back for the bracket to straddle the mount. It took the two of us pulling on the intake to get the engine to move forward and fall into place. Not something I would've attempted myself, but it got the job done.

I looked at the shift linkage at various points in the process. It doesn't quite look like everything's square and as it came from the factory, but I can't say whether it's always been that way or if things shifted during this job. The car still shifts into the gears I want it to, though, so if it is screwed up it doesn't seem to affect anything.

Overall, this wasn't terrible, but as always the hang ups came from unexpected places. The 13mm swivel socket made getting to all of the bolts a non-issue. I'm sure picking it up before saved me all sorts of trouble. What caught me by surprise was the quality control issues on the replacement mount threads. Tapping/chasing every thread before installing seems like the prudent move. Every other problem I ran into came down to a lack of experience, specifically knowing when it's okay to muscle things.

[87gtVIC]

Good deal.

I was not impressed with the aftermarket mount options either. Life goes on.

[Lutrova]

Been driving the car around post lately and noticed a bit of a squeal when the AC is first turned on. I took a look under the hood with the engine running and there's a distinct ticking sound coming from the compressor's general area that goes away once the AC's turned off. This leads me to believe the AC compressor might be on its way out, but I don't know whether there are any intermediate steps I can take or if replacement is coming up.

Not wanting to tempt fate, my wife and I drove down to Barstow this evening without AC. We also ran without vent air as that seems to be partially running past the heater core. And naturally, the outside air came with gale force winds, because that's just how the Mojave is. At any rate, I had given some attention to the HVAC vacuum lines and connections last summer, but things have never really been satisfactory. It seems that any sort of acceleration or incline is enough to pump out hot air. Obviously something, or multiple things, are amiss. Short of replacing sections and stumbling upon the issue, I think the way to go would be to get a vacuum gauge, see which parts aren't holding vacuum, and work down until the culprit is isolated.

I believe there's a check valve that should prevent any leaks outside the HVAC system from depleting its vacuum? Or at least until the vacuum reservoir has been emptied? I know I have an open line leading to one of the smog pump valves, but that seems like it's too distant in the whole vacuum system to have such a strong effect on the HVAC operation.

[87GrandMarq]

Where is a check valve on the small hose behind the intake manifold. I don’t have a picture but it’s easy to spot, it should be black and white. One line will split off towards the vacuum tree and one towards the vacuum reservoir.


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[gadget73]

The other common problems are the soup can and the thermal blower lockout. Not impossible for things inside the dash to be leaky too, but most of the time its the stuff under the hood that causes more trouble.

[Mainemantom]

Another thing that I found to be a problem (cracked) is the vacuum tree in the engine bay near the fire wall. Mine was white plastic multi ports. Hard to find a replacement. Vacuum lines could be cracked there too.

[Lutrova]

I took a look earlier today and saw that I had already replaced the check valve and soup can. The TBL had been removed and vacuum lines capped off, too. So I think I've addressed all the low hanging fruit. If it's the vacuum tree then, as you say, I may have a problem finding a replacement.

I ordered a vacuum pump with gauge off Amazon to assist with diagnosing the leak. It should get here on Monday. Meanwhile, I've been thinking about my one known leak, which I believe is the line running to the thermactor air bypass valve. One the one hand, if the smog pump is dumping air when not at idle, then maybe this one spot is sapping all my vacuum. On the other hand, it looks like there should be a check valve in between the bypass and manifold - unless that's broken too. On the third hand, it's 2 am and I don't really know what I'm talking about.

Anyway, I'll reattach what I can tomorrow and hopefully know more definitively on Monday.

[gadget73]

the check valve should make that a non-issue if its actually checking. Any leaks on the engine side of the vac tree won't affect the climate control under load unless its not actually sealing correctly. I'd verify that works, seen a lot of people circle around these exact problems only to come back to the newer check valve not actually sealing.

[Lutrova]

My vacuum pump/tester came today. I took the entire dash apart trying to get at everything vacuum related. Turns out, all I ultimately needed to do was unhook the glove box, pull the lower dash cover, and remove the radio and mounting plate. Right behind the radio is the 'Harness Vacuum Connection Block', which made testing for vacuum in both directions easy.

First, I tested at the vacuum check valve off the vacuum tree. The check valve was leaking, so I swapped it out with the original, which also leaked, but very slowly. In fact, it might not leak at all, but my testing method is to hold my thumb over one port, pump vacuum on the other, and see if it holds with the checked port open. From there I checked the two lines coming off the valve. The line leading to the vacuum reservoir - which I've swapped with a plastic Aero TC part - holds steady. The other line going through the firewall will build vacuum, but loses it fairly quickly.

Next, I disconnected the HVCB and checked for vacuum in both directions. Eight lines run through this block, coming from the back of the HVAC panel on the dash and going to all the motors and sensors and such. I lost my notes for all the lines running into the HVAC panel, but all the holding and losing of vacuum for each line seemed to correspond with the EVTM, at least as I understood it. Testing from the HVCB going out, however, turned out some leads. Six lines held vacuum, but the black/purple line was completely open, while the black line would build a little vacuum and then leak moderately. The black/purple line goes to the Vacuum Diverter Valve, which might be behaving normally.

Finally, I disconnected the two lines going up to the blue temperature sensor and again tested in both directions. The clear line going into the temperature servo held vacuum, as did the black line going back to the rest of the system. In the opposite direction, both clear and black lines running into the temp sensor either held no vacuum or had a significant leak. The leak persisted even when I held my thumb over the open line I wasn't testing, and at both ends of the temperature range on the HVAC panel.

So the check valve might be leaking very slightly, but my working theory right now is that the automatic temperature sensor has a pretty significant vacuum leak that causes the entire system to lose vacuum and default to full hot under lighter loads than it should.

If that theory is correct, then maybe I could fix it by either clamping off or somehow plugging the black line going to the temp sensor. Though I guess that would starve the temp servo and leave me with full heat. Perhaps the solution then is to unplug the temp sensor lines and 'short' the black supply line to the clear servo line, which should provide fully cooled air. As I'm typing this all out, it occurs to me that the auto temp sensor is supposedly just a variable vacuum leak. But if it fails in the full cold position, there shouldn't be hardly any vacuum escaping, while in my car it seems like the majority of vacuum is. The final piece of the puzzle that I still don't understand is the Vacuum Diverter Valve. It appears to play some part in the temperature selection, but exactly how it relates to vacuum I'm not sure.

[Lutrova]

Update: I bypassed the temp sensor and ran a line directly from the black supply line to the clear servo line. Wasn't pretty but it took care of my vacuum leak. I went on a short test drive and so far the results are promising. Kept cool vent air all the way up a long hill where I would usually switch over to heat. I won't have full results, though, until this weekend when my wife and I leave post and drive through the mountains on our way to LA.

Knowing now that the temp sensor is leaking so badly, I wonder if the same buildup preventing a good seal is also keeping it from adjusting with the temperature. Based on Hillbillycat's promising results, I guess I'll be picking up an ultrasonic cleaner and seeing if I can clean things up any.

When the temp sensor is working properly, does it modulate vacuum to the servo by blocking the line off or by venting vacuum to the cabin? I would hope the former, but I wouldn't be too surprised if it was the latter.

[Hillbillycat]

My sensor is in the car now, but right now I have a no-start issue (read other thread), so I wasn´t able to check the function.

[gadget73]

The vac diverter valve is what operates the outside air / recirc door when things are full cold so you get max AC performance. It lives on top of the HVAC box, next to the gold vac servo. Not sure how visible it is, but you can just cap the line off that feeds it if you want. Its a really shitty valve, basically just a plastic tube with a rod inside that is pushed by a wire. I think its got an O ring seal. Basically it blocks the port off when the blend door is not at full cold. Try blocking the two hoses off that go to it and see if the system works that way. if it does, the air temp sensor is OK and its just that valve that has failed. You can connect the hoses together and force it to be in recirc mode any time you have the AC on.

[Lutrova]

I poked around with the gold servo but I don't think I can really get at the diverter valve without pulling the servo. Which might not be too difficult, but I think for now the point is moot. My wife and I drove down to Huntington Beach for the weekend and the air stayed cold for the whole ride. So I'm thinking the diverter valve is probably fine and with the temp sensor bypassed I'm currently (more or less) leak free.

I'd still like to figure out a long term solution for the HVAC that restores some function, but that's probably a discussion for Hillbillycat's thread.

The latest nonsense is some pretty strong but maybe intermittent vibrations. They seem to occur regardless of speed. I couldn't tell whether they went away by shifting into neutral. It's also become a little more difficult to turn, which doesn't seem to be a power steering fluid level issue. I thought I could feel some sort of vibration over the past month, but it really become noticeable today. Last time I attempted to address this issue I was working on the motor mount theory. And since replacing one the idle vibrations seem to have gone. But perhaps there were two sources. Gadget's other suggestion was a bad u joint, and some light googling this evening seems to jive with the latest symptoms.

Since we're on the road I can't really do much investigation. But I had already made an appointment with a nearby differential shop for Monday. I was hoping they could address, or at least diagnose, my acceleration whine. But they ought to be able to investigate the vibration, too. If it is a bad u joint then that's probably not too bad. If it isn't, then it's coming from one of the wheels?

[Arquemann]

If it isn't, then it's coming from one of the wheels?

I have a tire that's gone bad and it has quite a bit of runout. Tire guy wondered how I'm even able to drive over 50mph, even though the vibration is actually very minor. I guess it's just the combination of a lot of sidewall plus soft suspension. Weirdest part is that the vibrations most likely caused by it don't appear every time. Depending on the road surface, the vibrations can appear at higher or lower speeds even, and might disappear when cornering...

How "sharp" is the vibration on yours?