1983 Continental Vacuum Issues & Follow Up

Hi Bill,
Let me start by saying that I have a 1983 Lincoln Continental Base Sedan. The car has about 70,000 miles and hasn’t been driven much in the last 20 years. Recently I replaced the heater core/ac evap core myself, and then took the vehicle to my mechanic to have a complete tune up done. They charged the AC system, replaced valve cover gaskets (they were leaking pretty bad), spark plug wires, new cap and rotor, etc… The car runs beautifully but we are stumped on one issue. When the car is idling the HVAC system works great. Air blows cold when set to AC, and Heat blows hot when set to heat. You can also move between defrost, panel, and floor vents accordingly. The issue is that when you start driving the car, or put the engine under a load vacuum seems to drop and heat just starts blowing out of the defrost vents and floor vents. My mechanic has replaced a host of vacuum lines and check valves in the dash and under the hood, but to no avail the problem keeps happening. They have tested the vacuum canister for leaks also. After speaking with him today he has deduced that the engine is no longer creating enough vacuum due to stuck rings. Could this be possible? The car runs excellent, and is very drivable at this point in the process. I’m having them check into adding an external vacuum pump if possible? I don’t see it necessary to tear down my engine at this point. What would your thoughts be on this issue?
Thanks,
Tyler
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Hello Tyler –
Your symptoms are classic undiagnosed loss of vacuum issues within the confines of the ac/heat vacuum control system. For us at Lincoln Land the problem is always corrected when the leak is diagnosed and corrected. We have never heard of an engine being worn out to a point that it cannot produce sufficient vacuum to operate the accessories properly. Such an engine would display other problems such as poor performance, hard starting and heavy oil consumption etc. Still, if your mechanic is a professional and believes this theory he will prove to you and himself that your engine is indeed in this worn out condition by doing the usual specific engine diagnostic tests for this problem such as complete cylinder compression testing. It would be interesting to see a copy of the vacuum diagram that he used to check out the vacuum leak in the ac/heat controls in your 1983 Lincoln.
Sincerely,
Bill
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Bill,
I reiterated your email to my mechanic. He got back at it and found two vacuum leaks. Everything works spectacular now. I just have one more question for you. The vehicle runs great, but at idle when the A/C compressor kicks on, it seems to put a heavier than normal load on the engine and causes the engine to stall at times. The compressor is charged with the correct amount of refrigerant and oil, but the clutches seem to be making almost like a continuous loud clicking noise when the compressor is running. Would you recommend replacing the clutch/pulley assembly, or the whole compressor?
Thanks,
Tyler
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Tyler –
We are glad for you that finally the correct diagnosis and repair corrected your a/c control problem. It is nice to hear that you talked your mechanic into revisiting the vacuum situation for your a/c controls before overhauling your engine. Wouldn’t it have been awkward if you paid big dollars for an engine overhaul only to have the same a/c problem. What would the mechanic say at that point.
With regard to your new problem, I cannot begin to answer a refrigeration question of this type without knowing the following information. I would need to know the amount in pounds of refrigerant that was charged into the system, the type of refrigerant used along with any other additives, the high side and low side pressures at an engine idle and also at a high idle and finally the ambient temperature during this test. From your description, the system sounds as if it is under severe stress from some unknown malady that I can’t begin to identify without this further information.
Sincerely,
Bill