[Unknown User]

All of a sudden the defrost/heater isn't working on my 78 280Z. It blows warm/hot air only in city driving(less than 50mph)at highway driving (more than 55mph)it blows in outside air or cold air. My A/C compressor belt is removed. All vacumm lines are connected. No major work has been done in relation to this system. Water temp is at normal operating range. I am puzzled!!! Thanks in advance.

 

[Unknown User]

> All of a sudden the defrost/heater isn't
> working on my 78 280Z. It blows warm/hot air
> only in city driving(less than 50mph)at
> highway driving (more than 55mph)it blows in
> outside air or cold air. My A/C compressor
> belt is removed. All vacumm lines are
> connected. No major work has been done in
> relation to this system. Water temp is at
> normal operating range. I am puzzled!!!
> Thanks in advance.
Try checking the vacuum line ends for cracks,
we have fixed many 78's by clipping the cracked
ends off and reattaching them. Joe

 

[Phantom]

> Try checking the vacuum line ends for
> cracks,
> we have fixed many 78's by clipping the
> cracked
> ends off and reattaching them. Joe

EXCPO,
Concur with Joe. It definitely sounds like a vacuum leak. In addition to hose ends check the nipple fittings at your vacuum accumulator bottle on the passenger side fender well. Frequently the nipples on the bottle will crack & leak. Best way to determine if you have a leak is to crank the negine and listen for the hiss. Start under your dash where ther engine noise will be somewhat muted. If the engine is too noisy for underhood investigation - turn the engine off while you are standing somewhat over the open engine bay. If you hear a short hiss right after you turn it off - you have a leak somewhere and need to get someone to help you look for it. One listens while the other starts & stops motor. You can also get a can of sspray starter fluid - you know - the stuff you used to spray in carburators to get a car to start. If you let your engine idle and then do following.
1) Spary starter fluid onone hvacuum hose connection and then wait 15 seconds. If nothing happends - great. If the engine speeds up just a little bit - you have a vacuum leak at that point. do spray just a little at each point - soak it! This is how I finally found my leaks.
Hope this helps,
Phantom

 

[Phantom]

> Try checking the vacuum line ends for
> cracks,
> we have fixed many 78's by clipping the
> cracked
> ends off and reattaching them. Joe

EXCPO,
Concur with Joe. It definitely sounds like a vacuum leak. In addition to hose ends check the nipple fittings at your vacuum accumulator bottle on the passenger side fender well. Frequently the nipples on the bottle will crack & leak. Best way to determine if you have a leak is to crank the negine and listen for the hiss. Start under your dash where ther engine noise will be somewhat muted. If the engine is too noisy for underhood investigation - turn the engine off while you are standing somewhat over the open engine bay. If you hear a short hiss right after you turn it off - you have a leak somewhere and need to get someone to help you look for it. One listens while the other starts & stops motor. You can also get a can of sspray starter fluid - you know - the stuff you used to spray in carburators to get a car to start. If you let your engine idle and then do following.
1) Spary starter fluid onone hvacuum hose connection and then wait 15 seconds. If nothing happends - great. If the engine speeds up just a little bit - you have a vacuum leak at that point. don't spray just a little at each point - soak it! This is how I finally found my leaks.
Hope this helps,
Phantom

 

[Doug Dawson]

> EXCPO,
> Concur with Joe. It definitely sounds like a
> vacuum leak. In addition to hose ends check
> the nipple fittings at your vacuum
> accumulator bottle on the passenger side
> fender well. Frequently the nipples on the
> bottle will crack & leak. Best way to
> determine if you have a leak is to crank the
> negine and listen for the hiss. Start under
> your dash where ther engine noise will be
> somewhat muted. If the engine is too noisy
> for underhood investigation - turn the
> engine off while you are standing somewhat
> over the open engine bay. If you hear a
> short hiss right after you turn it off - you
> have a leak somewhere and need to get
> someone to help you look for it. One listens
> while the other starts & stops motor.
> You can also get a can of sspray starter
> fluid - you know - the stuff you used to
> spray in carburators to get a car to start.
> If you let your engine idle and then do
> following.
> 1) Spary starter fluid onone hvacuum hose
> connection and then wait 15 seconds. If
> nothing happends - great. If the engine
> speeds up just a little bit - you have a
> vacuum leak at that point. do spray just a
> little at each point - soak it! This is how
> I finally found my leaks.
> Hope this helps,
> Phantom

Alternatively, you could just replace every hose in your engine compartment -- something I think you should definitely do once every 15 or 20 years.

Doug Dawson
[email protected]

 

[Phantom]

Spoilsport!!

> Alternatively, you could just replace every
> hose in your engine compartment -- something
> I think you should definitely do once every
> 15 or 20 years.

> Doug Dawson
> [email protected]

But Doug - It's so much more fun to chase those phantom leaks every year or so!!!!!!

 

[Unknown User]

This won't tell you what's wrong, though...ctxt...

Doug Dawson wrote:

> Alternatively, you could just replace every
> hose in your engine compartment -- something
> I think you should definitely do once every
> 15 or 20 years.

While the basic premise of replacing worn hoses (vacuum or fluid) in a timely manner is sound, actually DOING so in your case may prevent you from ever finding out exactly WHAT CAUSED YOUR HEAT/AC PROBLEM, unless........

.........you replace one vacuum component at a time (i.e. vacuum hose, vacuum tank, vacuum actuators, etc) at a time, and THEN see if that fixed your problem. If it didn't, then replace ANOTHER vacuum component and see if THAT fixed your problem....etc, etc, etc.

The final choice is, of course, up to you.

Regards,
Sammy in CT

 

[Doug Dawson]

Re: That's not really the point, though.

> While the basic premise of replacing worn
> hoses (vacuum or fluid) in a timely manner
> is sound, actually DOING so in your case may
> prevent you from ever finding out exactly
> WHAT CAUSED YOUR HEAT/AC PROBLEM,
> unless........

> .........you replace one vacuum component at
> a time (i.e. vacuum hose, vacuum tank,
> vacuum actuators, etc) at a time, and THEN
> see if that fixed your problem. If it
> didn't, then replace ANOTHER vacuum
> component and see if THAT fixed your
> problem....etc, etc, etc.

The thing here is not necessarily to find out which hose might have been causing a problem. After 15+ years in the field, _all_ of your vacuum etc. hoses will have substantially deteriorated. They should all be replaced. ( And also the coolant hoses, and PARTICULARLY the fuel hoses. ) This is independent of any troubles you may or may not be having.

IF after you've replaced the hoses, the trouble goes away, that's really great, and you can just forget about debugging the system. OTOH, if there is STILL a trouble, then you've totally eliminated a major potential cause of it, and can instead focus on possible hardware problems. This is always good diagnostic practise, to narrow down the potential causes ( really, really cheaply. )

FWIW, vacuum hoses are so very inexpensive that I can't imagine anyone having a problem with simply replacing them as routine maintenance on the car. Do it! It's good for you!

Doug Dawson
[email protected]

 

[Doug Dawson]

Re: That's not really the point, though.

> FWIW, vacuum hoses are so very inexpensive
> that I can't imagine anyone having a problem
> with simply replacing them as routine
> maintenance on the car. Do it! It's good for
> you!

I should point out that I'm bitterly opposed to replacing things left and right just for the **** of it when you experience a malfunction. I think this is bad diagnostic practise, and can turn out to be ridiculously expensive ( and often futile. ) HOWEVER, this does not apply to standard maintenance items which should periodically be replaced etc. whether or not you are experiencing a problem, such as PCV valves, filters, and so forth. I strongly believe that after a period like 15+ years, your car's hoses fall into this basic maintenance category. It would IMO be irresponsible not to perform this basic maintenance procedure of replacing before looking at other causes.

Doug Dawson
[email protected]

 

[Phantom]

Acronym Dictionary?????

> I should point out that I'm bitterly opposed
> to replacing things left and right just for
> the **** of it when you experience a
> malfunction. I think this is bad diagnostic
> practise, and can turn out to be
> ridiculously expensive ( and often futile. )
> HOWEVER, this does not apply to standard
> maintenance items which should periodically
> be replaced etc. whether or not you are
> experiencing a problem, such as PCV valves,
> filters, and so forth. I strongly believe
> that after a period like 15+ years, your
> car's hoses fall into this basic maintenance
> category. It would IMO be irresponsible not
> to perform this basic maintenance procedure
> of replacing before looking at other causes.

> Doug Dawson
> [email protected]

Doug,
Any more acronyms? Maybe we need a file for them too? My 20 years of Naval service came in handy on your lalst two postings. I actually figured them out.
BTW - I agree with your replacement, test policy wholeheartedly.
Phantom

 

[Doug Dawson]

Re: Acronym Dictionary?????

> Doug,
> Any more acronyms?

Acronyms?

You mean, FWIW, IMO, BTW, or do you mean PCV?

FWIW, PCV is pretty standard, and most people know what it means even though they don't have any idea what it stands for. :^)

I come originally from Usenet ( the newsgroups on the Internet, that some may have heard of, ) so all the other acronyms are so elemental that they're covered in the FAQ that all new users of Usenet must read. Heck, it's really basic electronic media stuff. I wasn't consciously aware that some people might not know it, if they've already mastered the Web and stuff ( where these things also appear all the time. )

FWIW == For What It's Worth
BTW == By The Way
IMO == In My Opinion
FAQ == Frequently Asked Question(s)
PCV == Political Correctness Valve

> Maybe we need a file for
> them too?

I guess people can look them up in the Archive now! :^)

Best regards,

Doug Dawson
[email protected]

 

[Doug Dawson]

Re: Acronym Dictionary?????

> FWIW == For What It's Worth
> BTW == By The Way
> IMO == In My Opinion
> FAQ == Frequently Asked Question(s)
> PCV == Political Correctness Valve

OOOPS! I forgot one!

OTOH == On The Other Hand
OOOPS == Oh! Oh!! Oh!!! P*ss! Sh*t!!

Doug Dawson
[email protected]

 

[Phantom]

How 'bout FUBAR & SNAFU?

> OOOPS! I forgot one!

> OTOH == On The Other Hand
> OOOPS == Oh! Oh!! Oh!!! P*ss! Sh*t!!

> Doug Dawson
> [email protected]

Thanks for the education Doug. I didn't know what FAQ meant and, silly me, I thought PCV stood for Positive Crankcase Ventillation. Seeing your definition, I'm certain yours is more appropriate.

Have a great New Years!
Phantom

 

[motorhead]

C'mon guys, I'm lost!!

> Thanks for the education Doug. I didn't know
> what FAQ meant and, silly me, I thought PCV
> stood for Positive Crankcase Ventillation.
> Seeing your definition, I'm certain yours is
> more appropriate.

> Have a great New Years!
> Phantom

Just figured out what BFD is, now your adding code. Could we all speak English for the sake of us novices?

 

[Phantom]

Your handle would be Mtrhd

> Just figured out what BFD is, now your
> adding code. Could we all speak English for
> the sake of us novices?

Just trying to help out with your acronym knowledge. Have a great New Years!!!
Phantom

 

[motorhead]

How 'bout Mthd = Meathead See!! I'm learning!

> Just trying to help out with your acronym
> knowledge. Have a great New Years!!!
> Phantom