coolant fog coming from dash vents

apaustin

Veteran Member
Joined
Dec 9, 2010
Location
maryland
TDI
05 passat wagon, 96 B4V, 95 glx v6/96 tdi conversion, 97 b4v
I know I could find an answer if I just spent a half hour or so on the search but, I was on a test drive after deleting the resonator on my '96 and unrelatedly, coolant fog started coming from the dash vents and the inside of the windshield started getting scuzzy. With the temp knob all the way to cool, the problem diminished.
As I recall, the heater core remove/replace is second only to having your shoulder rebuilt. I also recall it may be a hose problem - they easier to access?
It's winter and I really don't want to do a major tear-down.
 

0die

Veteran Member
Joined
Nov 29, 2012
Location
corpus christi, tx
TDI
1996 Passat wagon B4V
Pretty sure pulling the core is a PITA...my old rabbit was a pain...I ended up cutting it out from the side and then sealing to box after putting the new one in...the B4 is a bit more complex :(
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
cracked heater core 100%
The hoses are on the outside in the hood area, not in the dash. I highly sugest you not buy an aftermarket or OEM plastic core. There are a few aftermarket ALL aluminum ones that work awesome.
For now you can bypass it but you will have no heat, it will get you around with out having to get stranded on the side of the road.
you have to pull the dash out.
10 hour job if you have done it before.
 

ToddA1

Top Post Dawg
Joined
Aug 3, 2011
Location
NJ 08002
TDI
'96 B4V, '97 B4 (sold), '97 Jetta (scrapped)
Hoses are accessible from the bay side of the firewall.

I’m curious why the fog is lessened with the temp set to “cool”. There isn’t a valve that controls coolant flow... more of a blend box.

I suppose you could disconnect the hoses, flush clean water through mock up some fittings, then see if it holds air pressure.

I did one on the wagon, and it wasn’t difficult, just labor intensive. I guess it’s a plus, if you need to fix the lack of foam on your flaps.

-Todd
 

hey_allen

Veteran Member
Joined
Nov 25, 2006
Location
Altus, OK
TDI
2000 Jetta TDI
I would guess that the reduced fog is just due to the air not going through the heater box, but that the leaking coolant is still coming out, just condensing on the box and puddling/dripping down under the dash.
 

apaustin

Veteran Member
Joined
Dec 9, 2010
Location
maryland
TDI
05 passat wagon, 96 B4V, 95 glx v6/96 tdi conversion, 97 b4v
Without knowing the finer workings of the heater core, I don't suppose it's possible to run the car with the temp dial set on coolest. It could be the summer car and I could kick the 12 hour repair down the road. If a coolant puddle on the floor is inevitable, hmmm, I'm not sure what I'll do. My bride says I have too many b4v's.
 

iluvmydiesels

Veteran Member
Joined
Nov 21, 2015
Location
phila area
TDI
AHU
coolant smells 'sweet', and is sweet and dangerous to animals, however if the evaporators drain is plugged you ll get the (seemingly) same *type of puddle on the passengers side. as its winter, i dont suppose that a/c is out of the question, just my 2cents. if it smells 'sweet', core replacement.
 

ToddA1

Top Post Dawg
Joined
Aug 3, 2011
Location
NJ 08002
TDI
'96 B4V, '97 B4 (sold), '97 Jetta (scrapped)
The dial set to cool, isn’t going to do anything for you.

-Todd
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
Honestly, bypass it if you’re going to drive. You DO NOT want to have this go critical leakage on the road; you will overheat the engine in no time and possibly warp the head. Trust me, I did. It was actually kind of scary when it went kaboom. You could not even see your hand in front of your face in the car and antifreeze mist all over your clothing, face, arms, lips, eyes etc. TDI's can take a bit more abuse on heat than other engines but this goes past the limit that the head can handle. Trust me, by pass it with some plumbing copper parts if you’re in a pinch and must drive it, then again its way to cold out to drive a car with no heat, I had to do that for 1 winter, was not fun.

No matter what setting you have the climate control at, the heater core is receiving coolant from the pump 100% of the time, well in the mk3 they do, most cars have a valve for the heat but it still will not stop all the coolant flow as its just one side of the plumbing, coolant pressure works in both ways, in and out houses from the heater core. You will have a failure eventually. My best friend d has a Euro Van and it always smells sweet when you put the heat on but no fog, no nothing. We took it apart to find some wetness on the aluminum fins; it was evidently nicked when installed from the factory.
 

Vince Waldon

Top Post Dawg
Joined
Apr 25, 2009
Location
Edmonton AB Canada
TDI
2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
My notes/hints/tips on MK3 heater core replacement:

http://vincewaldon.com/index.php?option=com_content&task=view&id=32&Itemid=28

Bargain with the devil all you want... there's no way around replacing it. :) :)

Take your time, put stuff in labeled baggies... not that bad a job. Just time-consuming.

Pretty sure they hung the heater core on the assembly line and then bolted the rest of the car to it. :D
 

Windex

Top Post Dawg
Joined
Apr 1, 2006
Location
Cambridge
TDI
05 B5V 01E FRF
As above, the heater core replacement on the B4V is not thaaaaat... bad, just time consuming.

Hardest part for me was getting the rearmost clips (2) between the heater case and the evap case back in place. I elected to separate the cases and leave the A/C untouched.

It can be done.
 

Steve Addy

Top Post Dawg
Joined
Aug 7, 2002
Location
Iowa
TDI
97 Mk3
As above, the heater core replacement on the B4V is not thaaaaat... bad, just time consuming.

Hardest part for me was getting the rearmost clips (2) between the heater case and the evap case back in place. I elected to separate the cases and leave the A/C untouched.

It can be done.
I agree, I think if you detach the AC pipe hold downs at the strut tower you will have enough room and flexibility to pull the case back enough to get to the two backside case clips.

It's not as clean or nice as being able to take out the whole thing, nor does it allow you to clean the evaporator but it also allows you to do the core without having to discharge the AC.

Steve
 

iluvmydiesels

Veteran Member
Joined
Nov 21, 2015
Location
phila area
TDI
AHU
^really good point that will save you a whole 'other area' of work. and if you get a/c properly cared for at a shop, ie discharge, probably need a flush, if flushed dont you like need to disassemble all a/c junctions, new seals, possibly an oil check, at the least vacuum system on junctions reassembly, possible recharge, and if the shop does all this work, quite a bill, just for a/c, and possibly not as reliable of work. a shop isnt going to spend a whole lot of time on each a/c step. you ll get it back as they feel/spend time, to do.
 

ToddA1

Top Post Dawg
Joined
Aug 3, 2011
Location
NJ 08002
TDI
'96 B4V, '97 B4 (sold), '97 Jetta (scrapped)
I left the evaporator box alone when I changed my core. A rinse free evaporator cleaner can be used, if needed.

-Todd
 
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