This one'll stump you all.......

[burn_your_money]

Is your coolant level a little low? That'll kill the heat.

[ORCoaster]

B_Y_M  thanks for the reminder that mine is short in the reservoir and causes the gauge at the flange to read a bit low.  How did you know?

[R.O.R-2.0]

B_Y_M  thanks for the reminder that mine is short in the reservoir and causes the gauge at the flange to read a bit low.  How did you know?

after you log soo many miles in a mk1. you kinda have a mental connection to the car.. you know the cars every move, and whats right.. and any little change!

[rabbitman]

Wow, thanks for all the replys!!

I do have the radiator almost completely blocked. But like 8V said, I don't think it helps other than to keep the cold air off the engine itself.

T-stat is "I think" a 195F. I just had a 87C in there and swapped it out for the slightly hotter one.

The cold air side vents are blocked off at the heater box, I never had the ducts to carry the air to the vents, I think the PO lost 'em.

Coolant level is good.

My electical system is ok, sometimes I see a difference in the gauge that I can't account for but it's usually short lived and then goes back to normal.

Water pump is for sure good. The skinny return hose is always squirting even at idle and then really hard revved up......haven't checked this pump with the screwdriver jamming method though.

-50F is not very nice to the poor car, I have all the engine heaters so it's actually easy to start but turning the steering wheel is difficult and if you thought the MK1 body rattled bad you should hear one that's really cold......no suspension at all.

I also have an electric after run water pump off a '95 passat in the feed line to the heater core. It helps a lot at idle and a little bit revved up.

I've changed heater cores 3 times and have always really checked the foam seal around it and it's always been good. Last winter I installed a VEMO brand heater core and it was pretty good until this winter.

I flushed the system a year or two ago and it was clean.

I'll update as I think of more stuff.

[AudiVWguy]

OK, so what do you think about removing the valve that controls the heat so you get max flow through the heater core. Should be easy and quick and lose hardly any coolant in the process.

[8v-of-fury]

Honestly, I do not think that is the problem. Any of the gas mk1 vw's dont have any issue with heat. and they use the exact same valve.. its just that the motor is literally making no heat and it being that cold its probably struggling to maintain optimum combustion temperatures too.. lol

[ORCoaster]

I just finished changing out the blower motor on my 81.  High speed was ok but the lower two were squealing to beat the band.  Out did the music most times.  What I noticed between the two heater cores I was working with is that they both had stuff piled up on them.  I live around a lot of trees and all kinds of needles, leaves and stuff was coating part of my heater core.  The blower motor was not really bound up, more of a wear issue at the bearing but it really couldn't force are down through the heater core to the rest of the plastic housing.  I put in a motor from a car that had air conditioning and it really pushes the air now. 

What are the chances that something is inside the blower motor squirrel cage?  You should be able to see in there from outside the car under the rain tray.  Anything plastered in there that would reduce air flow?  Does it spin up good?

[burn_your_money]

B_Y_M  thanks for the reminder that mine is short in the reservoir and causes the gauge at the flange to read a bit low.  How did you know?

Because my mom's is low 
 PM sent

[rabbitman]

OK, so what do you think about removing the valve that controls the heat so you get max flow through the heater core. Should be easy and quick and lose hardly any coolant in the process.

I did that a few years ago and it didn't fix anything and then earlier this year I looked through the valve and it was totally clear so I didn't think it was worth leaving it out.

8V, my engine does get completely hot, it just takes a while.

ORcoaster, I had the heater core out a year ago so I doubt it would have blockage so soon, it also blows hard.

And to throw another wrench into it. I also have an auxilary heater with the coolant routed in series, first through the stock heater and then through the aux heater..........as soon as the temp needle starts to move the aux heater is blowing "heated" air, by the time the engine is up to temp the air is HOT. Yet the stock heater is only a little warm.

So in summary: The engine does get to operating temp, the stock heater does remove heat from the cooling system, the aux heater blows hot air, but the stock heater is somehow losing the heated air or getting cold air into the system.

I feel like I've overlooked something for the last 5 years and I'm dyin' to find what it is.......I really don't want to throw money at another heater core.......

The fact that the aux heater works so good really has me confused.

[R.O.R-2.0]

your problems are INSIDE the box.. there isnt foam somewhere that foam needs to be..

[ORCoaster]

On the heater box I was working with this weekend there was a layer of foam at the joint where it connects to the hole in the rain tray, between the motor and the box and then there is foam all around all sides of the heater core.  When I pulled the core out to check it for ability to hold water under pressure I noted foam on the sides of it, and it was totally mush.  I could see that cold air could draft past the heater core as it is the path of least resistance.  Foam also on the end where it goes into the box on the end opposite the hoses.  If that foam was gone missing air would flow there as well.  I am not sure the heat from the core can go any other place than out the bottom of the box. 

I agree you need some foam somewhere. 

[rabbitman]

Maybe I have to look it over again.

A couple years ago I reached in the hole where the fan mounts and put duct tape around the outside of the heater core, it didn't help at all.

I also had some heater cores that I could shine a light in the inlet and see light in the outlet.........so that meant the coolant was allowed to shortcut and NOT go to the end and back. That was when I got the vemo core and it mostly fixed it for one winter.

Maybe a mouse got in there and chewed the foam out...........

[ORCoaster]

Wouldn't be the first time.  I have heard tales or tails where nests were built on top of those cores and when the new owner turned on the heat they started smelling all that nasty stuff and couldn't figure out what it was. 

[somolovitch3]

You said the cores are in serries, wich one is first? Have you tried them in parallel? Where is the aux core located in the car?

[rabbitman]

You said the cores are in serries, wich one is first? Have you tried them in parallel? Where is the aux core located in the car?

The stock heater comes first so it can have the hottest coolant available going through it. I did try running them parallel and it didn't seem to be much different than series.



Wasn't too bad last night at -25F but this morning at -45F the air coming in was warmer than -45 but wasn't warm enough to be called heat.....