1998 plymouth voyager heater problem - no heat

I bought this van about a month ago and now the heater just broke on
me. Its a 3.0 litre, 3spd, A/C, airbags, no other options.

Last time I was in the van the heater worked fine. Got in it today and
turned on the heater and after a few minutes I could tell something
was wrong. Now it just blows cold air. The fan works normall, all the
speeds are there. Usually the heater is cranking out heat after only a
few minutes of driving.

I'm not as familiar with the van as I should be. The heater mode dial
has always worked kind of funny, very smooth, it doesn't click on the
different modes which I think is kind of peculiar but I don't know.
None of the modes appear to work now either. I try each mode, pause
between modes to give it time to switch, but there is no change in
where the air is directed, ie windshield, feet etc. All the modes
worked the last time I was in the van.

I haven't checked the fuses yet as I don't know which one controls the
heater. I checked the manual but it still wasn't obvious. There's no
trouble shooting guide with the manual either.

Any help would be greatly appreciated.

 

Check for bubbles in the coolant. The 3.0 is good for blown head gaskets and
in some conditions will allow exhaust into the coolant casing air locks.
Bleed your cooling system and see if the problem clears up. If it does and
than comes back have it analyzed for exhaust/CO in the coolant.
Larry

 

Today I had the cooling system flushed out and the thermostat
replaced. The heater was blasting out hot air for the duration of the
drive home. Got back in the van a few hours later and only cold air
was blowing even after the engine was completely warmed up.
How does one check for exhaust/CO in the coolant? Is there a device I
can buy or do I need to take it back to the shop?

 

There is a device that goes into the radiator neck. It uses a chemical that
changes color in the prescence of CO. judging from your symptoms though and
the fact it's a mitsushitti motor I'd put my money on a bad head or head
gasket(s). Top end engine problems are quite endemic to that engine.
Larry

 

Thanks Larry. I'll check it out. It wouldn't surprise me if it is the
head gasket. The engine is leaking oil ( had the valve cover tightened
up but I think it's still coming out). Also this engine may have
overheated at one time because I noticed a discoloration (gold brown)
high up on the dip stick. Didn't think much of it at the time. Over
heating may have caused the head to warp maybe? Back to the shop

 

The mechanics at the shop told me I'd have to replace the head gasket
and have the heads planed in order to get heat back. They checked the
CO in the coolant and said there was exhaust seeping into the coolant
from the faulty gasket. The estimate was $1350.00 cdn.

I brought it to someone else and it turns out it was just a mechanical
problem in the climate control dial. The switch was malfunctioning.
Took it apart and found that a small ball bearing was out of place.
Put the bearing back in place and we got heat right away. The dial is
working like it should now in that it clicks in place at every setting
instead of turning smoothly around with no click at each setting.

 

Before you spend your hard earned money, check a few things first:

1) With the car warmed up (15 minutes of city driving), check the heater hoses
at the firewall. See if both or one of the hoses is warm. If only one is awarm
and the other cold, you have a blocked heater core. You can try to fix it by
power backflushing. I had a saimilar problem on a Dodge and 5 minutes of power
flushing after pouring some household bathroom lime and rust cleaner for few
hours, solved the problem.

2) If both the hoses are cold, coolant is not being pumped to the upper area of
the head. You will need to purge the cooling system of all air. One quick way
to do it is to open the radiator cap, place the car with the front end higher
than the rear (like a ramp etc.) start and warm up, until upper radiator hose
becomes warm. It should purge most of the air. Then fill to capacity and leave
the cap off for 10 minutes to let more air bubbles out.