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3.0 93 Ply Voy. No Heat

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11 replies to this topic

#1 David Nuechterlein (converted)

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Posted November 9, 2004 at 12:42 pm

93 3.0 198kmiles 3 speed auto,ply. voy. ac . Heads replaced head gasgets replaced at 186 k miles .Problem: Temp guage varies from mid point and lower . Loss of heat at stop lights if I rev moter a bit heat returns , I have tried three differant thermastats some work better then others but heat is not as good as it use to be . Checked vac Valve even locked it open . Reversed flow in core . Core hoses hot on one side cooler on otherside . At freeway speed temp guage holds at mid point and heat is ok but not roasting like it should . Water pump has been replaced twice . I even checked for traped air .... I will check again ..took hose off of core and let flow in bucket looked ok I think ... what is ok I guess ...
I am about to flush heater core only with vinagar or Miratic acid .
Please note this has been a problem since 150 k miles and it seams to have gotten worse .
I am stumped any ideas .
Any improvements for the not so stellar head lites on these things ?
David Nuechterlein djnuecht[at]delta.edu

#2 bhp02

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Posted November 9, 2004 at 06:52 pm

if temp of engine is low, then it is not your heater, core,
your engine is not operating at normal temp.
Check your thermostat again, I would use the mopar one
with the autmatic bleeder for trapped air... atleast that is
what I think I had, also you may just have air trapped in it.

#3 johnnj

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Posted November 9, 2004 at 06:55 pm

Sounds like you covered most of the bases here...but make sure you are getting a strong flow to the heater control valve and it is fully opening. The hose should be hot as heck. If it is, I'd say either the heater control valve is stuck and /or the heater core is plugged. Is your radiator cap good(16 lbs) so the radiator can build up to the right lb. pressure?

#4 David Nuechterlein (converted)

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Posted November 9, 2004 at 08:13 pm

Tomorrow I am going to the Mopar dealer and getting there version of a T stat ....I have done this before with mixed results but I will try again .
I had a Mechanic tell me that there was a chance the pump could have a impellor that is backwards ......he states he has seen this but is not sure on my model of engine . He also stated that it will pump water but at a reduced rate ......... any merit to this Idea . I hate to pull all the power drive area just to check this pump . Not a easy guy to get to buy no means . What bothers me is I had a faulty pump when I put the new heads on . it started binding two hundred miles after I put it all together ......so I put another one in . I love the van it is very good shape and I just replace the original fuel pump at 197kmiles ( major grove's in the rotor and was down 8 psi from spec) and a Map sensor . The motor is strong . Just this heater thing is doging me .
It takes a long time to warm up at idle in the morning after 15 min it barly moves the guage .......I know T-stat ...... I hope it clears it up but I am pessimistic that it will after three t-stats in 30 k miles .
Still open for Ideas .
Dave N

#5 johnnj

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Posted November 10, 2004 at 06:23 pm

Something is wrong for sure and it sounds like one of those "stupid" kind of things. Are you sure the radiator cap is good...16 lb cap being used? Is the tstat installed properly with the copper spring part inside the head? If you empty some radiator coolant, maybe 1/2 of it, observe the flow by looking in the radiator, it should be going through the fins and try to observe when racing the engine...it should be strong. If not maybe that reversed impeller on the water pump? Your radiator can be in bad shape...are you sure the radiator isn't clogged as well?

I have a 91 3.3 and the temp goes to the 1/2 mark in a very short drive or about only 5 minutes. It stays at the 1/2 mark thereafter. Your 15 minute warmup is way too long.

Edited by johnnj, November 10, 2004 at 06:26 pm.

#6 geeaea

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Posted November 10, 2004 at 09:36 pm

I'm with bhp02

Your temp is going low on the gauge. t-stat. Don't assume that you can't get a defective one or two. The loss of the little heat you have at stop lights is the flow rate not the temp. You're just cooling off the warm water even more with a low flow rate.

Either MOPAR or NAPA.

#7 David Nuechterlein (converted)

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Posted November 11, 2004 at 10:17 am

Picked up a Genuine Mitsubishi T-stat from the local mopar dealer . Ouch the Mitsubishi feeling ......25 bucks for a T-stat . this thing sure is built better then the car quest one I bought . I hope to put it in this Sat . I will let ya all know the results . I am going to drive the van up on ramps again and "burp" it agan just to make sure there is no air .
Dave N

#8 David Nuechterlein (converted)

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Posted November 18, 2004 at 05:10 pm

Ok A update. Installed the Genuine Mitsubishi T-stat. This solved the temp guage fluxuation . And made a bit of a differance in heat .The auto parts store stat was cheaper built and stamp 88 C where the Mitsu. Stat was a lot heaveir and substantialy better built . The Mitsu. Stat was marked 90 C. But the heater is still not up to snuff when it gets below 25 degrees . I wil flush the heater core next with a chemical flush a pump and a 5 gallon pail .
David Nuechterlein.
More updates to come .

#9 John Wood

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Posted November 18, 2004 at 06:10 pm

I think a chemical cleaning of the heater core will help, but be careful what chemicals you use. You mentioned Muratic acid in an earlier post. This is just a reduced concentration of Hydrochloric acid and will eat through the pipes quickly.

My method is to go out and buy extra heater hose and attach a 16 inch or so length to each pipe and turn them up. On one side, I put on a funnel and add concentrated cooling system flush. I continue to add a slightly diluted mixture until the fluid begins to bubble out the other hose. It takes a bit for the air to burp out. I let that mixture sit for 20 to 30 minutes (using a bungy cord to hold the hoses up) and then flush it out thoroughly with a garden hose. This might need to be done twice, going in the other direction.

Note: I have never ruined a heater core doing this, but can't be responsible if yours eats through (I don't think it will).

Another thing; I replaced some of the long heater hoses on my old van just because they were old and I thought it would be wise to prevent a potential burst hose. I saved the old hoses and about a month later I was cleaning the garage and tossed these on the floor. Much to my surprise there was a lot of dry scale that fell out. As I banged these hoses around, large amounts of scale began falling out. The point is, old hoses do get a build-up in them and the passageways clog, just like plaque in an artery. Old hoses should be replaced, even if they look good.

I think your water pump is fine. If it was bad or turning the wrong direction, your engine would overheat; not the opposite. You are making progress. Good luck and keep us posted.

#10 David Nuechterlein (converted)

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Posted November 19, 2004 at 10:54 am

Installed new hoses last year ( 186,000 miles ?) when I replaced the heads
As for the chemical flush that is what I had planned to do . I will use the approved rad flush stuff with the method you listed above . No need to do the rest of the engine it was very clean when I pulled the heads . 1 thing I did forget to mention . Back around 150 ooo miles a local mechanic put rad seal (the ground up silver powder stuff) in to system . He was trying to elimnate the mysterious antifreeze disaperance . Had I known about the notoriuos head gasket problems that the 3.0's had I would have never let him do it .
As the heater was already not as good as it should have been then. I do not think this is the problem BUT i am sure the sealer could have added to it . Lets hope there is some build up in there and the rad seal stuck to it , and it all washes out . If not that core is a monster to get out ......... (I) will be come one with your dash for sure !!!!!!
why do they do that ?
Dave Nuechterlein

#11 John Wood

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Posted November 19, 2004 at 02:49 pm

I noticed that on my 96 GV, they redesigned the system to where you can get the heater core out without removing the entire dash. With the airbags and all under there, I guess ir was just becoming too major a job.

#12 Dave H

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Posted November 24, 2004 at 02:28 pm


I HAD this exact same problem from the day I drove it off the lot....brand new.
The FRONT heater was wimpy at best but the REAR heater would roast me outta there. Living in Southern California though did not make this a big deal so I just got on with my life.
Jump ahead 15 years and 203K miles later....by this time the front was blowing cold and the rear was still roasting but I am retired now so I got busy and looked into this......
Both hoses on the front core are hot.....so what the heck??
Just to jump to the chase.....there is a vacuum operated diverter valve in line with both front and rear cores.....this valve has a small hole in the vacuum operated flapper and reduces flow to the cores when the heater is off.
The vacuum motor operated ok as seen by the movement of external rod on the diverter BUT......in messing around with it I fortunately broke the plastic outlet going to the rear core so I replaced it with a new one for $25 and VOILA.....roasting heat from both front and rear.
The only thing I can think of is that the internal flapper was loose on the shaft and was not opening to allow unrestricted flow even though the vacuum motor was moving.
After I removed the old diverter, I could look straight through it so it was not plugged up.
Hopefully, this will be your problem too.




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