Engine/Transmission (1994 - 1998) poll on 12 valves with poor heat

[TBurow]

i am trying to form a poll to determine which 12 valve owners have poor heat. all 3 i have or had have poor heat. 1 96, 1 95, and 1 89. all automatics. i am wondering if the manual trans equipped vehicles have better heat due to not having the trans cooler to split the coolant flow that would go to the heater core. if the manual trans trucks have good heat i may try to reroute the coolant to go through the heater core and then to the trans cooler in a loop increasing the volume of coolant through the core. instead of half to each.



just a thought. if it works it will be great for alot of us.

 

[Skydiver]

Got great heat, just takes 6 miles to start feeling it.

 

[Missouri Mule]

Same here good heat takes about 5 miles for engine to warm up but I get some heat before that.

 

[KOG]

Diesels don't waste as much fuel as heat at part load. And you've got 1200lbs of engine to warm up too. Unless you moving fairly fast or with a load you're just not going to get a lot of heat. Used to have that problem with /6 cars too. You can block the radiator and improve the situation as long as you remember to take the curtain off of it before overheating.

 

[Hammer]

Mines a 5 spd and I have never had any heat issues at all.



Well I guess I can not say that actually as I did actually once around 100k. It was when the gentleman who was servicing my truck fixed a antifreeze leak at the thermostat housing and got all the needed parts from NAPA instead of Cummins. The NAPA thermostat was a POS and the truck never made any heat at all. I tore it apart and installed the updated thermostat from Cummins and its been fine for the last 120k... ..... Andy

 

[SRath]

My 5-speed puts out great heat. You have to condition yourself to ignore the endless cycling of the temp gauge in the winter, though.

As an aid to warmer engine temps in winter, I use a piece of thin, tough plastic slipsheet used instead of palletizing on some goods. I cut a small flap, about 5 inches square, in the middle and leave a few inches sticking above the radiator which just folds over when the hood shuts. The extra foldover makes it easy to remove. When it gets subzero, like now, I close the flap and reinsert it between my intercooler and radiator. As the temps soar to the balmier teens and twenties, I open the flap. It is weatherproof, ultra light, rolls up compactly for storage and has lasted for a decade. The price is right, too, since I'm a truck driver and simply fished it out of a dock dumpster. I keep an extra full sheet (rolled up) in my truck for use as an emergency creeper. Very handy trash!

 

[JLEONARD]

My ex, the 91 5 spd, had awsum heat. Yes it would take 4 or 5 miles to fully open the T stat, but the heat would literally drive me out of the cab even on a sub zero day.

I drove the truck empty most of the time

 

[CCiatteo]

I have great heat also. I plug in at night to aid in start up, but don't think that has a huge effect on the heat output. It still takes about 5-7 minutes before the heat comes on. Once its pumping though I don't even need to use the fan, I just use the flap doors to direct where to let it radiate from.

I do notice that plugging in at night helps the hydraulics of the clutch and the power steering seems to not moan and groan as much, kinda wierd?

Chris

 

[WDixon27]

the heat in my 96 sucked BAD up till i replaced the cummins branded thermostat i installed right after i got my truck 4 years ago, i got a MR gasket brand 180* unit for a big block mopar, it dropped right in and works like a champ, it runs cooler in the summer and now that its cold i am starting to feel heat in 2 miles with no radiator air blockage, before with a air blocker id not get decent heat till i was almost at work after a 16 mile interstate run, i installed the MR gasket unit this spring and wondered how it would handle heat and its great

 

[fest3er]

At 15F, I can get good heat within a mile if I pre-work the engine: while sitting in the driveway, put it in gear, stand on the brake, and rev it up to 10# of boost and hold it there until the EGT reaches 800F (2-4 minutes). I've also been known to set a throttle stick to move the pedal about 1/8", set the parking brake and come out in 10 minutes to a toasty warm truck. Some day I'll separate the parking pawl operation from the shift lever so I can keep the pawl engaged with the trans in gear. (Either that or install a 'trans brake'. )

If you aren't towing or hauling hard, you can cover the entire radiator when it's below 0F with no worries, and cover half from 0-40F. Merely check your engine temp gauge now and again to be sure, though.

Manual trans owners are left to using an exhaust brake to pre-work the engine; they seem to work well enough.

Finally, if you can beg, borrow or steal a fiber scope, check the leading (air) side of your heater core. After 13 years, it might just be plugged up, providing insufficient air flow for good heat transfer. Soon's it warms up, I've got to take my dash apart and replace both the heater core and the evap. After seeing what the evap in the house looked like after 20 years, I wouldn't be surprised to see the truck's heat exchangers nearly plugged solid.

 

[Ol'TrailDog]

I've had three 12Vs and other than it takes a while longer than other vehicles the heat is fine. I do put a plastic sheet in front of the radiator during the winter, and usually figure out it is time to remove it in the spring when I start wondering why the truck is over heating



I've never bothered to use the exhaust brake to quicken the warm up period. I figure being cold for a couple minutes more helps make me just one tough hombre.

 

[TBartlett1]

Bought my first CTD in 1990 and it had good heat.

1 1990 W250 5 spd good heat.

2 1990 W250 auto good heat.

3 1992 auto good heat.

4 1999 auto good heat.

And my most recent a 1990 W350 auto good heat.



The Cummins needs to be worked or a good drive of 5 to 10 miles to completely warm up. My drive to work ranged from 24 to 62 miles.

I blocked up to 50% of the radiator (weather dependent) if used only to commute, no towing. This reduces hot/cold temperature swings on the temp gauge.

If you block the radiator block the drivers side to help keep the injection pump warm.

I found my automatics warmed up slower than the manuals but heat output was actually better once everything engine & transmission was warm.

Flushing & cleaning the cooling system may help and you may even want to back flush the heater core.

If the cooling system is not maintained rust particles may be generated and cause the thermostat to stick open, a new thermostat will stick also. I know it happened to me.

A very, very though flush with a cleaner and the addition of a coolant filter was needed to resolve my problem.

The first Gens had a service bulletin that addressed erratic temperature fluctuations.

The new Mopar thermostat came with a template to use as a guide to remove metal from the head casting that interfered with the free action of the thermostat.

In general all my CTD's have had good to excellent heat.



Currently I have 3 CTD's.

Truck #1 completely stripped due to body rot & sent to scrape yard and over to China to make cheap brake rotors.

Truck #2 cracked a head and now has the engine & transmission from #1

Truck #3 sold

Truck #4 a 1999 twin turbo p-pumped 24v is waiting for some love.

Truck #5 recently bought in California and will be my summer ride.

I love my 1st Gens.



Tim

 

[TBurow]

i have a new heater core, good thermostat (temp stays at 190), keep it plugged in and dont get good heat for 10-15 miles. it just seems like there is not enough heat coming out. its about 80 degrees coming out of the vents after 10 mins. even with blocking most of the radiator the heat still sucks. i dont think the blend door is broken i can hear it open and close.

 

[fest3er]

i have a new heater core, good thermostat (temp stays at 190), keep it plugged in and dont get good heat for 10-15 miles. it just seems like there is not enough heat coming out. its about 80 degrees coming out of the vents after 10 mins. even with blocking most of the radiator the heat still sucks. i dont think the blend door is broken i can hear it open and close.

Hmmm. Engine is at temp. Radiator is blocked. Tepid air comes out. This doesn't right at all. Even at -20F, I'd get decent heat with the radiator blocked.



Pondering out loud:

• Did you install new heater hoses as well? Were the head/block heater ports were open or clogged?
  
• Is there an air pocket in the heater core? (If the heater core has a gazinta and a gazoutta, might you have swapped the connections?)
  
• Are you sure the t-stat is good? (Years back, mine was bad: the gauge rarely budged much, but the internal temp would read 230F+; the t-stat was bad. )
  
• Are you sure the blend door is functioning properly?
  
• Does heating change much if you open the recirc door (switch to Max)? It should heat much quicker in recirc, but would also fog the windows.
  
• Is the fan blowing well?
  
• Is the radiator full?
  
• Is the overflow bottle filled to the right level?
  

 

[KYOUNG]

My 94 5 speed always warmed up quickly, would blow warm air idling in about 5 minutes, my 1990 5 speed would warmup fast with the idle locked up higher, But my 1998 Automatic takes forever to warmup. If you are going to drive it you might as well just get in and go because it wont warmup idling. It will blow warm air out of heater if it ever warms up... been through 4 thermostats in the last year replaced waterpump hoses and radiator, blocked the radiator with a large piece of plywood, been tempted to take the fan off and try that!!

 

[LHastings]

My 98 has been cold since the it came out of the factory. I just replaced the thermostat with a new one from cummins and now it run even colder. The heat gauges needle just runs in the normal range. With the temperature here running down in the single digits and warming up to the 30's. My heat coming out of the vents is in the low 90's. I removed the ac clutch fuse so I can run the recirc. air, it help I can now get low 100's out the vents. Cummins could not tell me what the stat was rated at. I'm going to buy a 190 third party vendor and see if that helps. If that don't help I'll block the radiator.

 

[bmoeller]

Have had good heat in the '97 (auto) with a 180* Cummins stat. The '99 makes good heat as long as you are driving and making some power. Let off to come down an off ramp, the air coming from the vents cools of VERY quickly.

Cardboard zip tied to the back side of the grille.

 

[SRath]

Just my theory and opinion, but I do not like blocking the intercooler; it defeats the purpose. I like to slip plastic behind it to block the radiator only.

 

[TBurow]

fluid is full, have plenty of heat in the engine, replaced the heater core a year ago, hoses on right, hotter on recirc, just not right. i will check the volume of coolant through the hoses. blend door works it gets really cold if i switch it to cold and i looked at it when i did the core and it was in 1 piece.

 

[bmoeller]

Just my theory and opinion, but I do not like blocking the intercooler; it defeats the purpose. I like to slip plastic behind it to block the radiator only.

The CAC gets plenty of air with the cardboard attached to the grille. In these temps in the winter, the gap between the grille and CAC provides plenty of cold air. Plus, I don't block off 100% of it anyhow. No change in EGTs on or off the truck going down the road.



If you stuck the cardboard between the condenser/trans cooler and CAC, then I'd see there being a problem.