Heat/Overheat Problem

[jasontiff]

So, I've had a problem with the car ever since I got it 2 years ago, but have only noticed it recently. This is the breakdown:

A.) My heater doesn't work. Up until last fall, I never had a top, so I could never tell if the heat was on or not; I just assumed it was. In the summer when I wanted to bring engine temps down I'd run it, and of course it'd blow hot on a 100˚ day but that's only because of ambient temperatures. In the winter I could never feel it anyway, but once I got the top I noticed it blew cold air. The only heat in the cabin comes from the motor, sidesills and transmission seeping in.

B.) I've always had overheating problems, even on cooler days. The early Gen. Is have a yellow area right before the red (probably the 230˚ mark or so) and my car will run right at that, or even right up to the red. I rode in Ryan's car for the first time last week, and even with 90% humidity, it being 80˚ outside and him romping on it, it never even got to 190˚. Our setups are essentially the same, except his car is a year newer and he has the lower thermostat (I swapped mine back out for stock when we did heads/cam).

C.) When we were refilling the cooling system after the heads/cam, we filled from the heater hose. At one point the coolant essentially stopped flowing for a minute or two, then suddenly let go. I hooked up a garden hose to one heater hose and a drain hose to the other and flushed it (albeit with low pressure), but nothing significant came out and I still have the problem.

D.) When we did the heads/cam, the engine temp sensor was relocated to the other side of the block (after the coolant has passed the first side) so the temp gauge shows about 10˚ warmer than it normally would anyway.

E.) The radiator and fan are stock, but the radiator was rotted and recored while it was out. The shop said it was 60% blocked, so radiator flow isn't the problem.

This leads me to believe that there is a blockage in the heater core somewhere, preventing my car from running as cool as it should. How hard is it to get to the heater core and/or replace/clean it? If it sounds like it could be something else, let me know. Thanks!

 

[dave6666]

How much beer we talking here for the heater core crew?

Yeah, if a garden hose (30 - 40 psi) won't put water through the core, then ya got a problem with da core.

I think you have to yank the AC to get at it.

 

[jdeft1]

Water pump impeller damaged??

If the heater core flows with a garden hose... it may be time to check the pump. What was the radiator blocked with??? Maybe the seame junk ruined the water pump???

my .02

 

[jasontiff]

Dave, I'll gladly inebriate a small army to get this thing running cooler. Now that it's heating up down here running the heat isn't as cute as it was. You coming to the drive Saturday?

I replaced the water pump when we did the heads/cam, so that shouldn't be the issue. It's only a few months old.

 

[dave6666]

What did the passages inside the block look like when you had the heads and water pump off, from what you could see?

Do you have the upgraded fan?

 

[jdeft1]

Did someone put stop-leak in it???!! What clogged the radiator? Same thing that's clogging the heater core I'd bet! I probably don't need to ask if you're sure the heater valve is working...
- J

 

[jasontiff]

I've got the stock fan, with it's obnoxiously funky early 1993 shroud. I've been meaning to wire in a manual fan switch but haven't yet.

In all honesty, I was more or less a set of hands and a laborer when it came to the swap. My friend was the brains behind the operation, so hopefully he looked at the passages because I didn't know to.

 

[Sweet Ride]

Tempe Sensor or Gauge could be bad.

As far I as can tell, the temperature switch on the dash is connected to a water valve via a cable. If that water valve was jammed or the cable was stretched, that could cause a no heat issue. That could also be the "blockage" in the heater core.

When they rebuild radiators, they ROD them out not ROT them out. If it was rotted out it would give you a whole mess of other problems.

 

[jasontiff]

Did someone put stop-leak in it???!! What clogged the radiator? Same thing that's clogging the heater core I'd bet! I probably don't need to ask if you're sure the heater valve is working...
- J

The shop didn't say what clogged the radiator; just stated that it was 60% blocked. The heater valve is working.

It's the weirdest thing. I hadn't thought of the passages in the block, but other than that and the heater core, essentially everything has been rebuilt or is brand new.

 

[jasontiff]

Tempe Sensor or Gauge could be bad.

As far I as can tell, the temperature switch on the dash is connected to a water valve via a cable. If that water valve was jammed or the cable was stretched, that could cause a no heat issue. That could also be the "blockage" in the heater core.

I'm guessing testing the sensor and gauge requires some fancy multimeter work? I'm trying to remember if we reused my working sensor from before or picked up one that was laying around.

I believe we checked the cable to the valve before and took the hoses off to make sure we saw daylight when it was open, but I'll look again.

I just figured since I had both a heater and overheating problem, the core could be causing both. Hopefully it's not a separate problem for each (in which case I'll just buy a GTS)

 

[Sweet Ride]

The issue with the heater not working could be a vacuum problem or blower box door issue as well. I know that doesn't help with the overheating but it could solve one problem.

Owning different models, I can't say exactly what your temp sensor would ohm out at. According to the GEN II book, it should read between 7000-13000 ohms at 70*F.

I say get the GTS and keep the RT/10

 

[Dan Cragin]

Give me a call, there are many variables on the gen 1-2 cooling system that could be the problem.

 

[TexasPettey]

If you run at 70MPH in 6th gear, does the car get down to the 190deg range? If so, drop down to 20MPH in 2nd gear. If it gets hot, I'd suggest that you don't have a water flow problem. You probably have an airflow problem. At 70PMH in 6th you're only around 1500RPM, and the water pump isn't cranking too fast. If the car runs at normal temp, it's probably because the radiator is finally getting enough airflow.

Check the radiator, A/C, and oil cooler for visible air obstructions (bugs, rocks, etc.). That will hinder the airflow.

Turn on the A/C while the car is idling in the garage. Does the fan kick on and drop the temperature down? If not, you may want to consider swapping out your fan assembly for the Gen2.

If you run at speed with low RPM, and the temp is still high, there's probably an obstruction somewhere.

If you don't think the heater core is functioning, check the lever arm to it and make sure it is moving. There is also the possibility of a vacuume leak in your vent baffles.

Also, now that you have more HP, you're going to generate more heat.

 

[dave6666]

A few more comments...

-> I've driven 2 nearly identical GTS's (mine with Roe duct, the other without) and my car runs 5 - 10 degrees hotter by the gauge. What do I credit that to? Gauge inconsistency, not the coolant temp. Or maybe the sending units too, as the 5 - 10 degree difference I'm talking about is where the fan kicks on too.

-> The temp in my car goes up with the AC on (in traffic), contrary to the belief that with the fan forced on your coolant temp will go down. I attribute this to the temperature of the coils in front of the radiator preheating the air. Yup, even when it's 110 outside, a 170 degree condenser is preheating the air to the radiator. I did verify this with my IR.

-> Speaking of an IR thermometer, if you have one shoot the water neck coming out of the block. That should be your engine coolant temp. Or the metal hose ****** at the top of the radiator where the upper hose is if you can't access the water neck.

-> It was mentioned the HVAC duct work may not be functioning properly. But it does blow right? Just not hot air?

-> The coolant temp in my car will start to rise as my speeds decrease to 50 mph or so. I have to be doing 70 to hit the lower operating temp.

 

[97GTS]

Another thing to think of: Is the cooling system proberly "burped" ie no air in the system. I'm sure you have thought of that but just in case.


Ron

 

[jasontiff]

A "good" temp for me is about 220˚-230˚; that's about as low as it goes, even on a 50˚ night cruising at 70 in 6th...if I'm lucky.

The system has been burped a number of times after I decided hose clamps were overrated and shot coolant all over my VEC...but it earned me a ride in Dave's car to the liquor store, so it was worth it!

The system blows air, but it's just not hot. The AC works flawlessly, and the heater "works" when the ambient temps outside are hot, but in the winter it's cold.

 

[dave6666]

Do the hoses to the heater core feel hot? Therefore indicating flow?

If your heater hoses are indeed hot then it doesn't appear you have a flow problem there. Maybe a cat stuck in your duct work?

Anyway, assuming the heater not working is a duct problem, that should not be the cure for what you say is a hot condition. Using the heater for additional cooling should be for emergencies, not daily operation. You might want to consider these to be separate issues, depending on whether you have flow to the heater core.

 

[jasontiff]

I've been emailing David Weaver at A.R.T. and he said that it's been a while since he's worked on an EARLY Viper, but he remembers 2 specific cases where the cars were bought back by the dealership because of overheating. I guess they're notorious for that. Rear antennae = hot car

In his experience with the 1992-1993 cars he said an upgraded fan and radiator usually fixes the problem, along with relocating the coolant bottle to the fender (my overflow tank is in the fascia and the radiator cap is on the radiator).

I'll run the car today and see if running the AC brings down the temp and I'll see how warm the heater hoses are too. I may "rent" an IR thermometer from Autozone too.

 

[Tom F&L GoR]

I have a '94 but can affirm that the Gen 2 radiator fan will significantly reduce temperature excursions. By more than expected. The old radiator and new fan shroud have a different stud pattern, so you have to play with how to attach the fan and modify the electrical plug for the fan to wiring harness.

When is the last time you changed the radiator cap? If it is not sealing and creating pressure, you will get localized boiling and poor cooling, bubbles forming, etc, etc. Get a cap with a spring-loaded center like on newer Gen 2 (ha, a "newer Gen 2"?!) and not a dangling drop center cap as was OEM. If the overflow tank is out of sight, you might be missing some visual clues.

I also see the overheating problem separate from the heater core. The heater core shouldn't be the determining factor as to whether the engine stays cool enough. Prove this by bypassing the heater core altogether and drive around to see what happens temperature-wise.

 

[bluesrt]

if the radiater was plugged that bad-60%- is bad,then the heater core is more than likely *****- can you find the heater hoses going to the core,get it hot at idle,see if the hoses going to the core at the firewall are a differant temp,if they are,thats the next obvious step to go to next.

 

[jasontiff]

I have a '94 but can affirm that the Gen 2 radiator fan will significantly reduce temperature excursions. By more than expected. The old radiator and new fan shroud have a different stud pattern, so you have to play with how to attach the fan and modify the electrical plug for the fan to wiring harness.

When is the last time you changed the radiator cap? If it is not sealing and creating pressure, you will get localized boiling and poor cooling, bubbles forming, etc, etc. Get a cap with a spring-loaded center like on newer Gen 2 (ha, a "newer Gen 2"?!) and not a dangling drop center cap as was OEM. If the overflow tank is out of sight, you might be missing some visual clues.

I also see the overheating problem separate from the heater core. The heater core shouldn't be the determining factor as to whether the engine stays cool enough. Prove this by bypassing the heater core altogether and drive around to see what happens temperature-wise.

I'll start looking around for a Gen. II fan. I looked into it last year, and in the 6 weeks that passed between the time I inquired and the time I was ready, Dodge doubled the price. Jon B or Chuck actually posted a thread about it when we discovered that.

My radiator cap is an anodized one I got 2 years ago (maybe Roe?). My overflow tank is visible through a cutout in the wheel well, but since it's plastic and because of it's location it's hard to see much more than the level of the coolant.

I'll try and bypass the heater core and see what happens. Does anyone know what size the heater hoses are off the top of their head? I can go home and check first but it'd be easier to just swing by Autozone on the way home. I want to say 1 5/8" or so. Like I said, I hope that the heater and overheating problem are one in the same, and I can knock this out in one fell swoop, but if it isn't I guess I'll get it figured out.

Thanks again to all for the input!

 

[dave6666]

I want to say 1 5/8" or so.

Heater hoses might be 5/8, but not 1 5/8.

 

[-FROG-]

Can you bypass the heater all together? Route a hose to bypass the heater core if you can. That's what we used to do on our 5.0 Mustangs all the time.

 

[Tom F&L GoR]

I'll start looking around for a Gen. II fan. I looked into it last year, and in the 6 weeks that passed between the time I inquired and the time I was ready, Dodge doubled the price. Jon B or Chuck actually posted a thread about it when we discovered that.

My radiator cap is an anodized one I got 2 years ago (maybe Roe?). My overflow tank is visible through a cutout in the wheel well, but since it's plastic and because of it's location it's hard to see much more than the level of the coolant.

I'll try and bypass the heater core and see what happens. Does anyone know what size the heater hoses are off the top of their head? I can go home and check first but it'd be easier to just swing by Autozone on the way home. I want to say 1 5/8" or so. Like I said, I hope that the heater and overheating problem are one in the same, and I can knock this out in one fell swoop, but if it isn't I guess I'll get it figured out.

Thanks again to all for the input!

If you mean the anodized cap is a sacrificial anode cap, I suggest getting a normal cap. There are other explanations, but my view is that they were used in marine applications where antifreeze (and anti-corrosion additives) was not an option. So the corrosion of the engine was managed by offering an easy corrosion target, easier than the block or heads. Putting these caps in automotive use: the anode will still "try" to corrode, but the additives in the antifreeze will try to prevent this. You use up the corrosion protection in the battle between the cap that wants to corrode and the coolant that doesn't want to let it. It leaves less, little, or no corrosion protection for the engine.

 

[jasontiff]

If you mean the anodized cap is a sacrificial anode cap, I suggest getting a normal cap. There are other explanations, but my view is that they were used in marine applications where antifreeze (and anti-corrosion additives) was not an option. So the corrosion of the engine was managed by offering an easy corrosion target, easier than the block or heads. Putting these caps in automotive use: the anode will still "try" to corrode, but the additives in the antifreeze will try to prevent this. You use up the corrosion protection in the battle between the cap that wants to corrode and the coolant that doesn't want to let it. It leaves less, little, or no corrosion protection for the engine.

I hadn't heard that theory before, but it makes sense to me. I still have the stocker, so I may swap that while I'm in there screwing with everything tonight. Thanks!

 

[jdeft1]

All good suggestions IMO. The heater core and overheating problems are probably seperate issues (unless the whole engine is clogged with junk).

Your fan *****. I really like the Alan's Performance radiator in my '94. Buy it along with a gen 2 fan! (bolts right up, just have to cut and solder three wires). It made a big difference for me...pricy, though, for the pair. My gage climbs to approx. 225deg. the fan comes on and cycles off at around 180 like clockwork.

Tom's right...a bad cap will cause it to overheat.

Good luck.

 

[got one]

A couple of quick points for reference:
1. Jason's radiator and fan setup in the 93...COMPLETELY different than a 94 and 95 (he can explain why) so some of our Gen 1 solutions won't work very well with him...replaing the fan shroud and such on his car is a pretty big deal...not like the later Gen 1's...Jason, maybe time to tackle that project and put a later model cooling setup in there?

2. Gen 1's can cool just fine with the Stock radiator and Stock fan...mine is living proof. I stay cool (average 190 but never get above 220 even with traffic) on 110 degree days on spirited drives air conditioned drives through the Texas heat with the following setup:
a. Stock Radiator
b. Stock Fan
c. Roe fan kit
d. Roe silicon hoses
e. 172 thermostat
f. waterwetter
g. hi-flow cats
h. 50/50 mix water coolant
i. OEM radiator cap (recently bought)
j. burped system


And yes, during cold (40-60) weather my average is around 180 and it runs fine

Hope this helps.

 

[vip06]

I'll start looking around for a Gen. II fan. I looked into it last year, and in the 6 weeks that passed between the time I inquired and the time I was ready, Dodge doubled the price. Jon B or Chuck actually posted a thread about it when we discovered that.

My radiator cap is an anodized one I got 2 years ago (maybe Roe?). My overflow tank is visible through a cutout in the wheel well, but since it's plastic and because of it's location it's hard to see much more than the level of the coolant.

I'll try and bypass the heater core and see what happens. Does anyone know what size the heater hoses are off the top of their head? I can go home and check first but it'd be easier to just swing by Autozone on the way home. I want to say 1 5/8" or so. Like I said, I hope that the heater and overheating problem are one in the same, and I can knock this out in one fell swoop, but if it isn't I guess I'll get it figured out.

Thanks again to all for the input!

The radiator cap from roe may be one of the problems from overheating! I had one on my gen 2 that would not hold back pressure. My car would get hot, so I put my factory cap back on and no more problems.

 

[Tom F&L GoR]

A couple of quick points for reference:
2. Gen 1's can cool just fine with the Stock radiator and Stock fan...mine is living proof. I stay cool (average 190 but never get above 220 even with traffic) on 110 degree days on spirited drives air conditioned drives through the Texas heat with the following setup:
a. Stock Radiator
b. Stock Fan
c. Roe fan kit
d. Roe silicon hoses
e. 172 thermostat
f. waterwetter
g. hi-flow cats
h. 50/50 mix water coolant
i. OEM radiator cap (recently bought)
j. burped system


And yes, during cold (40-60) weather my average is around 180 and it runs fine

Hope this helps.

Putting the fan in a '94 wasn't that easy - I was lucky in that the fan was a part of a warranty claim so I actually got a new fan and radiator at the same time.

Your list - the cooling system has to keep the temperature above a minimum as well as prevent excursions above a maximum. The 172 thermostat must be open all the time if you average 190 and run up to 220?!

In warm weather areas you could use 100% water and a corrosion package like the Zerex Racing Super Coolant (NOT water-wetter!) The Zerex bottle is about a quart and contains the additives that you get in the ethylene glycol gallon when you buy "anti-freeze." Your corrosion protection would be there, but the water provides much better heat transfer. Glycol has only half the heat transfer capacity; a 50-50 mix has 75% of the heat transfer of water.

I'd lilke to see the effect of just the rad cap change before you spend money.

 

[got one]

Your list - the cooling system has to keep the temperature above a minimum as well as prevent excursions above a maximum. The 172 thermostat must be open all the time if you average 190 and run up to 220?!

So far so good ...I have been running that way for at least 3 years now and hot or cold weather it acts and performs fine...granted during a really cold day with winds, it might take 5-10 minutes to warm up, but given here in Central Texas the weather is above 60 (for my driving) 90% of the time.