Dodge truck overheating help

[rtimgray]

I've got a 1997 Dodge 1500 truck with the 5.9l v-8. I bought it about a year ago. Shortly after I bought it, I noticed that it seemed to be running hot. Correct temperature is 190 degrees. The gauge shows 200 degrees to be normal, with 250-260 overheating (well, that's as far as the gauge goes. I assume anything over 200 is overheating). Anyway, I changed the thermostat, did a flush and fill for the radiator, all that kind of stuff - nothing different. The gauge indicated hot (anywhere between 220 and 250 after I drove it a while), but it wouldn't actually boil over (do new vehicle's boil over anymore?).

I had it checked at a Dodge dealership, and they said they couldn't find anything wrong. They said even when the gauge was reading 220 to 250, the temperature on the manifold at the thermostat and on the thermostat outlet hose was 190 degrees (they measured with a laser gun). They said it was either a bad sending unit or bad gauge cluster - either way, nothing was actually wrong with the cooling system.

So I drove it all winter and now back to this summer (I didn't drive it alot last summer because I mostly drove my Samurai. However, my Samurai transfer case went out last fall and I have been trying to find a cheap one locally - no luck. I have finally ordered one online that should be here next week). Anyway, no problems all winter. Now this spring, there have been a couple of days when I get home from my commute of 11 miles from work, and the gauge is pegged and after the truck is shut off, in just a minute the coolant starts pouring out of the overflow tank. I thought this just might be because I had put too much coolant in it (more than halfway up the overflow tank). Yesterday, I got home, gauge was pegged, got out, popped the hood and looked. Water slowly was returning to the overflow tank and everything seemed normal. I walked in the house, changed clothes, came back out in about 2 minutes, and there was steam pouring from the grill of the truck. Popped the hood and apparently the radiator blew a hole in the drivers side.

Sooooooo...what is the problem? Does anybody have any ideas? Like I say, the gauge shows overheating, but I forgot to mention that I've been carrying around one of those laser heat guns and have checked the truck often...no matter what the gauge says, the manifold at the thermostat and the return hose always read 190. The hose going from the radiator into the engine I think reads around 140. Is there any other way to tell if the truck is actually overheating? Was the radiator a problem, a sympton, or just a coincidence that it went out? I appreciate any help anybody can give me. Thanks in advance.

 

[LarryRB]

I lost a radiator at 40K miles on a Dakota. For me, it was plowing snow and evidently getting a lot of road salt in the lower radiator area. It prematurely blew out.. Anyway, I had your problem on an older Dodge., They have a paper thin circuit board behind all the gauges. Pull your gauge cluster and you can see this thin circuit board. You have to remove all the small night lights (they pop in and out) then remove that circuit board. It can be cracked, shorted or? You should be able to tell by looking at it very closely.

 

[RobertN]

Check your hoses. If they are soft, they can collapse and cause poor coolant flow. If it is aleardy warm, and then you take away the cooling by shutting off the engine, the the water inside the engine will heat even more for some time, hence the blow out you see.

Check the fan and clutch. If the clutch is going, it may not cool properly. Also, if the clutch is going, the fan may not spin properly, and can cause wear on the waterpump bearings.

When you replaced the coolant, and topped the system off, you used a 50/50 mix? Too much water in the mix, and it might boil over when the engine shuts off and the water in the engine really heats up.

What about the belt, condition and adjustment?

 

[getut]

Drive near the Dodge dealership.. staying close to them until it heats up... pull into their lot, shut it off, wait for it to start bubbling over and drag the service manager out by his upper lip. If he says nothing is wrong, hold his head really close to the bubbling liquid while in plain site of the heat gun still showing 190/forums/images/graemlins/grin.gif

 

[bgott]

First off, check your gauge. There is a gauge tester available that is basically a box with rheostats that you hook to the wire at the sender and a ground. You have to dig deep in the service manual to find out how many ohms you need to imput for low, medium and high readings on your gauge. Once you know that the gauge is reading right you need to install a new sender. You might not have the right thermistor for your application or the one you have can be bad. If you end up with the wrong one it will give you fits, I had a Chevy 454 powered motorhome give me fits one time because the sender for a pickup is NOT the same as the one in the MH. The pickup sender will read way too hot, the one for the MH is calibrated to read way cooler. I would also check the gauge panel and body grounds, bad grounds are the cause of most electrical problems. You also need to check and see if that model has an instrument panel voltage regulator, those wil also mess with your head. A wiring diagram will let you know exactly what you are dealing with as far as the type of system and what kind of goodies it has in it. Did the dealership check the temperature with a computer scan tool? I used to check that kind of stuff through the scan data, if the computer is seeing 190 degrees and the gauge reads 250 you know which way to look. On that model the computer should be the input for the gauge, I think. I'm a hair rusty. /forums/images/graemlins/tongue.gif In that case the sender is called a coolant temperature sensor and outputs to the computer. Once you are sure that the indicating system is right your problem should go away, unless the truck has leaking head gaskets or a cracked head. Other worse case coolant circulation problems include blockages from someone replacing freeze plugs and beating the old ones into the block or head instead of removing them and water pump impellers spinning on the shaft or having the fins rusted off. Since you keep getting a reading of 190 at the manifold every time you check it I'm going to presume you didn't install the thermostat backwards. You might, however, have gotten a bad thermostat right out of the box. Before I got out of bustin' wrenches for a living I was noticing more and more bad "new" parts. /forums/images/graemlins/mad.gif It really sucks when you install a new part and end up with the same problem, or worse, a different one. It was probably time for the radiator to blow, skip the dealer for that and go to Vatozone, they are a lot cheaper and the aftermarket radiators seem to at least equal OEM quality.

 

[Soundguy]

My 98 runs right at 200 on the gauge.. never gets hotter.. even when towing.. same 5.9l engine.

After some hard work, and aprking, I'll sometimes here a gurgle of water t/from the overflow.. but never any steam, or 'boiled-over' coolant.

I agree with the others.. something is wrong with the cooling system...

I was gonna say do a flow test on the radiator.. but looks like it is going to be repalced anyway now.. etc.

Soundguy

 

[rtimgray]

Here's an update on my story thus far (kind of Prince Valiant style, huh?):

Pulled the radiator yesterday. Took off the top and bottom hoses - noticed that the bottom hose had a spring in it. Actually, it was two springs - look like they are supposed to be there and wouldn't cause blockage. I'm planning on replacing both hoses anyway - they do feel a little soft. I replaced the sending unit for the gauge and conducted the test as outlined in the service hayne's manual. It just says, disconnect the wire and turn the ignition on. If the gauge rises to it's low setting, then the gauge is functional. Well, the needle moved a little, but not all the way to the low setting? So is the gauge or the sending unit bad-dunno. It has a new sending unit now, anyway. On this model, there are at least two water temp sending units. One (which I replaced) goes to the gauge. The other sends information to the computer so I guess they are parallel systems and don't necessarily get info from each other(?).

I'm also putting in a new thermostat - I'm getting that from the dealer. I had a real bad time with my 83 Nissan truck thermostat one time. Went through 2 from Autozone, 1 from NAPA and 1 from carquest and none of them worked (they always stayed open and truck wouldn't warm up. Went ahead and spent an extra $5 and bought one from the Nissan dealership and the problem went away (weird). I think that I have always installed them correctly (spring side on the inside, right?). I've got a new radiator coming from radiatorbarn.com - it's about $145.00 vs. $222.00 at Autozone.

Good tip about the too much water and boiling thing (I shoulda thought of that). I've had a little water leak (I think I found it at the thermostat - looks like it's been leaking there) and since it's warm, I've always just topped off with water. Maybe that's why it boiled over a few times. I'm still just curious if the truck is really overheating or not. I can't imagine that if it was really overheating (often the gauge shows to 240 or 250 and it doesn't boil over) and I've been driving it for most of the year that there are no ill effects. I'm sure you guys know that a hot engine usually seems to have a "smell" to it (at least to me it does), and this one, except when the coolant actually has boiled out of the overflow jug, hasn't smelled that way. Is there anyway that the coolant overheats put still reads 190 at the thermostat (that's not even boiling for water - but it is under pressure, sooo.....).

And by the way - I liked the idea about driving around the dealership til it starts to boil over and then grab the service manager - I wish I'd thought of that!

Plan from here - put on new sender, t-stat, hoses, radiator and fill with 50/50 coolant/water mix and see what happens. Thanks for the help and advice fellas. Take care.

 

[Egon]

The springs in the bottom hose are there to prevent the hose from collapsing.

Electronics may work well when cold but as they heat up problems can occur.

Egon

 

[rtimgray]

I figuered that's what the springs were for - it's just I've changed several hoses and never had seen that before. They pretty much had to be there on purpose though.

Good point about the hot/cold electronic thing. Thanks.

 

[Bird]

Those "springs" in radiator hoses used to be very common, but I don't think you see quite as many now as you used to. And of course, as has been said, they're just to keep the hose from collapsing.