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Another 98 Grand Voyager Mystery Overheating Problem (HELP!!!)

25K views 21 replies 10 participants last post by  mistypotato 
#1 ·
I’ve been working on my sister-in-law’s 98 Plymouth Grand Voyager (3.3L) I have some experience with this engine as my 91 voyager has over 300K miles on it. The van is overheating (indicated), and I suspect it’s just an indication problem. My Autoxray scanner indicates temps as high as 260, but there is no sign in the engine compartment that anything is wrong (boiling over, smoke, fire etc …. I’ve tried everything, but nothing seems to make a difference. Thanks to all of you who have posted to other mystery overheating problem threads; I’ve tried all your ideas … still no love. Here are the actions I’ve taken to date:

1. Removed thermostat to see if it was stuck closed … no difference. Upper radiator hose is hot w/ or w/ out the T-stat installed.

2. Pulled and inspected the radiator; can’t see any problems with it. Water flow is good.

3. Pulled the water pump to see if the impeller was spinning on the shaft; no issues there either. But, I may be experiencing low flow due to the shabby aftermarket impeller design or wear or both. It's an aftermarket pump.

4. Changed all cooling system hoses (some were original equipment); refilled system with cap removed. T-stat opens at 195 deg F and it’s obvious water is flowing through the radiator.

5. Replaced fan relay module; fan’s were running backward. Fans are fine now and speed increases to 100% at coolant temp hits 230 (per the Chrysler spec sheet I downloaded).

6. Replaced the radiator cap; it was leaking. Changing the cap allowed me to drive a little farther than before (now that the cooling system can pressurize), but the temp gauge eventually went psycho. Had to turn the heaters on to drop the temp.

7. Changed out the temp sensor (was reading low resistance); no change.

8. Ran a compression check; the van has 207K miles, and compression values range from 89 to 103 psi. I’m not losing any water.

9. Performed a vacuum analysis. No issues there either.

Note: Coolant recovery tank level rises and falls as you would expect.

The one consistent thing I’ve seen is that all the other threads on this subject all fail to come to a conclusion where they mystery overheating problem is solved. Are there any other tests I can perform? Has anybody ever solved this type of problem? If so, what was the fix?
 
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#2 ·
Update: I've changed the water pump based on inputs from users on other threads. The screeching noise from the engine compartment is gone, but the temp gauge is still indicating it's too hot. Eng scanner is saying 230 deg F at idle with front and rear heaters running. One additional input, the temp really goes up when I go for a drive. I thought airflow throug the radiator would make the temp go down, but not in this case.
 
#3 ·
The Latest:

I put the T-stat back in the van, and ran the engine with the radiator cap off and a temp gauge in the filler neck of the radiator. I also had my Autoxray scanner connected to monitor eng temp. Once water started flowing (T-stat open) The scanner indicated 230 degrees, but the temp gauge in the filler neck indicated 140. Granted were measuring temperature of the water in the intake manifold as compared to the “cool side” of the radiator. Yes the temp gauge indicates 212 in the pan of boiling water. While I was watching the temp of the gauge in the filler neck, I noticed the water level in the radiator was rising and falling. This is normal as the thermostat opens and closes, but in order for the T-stat to close (even partially), the temp has to drop below 195. So, the water level was rising and falling while the scanner indicates 230. At this point I think it’s safe to say this is strictly an indication problem.

I’ve check resistance between the disconnect and the temp sensor and it reads .5 ohms, but I haven't checked for shorts to ground yet. Does anyone know what the pin connections are for the temp sensor at the 60-way connector?

OBTW, the scanner indicates temp sensor at 1.6 volts @ 230 degrees.
 
#4 ·
I suggest you try one other thing, remove the radiator cap with the engine cooled down. Start the engine, let it warm up and have an assistant stuff a shop rag over the end of the exhaust pipe to create some backpressure. Watch for bubbles in the coolant, which would indicate exhaust gases entering the system (possible cracked head??). If you see no evidence of bubbling, I agree with you it's likely an instrument/sensor issue. 230 F is what I would consider normal under 12 to 15 psi pressure.

When you drive it in the "overheated" state, does it ping and act like an overheated engine? Does it run on or diesel when you shut it off? If not, I question if you really have an overheated motor.

Like me, you're replying to your own posts. But you're giving good information. Hopefully someone else will chime in here with other ideas.
 
#5 ·
Thanks for the suggestion, but I'm thinking if I did have an internal problem with the engine it would have showed up during the compression check, the vacuum check, and I'd be losing coolant. The van drives normally even when the needle between 3/4 and max (and I have to turn on the heaters) ... no pinging or dieseling. I'll be taking it to the dealer today to have them diagnose the temp gauge. I'll make sure to post what they find out.
 
#6 · (Edited)
Sounds like the radiator isn't doing its job since using the front/rear heaters will cool it down. Thermostat should be keeping the temperature uniform when not in an overheating state. The fact that driving makes it worse indicates the heat exchange at the radiator is lower than it should be when the engine is working harder and in need of more cooling.
You have done a lot of work and provided great information.
PS:
The top hose should feel noticeably hotter than the bottom return hose when working properly.
Has "stop leak" been added to the radiator at some time? Too much of that type of product will affect flow in the radiator.
 
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#7 ·
Thanks Jeepman, and I would tend to agree with you except I've pulled the radiator and put a hose in the stub where the lower hose from the water pump attaches. Water flow very easily through the radiator, and from what I can see by looking down the filler neck, the thing looks brand new ... no signs of corrosion or debris. Don't know if my brother-in-law ever put stop leak in the system, but I'll check. Yes the top hose is noticeably hotter.

I started shooting wires last night. The blk/blue (ground wire) checks good (.5 ohms), but I'm reading 15K ohms from the tan/black wire back to the ECU. The Haynes manual has the schematic, but it doesn't list what the values should be between the sensor and the ECU. While driving the van to the dealer this AM (in order to turn this diagnosis nightmare over to them), the temp gauge was right in the middle. I was thinking that by pulling the harnesses apart to check resistance values and then putting them back together, I may have "reseated" a bad connection. But the smile on my face was gone as soon as I turned on the AC; the temp shot up rapidly. I had to turn the heat on to keep the needle off the "H". At certain points the needle hit the white line right next to the "H", but the van never acted or smelled like it was hot, and the recoery tank level was at the normal level for an engine at temperature.

The dealership is booked for the next 2 days, but I should hear something from them by Friday. I love a good mystery, but this one is killing me.
 
#8 ·
If radiator fins are in good shape, then it's likely the gage giving wrong readings as you suspected.
 
#11 ·
Did you put the wrong type of coolant in? I personally have only worked on my BMW's cooling system but I know GM has something with Dexron and orange and green **** that you're not suppose to mix. Additionally I have seen on more than one occasion somebody buying full strength coolant and thinking they can just pour it into the reservoir.

I am NOT insulting your intelligence bro! But you covered the basics so I can't see too many other explanations.
 
#12 ·
Mystery solved! I took the van to the dealership; after 3 days, they couldn’t find anything wrong with the radiator, cooling system components, or the indicating system, and suggested there is something wrong with the cylinder heads or the block. So, I went back to the forum to see what responses I received.

Special thanks to Jeepman and Imahokie! I purchased a new radiator and pulled the old one. Even before I put the new one in, I grabbed my slip-joint plyers and pulled the end tank off to check that baffle. Sure as S#!t, the baffle was gone. With the baffle gone, hot water entering the radiator is allowed to flow directly back to “pump suction” without having to pass throught the radiator cooling fins. With the baffle in, water has to flow from right to left (drivers’ perspective), across the top half of the radiator, then down, and then back from left to right across the bottom half of the radiator to get to the water pump inlet. I’ve attached a picture of the inside of the radiator end tank.

 
#13 ·
What was the brand of the defective radiator and where did you buy it?
I might have to replace mine (there's a bad leak and I must first find where it's from) and I do not want one with a baffle that will fail.

Thanks

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#14 ·
I have had 2 aftermarket radiators fail this way so far. Luckily I buy them from a place that offers a lifetime warranty, but it is a bit of a hassle to keep replacing them. The original one lasted 10 years. I think it's a bad design coupled with poor quality aftermarket parts.
 
#15 ·
FYI, the radiator that failed on me was purchased at Performance Radiator. They have locations around the country (and online). They did not honor their 3-year warrantee (it failed after only one year).
After this experience, I'll only buy a radiator from a supplier with a good lifetime warrantee. Lesson learned...
 
#22 ·
I know this is an older thread but for the benefit of others...let me 2nd the advice to steer clear of Made in China AutoZone radiators. They are very poor quality.

I ordered one off ebay 4 years earlier and it is so much better I'm considering putting the old one back in.

I feel very taken by AutoZone on this item. Of course, once installed, no return. Just warranty.....but I don't want to put another junk radiator like this on MY car.
 
#17 ·
I think I'm having the same issue. The std radiator has both hoses on the same side. I thought that was unusual. I can put a coat hanger straight thru and also took a mirror and don't see any baffle. Its an aftermarket radiator about 3 yrs old. I think I am going to get the HD radiator that has a long lower hose and outlet on opposite side. I think this is a design flaw from Mopar as the 2001 and up radiators have hoses on opposite sides.
 
#20 · (Edited)
Baffling for sure!! :)

Good to see you got it fixed. Hoses being on the same side shouldn't be a problem if the radiator directs the flow properly via baffles/whatever. Radiators with hoses on opposite sides also have a problem if the baffles aren't in place, i.e. the coolant goes in and directly out to the other side. I think the problem is with the aftermarket, not Chrysler.
 
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