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View Full Version : Wierd overheating problem.


Baka420
- October 1st, 2009, 02:37 PM
I posted this on the 3si forums already. Then read in the STL section that a lot of you guys prefer to post here. So I figured it couldn't hurt to post here too.
Also if anyone knows why I can't get into the STL section, even after registering to the group, please let me know.

Sorry in advance for the long post. I just feel it relevant to give all the information I have, in hopes of finding a solution.

The main issue. The car will run fine for a long period of time, then start to get hotter and hotter until it overheats.

So to start it is a 1991 Dodge Stealth SOHC. I bought this car in July. The car was for sale about 2 1/2 hours away, about an hour outside of Saint Louis. I drove the car home after buying it. I ran it hard, wanting to test it out. Went a good 15 20 miles at 100+ then rolled 80 the rest of the way. No issues, gauges were all good. I got it home and changed the plugs, wires, cap, rotor, belts, oil, and antifreeze. The antifreeze was a rusty green color, the nastiest antifreeze I have ever seen. I drive this car as my daily driver. Over the first week I stayed local, to work and back, etc. Car ran great no issues what so ever. I live in a rural area so everything is highway speeds, 55+.

After about a week I took it out on the road to Kansas City, about 2 1/2 hours from here. The car ran great for the first half of the trip. Then the temp gauge started to climb, then fall, then climb, then fall. This was not a gradual thing either, the needle was moving quickly up and down. All the time staying within range. All my other gauges were good, no lights. Just a temp gauge doing something I have never seen before. I continued to drive and it kept doing the same thing. Except it was getting progressively higher. I stopped and opened the hood. I could hear gurgling in the reseviour. Other than that no signs of too much heat. No weird smells or anything. I drove it the rest of the way to KC and it was fine. Temp stayed put. All was well. On the way home it was fine until about 3/4 the way home. Then it started with the same thing.

After getting home I changed the thermostat, I kept the car in town for a few months after that with no issues. Then one day I took it on a longer drive, I'd say about 45 miles, and by the time I got home it was just starting the surging. I took it to a mechanic who saw a few unhooked vacuum lines. He plugged the vacuum system at the throttle body and said that could very well cause the surging.

I needed to test this so I took it to Springfield, MO, about 75 miles away. The car ran fine for the first hour then started to surge. I was mad at this point and pushed the car. Took it over 100 and the temp seemed to fall, but continued to go up and down. I got in town and was sitting at stoplights with no issues temp stayed put. None the less I was baffled. On the way back same thing. At this point I have checked everything and all seemed fine. So I just let it go. Bad idea...

I stopped about 10 miles short of my home and checked everything. Oil, coolant, everything. All was well. I noticed the temp gauge was about pegged when I got back in the car, started it and it dropped a bit. I got home and looked at everything while it was running and noticed thick white humid smoke coming out of the exhaust, along with a lot of water. My coolant was about empty. Only 1 gallon or so was in it when I drained it. Knowing full well I blew a head gasket, cracked a head, or cracked my block, I tore into the motor.

Over the next few days I got everything apart. The head gaskets were fine. I took the heads to a machine shop and the checked to see if they were warped, they were not, but one was cracked between the valves. I ordered another head. While putting everything back together I checked out the water pump. It looked like it had been changed recently, along with the timing belt and the head gaskets. I put everything back together, with the new head, and got the car running again. All seemed well, no white smoke. Coolant levels were good. I fixed it

So I drove it in town for a few days and all was well. I then took it on a trip a little over 100 miles. Car ran great, and I ran it hard. I'm on top of the world at this point. Pulling on to my road at home I look down and $%*& me I see the temp rise and fall. So I parked and watched it do the same exact thing for a few minutes. Shut the car off and let it sit. About 30 mins later went and drove it a good 40 miles and the temp did not budge.

I am at a loss here. The water pump looked excellent, I drained, pulled and flushed the radiator. The flow through the radiator was strong. The antifreeze was discolored a little, pretty sure its because of all the residue crap that was in there.

Again I am sorry for this epic post. Just want you guys to know all the facts before helping me diagnose.

xwire
- October 2nd, 2009, 05:22 AM
I would be putting another gauge on it so you can actually see what it is doing, I do not trust the 20 year old factory gauges when it comes to trouble shooting

Baka420
- October 2nd, 2009, 09:05 AM
I can understand that, but this gauge has given me no reason to doubt it. When I did doubt it, I cracked my head. The last thing I want to do is start spending money on things that MAY help the issue. That aside, new gauges were on my list of eventual upgrades, just not sure I'm going to be upgrading anything if I can't get this issue solved.

P.S.
Xwire, I want to have sex with your red 3000gt!!! Beautiful car.

whitedragon
- October 2nd, 2009, 09:37 AM
I can understand that, but this gauge has given me no reason to doubt it.

xwire is saying that you need a reliable gage to tell you what your temps are actually doing. By the time your old factory gage pegs hot, it could be too late as it could have already been hot a while before the gage registers. This is not an "upgrade" but rather a valuable troubleshooting tool. If you don't know how hot it really is getting, you don't know if you have a problem or not. Your gage could also be off, reading normal when in reality you are 20+ degrees hot and slowly causing damage that you don't notice.

The first rule of troubleshooting is to have reliable standards/measuring devices.

Next would be to check your thermostat I guess, but don't just throw parts at it, measure what it's doing so that you can accurately fix it. You'll save yourself alot of money in the long run.

Baka420
- October 2nd, 2009, 09:44 AM
I was looking at Oreillys for gauges and their are a bunch that range from $13 to $85. Will any temp. gauge that reads an actual temp. suffice? I'd prefer it to be as close to plug and go as possible. Also once I get it installed and take it for a test drive, what temps. should I be shooting for, and at roughly what temp. will I start getting into trouble. The thermostat has also been changed within the last month.

vr4gto
- October 2nd, 2009, 10:48 AM
if you want reliable but not expensive, pick up an autometer gauge

xwire
- October 3rd, 2009, 08:53 AM
any gauge that will actually give you a reading will do fine, I would not worry about getting a high dollar gauge or installing it perminate, just something so you can see what the engine is doing when the temps fluctuate

the factory gauge is buffered where it should not move from an engine temp of 190-210 it will just stay on the halfway mark

I would also be looking for a possible restriction in your radiator, cavation from the water pump, man there are a lot of possibilities

lets start with the gauge and it will give us some more options

Baka420
- October 5th, 2009, 09:28 AM
I am going to pick up a gauge tomorrow and install it. Over the next few days I will log temps and post them. I will not have time to go on a long enough drive to get it to start its surging problem as I am stuck at work all week. So that will have to wait until this weekend. Thanks for the help so far!!

whitedragon
- October 6th, 2009, 06:46 AM
cavation

Cavitation. Good word dude! Even an engineer would be proud. :squint:

xwire
- October 6th, 2009, 07:07 AM
Cavitation. Good word dude! Even an engineer would be proud. :squint:

no one ever said that my spelling was top notch... remember I just work on cars for a living, not write the manuals to fix them ;)

Baka420
- October 6th, 2009, 08:24 AM
I got a gauge and am reading the install instructions. It says that if my original temp. sending unit was used by a computer to control engine functions than do not replace it. Is this the case with my car?? If it is can anyone recommend a alternative place to put the new sending unit??

Baka420
- October 6th, 2009, 09:04 AM
I answered one of my own questions, the factory sending unit is needed so the fans will turn on, duh.. So any suggestions on where I install this aftermarket sending unit?

95gto
- October 6th, 2009, 09:28 AM
I answered one of my own questions, the factory sending unit is needed so the fans will turn on, duh.. So any suggestions on where I install this aftermarket sending unit?

our cars come with two senders stock, one if for the ecu and the other is for the gauge in the dash. Remove the sender for the gauge and replace it with the new sender. This way you have a stock location for your new sender and the ecu still has its sensor in place.

Baka420
- October 6th, 2009, 09:53 AM
Ok I found the gauge sensor, but there is no way the aftermarket one will fit in there. I also found 2 other sensors right there, assuming one is for the ECU, what is the other one for?? Both of the other sensor locations are a size that is able to accommodate the aftermarket sensor.

http://img205.imageshack.us/img205/9255/photo0180s.jpg
http://img21.imageshack.us/img21/7936/photo0181p.jpg

xwire
- October 6th, 2009, 10:13 AM
the AC over temp sensor

Baka420
- October 6th, 2009, 10:16 AM
Is that the one top of the theromstat or the one next to the gauge sensor. Also since I have no A/C compressor, condenser, or lines, couldn't I just use that for my aftermarket location?? If not looks like I will have to take this gauge back and get a new one with a much smaller temp sensor.

Thanks guys!!

95gto
- October 6th, 2009, 11:25 AM
Is that the one top of the theromstat or the one next to the gauge sensor. Also since I have no A/C compressor, condenser, or lines, couldn't I just use that for my aftermarket location?? If not looks like I will have to take this gauge back and get a new one with a much smaller temp sensor.

Thanks guys!!

Here is a link to a good walkthrough with some pictures:
http://www.supercar-engineering.com/rubberducky/3S/Mods/All/DefiWT/index.html

A couple of notes from my own personal install are:
1) you don't need to drain the coolant if you leave the radiator cap on
2) you may not need an adaptor for the sending unit, it will just depend upon your new gauges sending unit size.

Baka420
- October 6th, 2009, 02:19 PM
Thanks for the guide for install. Mine however is a SOHC engine. I used the location of the sensor above the thermostat. I believe this may have been the one that controls my engine being the fan no longer comes on unless I push the A/C button. However the temp readings I am getting at idle are around 190F. After turning the car off it climbs to around 210F. What kind of temps are ideal?? How high is too high??

Baka420
- October 6th, 2009, 03:35 PM
So upon further testing the fan still kicks on as it should. It does this around 200-210F and thats about where it stayed while at 3.5k RPM for 15 mins after warming up. If I turn on the second fan as well the temp will drop to about 190F. This has all been done at a standstill, nothing out on the road yet. I'm hoping those are good temps. as the factory gauge did not budge from normal. My big concern before I get it out on the road is the temp at which bad things happen :P

from sevastopol
- February 5th, 2010, 08:27 AM
Hello. My stealth was doing the same thing. So I just took out thermostat and never had overheating problem again. The heat still works