Car over heating very fast under load...

[96Holly]

This post is also under the C4 general discussion forum

I figured this was a better spot for this question.

I have a '96 LT4 with a Mez elec water pump installed last year. (Rad also removed and cleaned) The car ran great for a couple mo last season and good a for a couple of runs this season. Then it over heated at an ATM for no apperent reason. I have replaced all three relays (replace with only 5 prong... 4 prong not availible anymore?), replace one fan motor (right side) and replaced fuse (fuse blew because of fan motot being bad... assumption)

Once installed I filled the system, started car with both the air bleed screw open and small hose located on upper right side of rad loose. It purged over a few times but no big deal (probably the air in the system) once warm it gushed then subsided then gushed etc. Shut it down, refilled system opened up screw all the way till a steady steam came out. I got some fluid at the small tube as well. Closed everything up let it idle to hear the fans kick on at the right times.

Took off down the road with a cold engine to have it over heat again about 1.5 miles from the house. By the time I got it home the analog gage was pegged (that went first when I was 1.5 miles from home... I turned around to go home) and the digital was also in the 250 range with the dash lite up with "check gages". Oil temps never reached that high only about 220. As well it was about 5min or less with the analog and digital gage ringing high.

I plan to hard wire the fans and pump for any issues. I don't think the pump is wired with reversed pority due to it running so good last season. I am thinking more mechanicall like the impeller coming loose from the shaft or ???

Why would it only overheat under load and not at idle? ANY ideas/comments would be appreciated. sorry for so long winded, I like details when I am asked a question.

 

[Robertwav1]

Geez.....Check the front under car and make sure no obstruction (like a plastic bag) in the mouth area. Might be getting enough push from the fans at an idle but not on the road if this is blocked. Thermostat? If it has one, change it. Hope you find it!

 

[Vettefan87]

Do you have any type of low coolant light on? Are you sure there isnt any air pockets in the system? Once it gets hot does it stay hot, or will it come back down to operating temp?

 

[vetteboy86]

Can you see the coolant circulating in the radiator when the cap is off? Have you verified this temperature reading with other guages?

 

[96Holly]

Thanks for the replies.

Robertwav1: That was one of the first things I did along with changing the therm. stat.

Vettefan87: No lights came for low coolent. As far as bubbles the first time it over heated it ran for about 2 mo last season and a couple of runs this season. Although I didn't know that if the temp got hot due to a bubble it will stay hot.

vetteboy86: After I bleed the air from the two locations I didn't open the system again. That would be a good thing to do to check for flow. The only two temp reading were from my dash but by the look of the boiling water flowing from my overflow tank I am assuming that ist WAY to HOT!!

After reading this maybe the first time it overheated was the fact that I did have a fan out and a blown fuse. Then the second time was just air bubbles in the system that didn't surface until I put the car under load. Thanks again for the replies.

If anybody else has any thoughts please chime in.

 

[Vettelt193]

first off, your car should run fine with only 1 of the 2 fans working (i know from experience.... I had a '93 that had only one fan working for about 2 years. the only time i had a problem is in traffic with the A/C on.)

First off, is the radiator even hot? i think this is a t-stat problem still... take the t-stat out for temporary use. does it still overheat? I am betting with the t-stat removed the car will run fine.

The reason why I think this is because it would take far longer for the car to overheat if all of the coolant is at least flowing through the engine... if only the block is keeping the car cool, it has plenty of coolant to keep it cool at idle, but not nearly enough when you put load on it.

if it still overheats, jump wires to the pump so you can run it with the car off. Run the car until it is hot (over 200) then shut it off, but keep the pump on. the temperature should drop pretty quickly... if it doesn't, you have a flow problem on the pump.

 

[96Holly]

first off, your car should run fine with only 1 of the 2 fans working......

Thanks. Because it heated up so fast I was thinking no flow as well, hence the idea of the impeller. It threw me about my fan being out though.... many things it could be....

Anyway thanks for the reply. I plan to work on her this weekend once the kids hit the hey....It will be a very late night for me this weekend!!!

Anymore is still appreciated.

 

[vetteboy86]

I would also suggest taking the T-stat out. You can check it as well, I did with mine. I boiled some water on the stove and used a thermometer in the water. Sounds kind of corny but gave me peace of mind.

 

[96Holly]

As I was working on Holly this weekend...

I was looking at my hoses. This problem could be my hoses as well. I wasn't able to fire her up this weekend but remember reading around that if a hose is weak it could collapse and stop the flow. My main hoses to and from the rad to the engine are new (not a guarentee but possible). However, if one of the smaller hoses from the filler tank is bad and callapsing could that create a "no flow" problem?

Should be able to fire her up this week. Lot's of rain here in SE Mich over the weekend. I have the pump hard wired and need to perm-a-seal the stat housing to the pump to run without the stat then fill it up. I will check the hoses when I get it up to temp.

ad .... dang rain.....

 

[vetteboy86]

With your car being a 96 I wouldnt think it could be a bad hose, although it wouldn't hurt to check.

good luck

craig

 

[WhalePirot]

Does your hose have an inner spring to prevent the collapse?

Have you moved your temperature sensor?

Read the various sections of this: http://www.madelectrical.com/index.shtml

 

[aquavette]

I have a 94 LT-1 /6 speed coupe.I was over heating and found my rad cap not on correctly....make sure to have the 2 arrows on the cap inline with the small hose entering the overflow tank........that solved my problem..Good luck

 

[WhalePirot]

You might test the radiator cap for proper pressure holding. They do get old and weak.

 

[Ken Anderson]

Your car is desingned to run cool without the fans being on unless the A/C is on or you are stopped in traffic. You need to forget about the fans, sensors, etc. until you run at normal temp while crusing.
That said, it would appear you're on the right track-poor or no coolant circulation. I would suspect the W/P has failed or you have blockage in your system. Keep us posted.........

 

[96Holly]

Thanks all...

Still raining here and now I am away on business. :cry Thanks for replies. I will keep you posted as I test it later this week or over the long weekend.

I don't have (or at least don't know if I do) spring loaded hoses. I bought them at Autozone if I remember correctly. I will check/replace the cap as well. Sounds like a weak link over time anyway.

 

[WhalePirot]

Squeeze the hoses and see how easily you collapse them. The lower hose has a spring inside. Neither should be real soft.

 

[96Holly]

Update...

Finally able to run my test. Hard wired the pump and removed the T-stat. After purging (more on that in a minute) I let it idle for about 20 minutes. It got up to only 218. No leaks, no problem with hoses clapsing, no problems. I shut it down and left the pump on. It didn't cool down much after 5 minutes (maybe 5 to 7 deg) so I thought lets go for a ride. It's kinda warm in the garage anyway...

During driving it cycled just fine, on the open road it cooled down very fast...10 to 20 deg pending on how long I drove at a constant low RPM speed. I drove about 20 minutes. Fans never had a chance to click on. Air temp was about a 75 deg with med/high humidity. Fairly warm ambient... I havn't tested the stat but I think overall it was a bubble problem. Here is why...

When you got an elec pump this thing runs full out all the time. Run it with the purge valve open and you are sucking air at idle.... .... turn the pump off and you can hear to bubbles running around the system. Purge and close off system and then drove it. Ran great. After running I let the pump continue and didn't hear the bubbles in the system.

I am still cautious about driving further from the house. A few more trips to the store and around town should calm my nerves. I plan to add a switch to cabin to switch between a hard wire system and a relay run pump.

Thanks all!!

 

[Vettelt193]

I like the idea of hard wiring it... especially if you throw a switch on one (or both) fans too. then you can cool down your car very quickly anytime you need to. Glad it is working ok for ya... good luck

 

[jmccloud]

Purging and burping

The '95 service manual (obviously for a stock type water pump) recommends cycling the temperature full up (drive for 20+ minutes) and full down (cool over night) before making any 'agreesive maneuvers' which must mean high revs. or load.
I changed the coolant last year and found that the temp was very erratic at first and became more stable with each temperature cycling. Each heat-up/cool-down sucked progressively less coolant from the expansion reservoir (the white one behind the right headlight).
This was after initially operating the engine with the bleed screw open until a lot of coolant ran out and air bubbles had stopped.
Good luck

 

[96Holly]

I think purging these things is tricky sometimes. I have purged the car with this elec pump a number of times with no problems. Not sure what went on this time... Shish!!!

I will repurge again just to be safe.

Thanks.