JamDeeper

Okay. I may have let thus go for too long but I need to figure out my best options.

Symptoms:
rusty antifreeze
Cool air blows when heater is on.
Overheats after 20 miles or so
Once cooled (after sitting for 30 min) to normal temp, thermostat doesn't open again.

When I start driving it, the temp seems to be fine. I can watch the gauge drop when the thermostat opens 2 or 3 times, but once it gets past 210, it's like the thermostat doesn't open anymore and almost red lines before I stop to let it cool. But the thermostat doesn't open still. It seems to only open when I first start driving (first time for the day)

A few months ago I flushed the system 2 or 3 times and refilled with 50/50 premixed and burped it through the rear temp sending plug on top of the head. After driving it the past couple days, it's already rusty again. And I mean RUSTY.

Put in a new thermostat yesterday along with a new overflow cap (garbage things)

When it overheats it sprays out of the overflow cap.

My question is... where do I begin? Should I just overhaul the whole cooling system? Rad, hoses, overflow, core?? I can't drive 20 minutes without it acting up and having to sit in a parking lot till it cools.

Hope I can get some input. Thanks

JamDeeper

89 4.0L l6 5 speed

timberwolf

The heater core may have been plugged and the flushing loosened some of the rusty crap that is now messing with the thermostat

Disconnect the heater hoses and see if you can flush the core completely

JamDeeper

I have just finished flushing 3 more times. Block, core, and rad. I can't believe how disgusting it is. Finally got clear water out of it. Would the rusty shi% not cool as good as clean antifreeze? Even still, I don't know why my thermostat would stop opening.

DFlintstone

Water actually cools better than antifreeze, also boils at a lower temp. Disconnecting the lower rad hose will let you flush larger pieces of crud then the drain. I'm curious how you know weather or not the t-stat is opening. Not allot of help here, wondering if there is enough crud to plug things up somewhere.

Can you post a pic of that "overflow" cap?

Two minute Head Gasket test.
A quick head gasket check. Preferably with it warmed up; remove the cap, fill it to the brim, and power-brake it with the cap off. Do be careful. In drive, pressing on the gas, of course something could go really wrong. Your foot is firm on the brake, and no-one is in front of the Jeep! Give it medium throttle and watch the coolant at the filler. If the head gasket is really shot it will bubble, or even geyser out the filler as combustion gasses shoot past the gasket into the water jacket. This won't tell you it's OK, but it can be pretty clear if its bad. Sometimes some surging is normal. If it just comes up a little or spills a little you may still be OK.

JamDeeper

Ya I've been using the lower and upper rad hose to flush the rad. With it being a closed system, I cannot take the cap off. At least I won't attempt it while it's hot.

And I belive it's the thermostat opening, because I'll sit at 210 degrees for a sec and then it will drop (like cooler water is being let in) anything else cause that? It will do it about 3 times, regulating the temp. Then just stop, and get hot.

Here is my $6 cap from auto zone. I know these things are tempermental, but thought I'd try any and all things known to be crap in these renix systems.

DFlintstone

I have no gauge, but I noticed something like that testing my temp sensor.
Don't know, but I wouldn't expect the T-stat to start failing closed, then repeat that next time.

I might try that power/brake test and take it from there. An engine will get hot right now if any 2000* gasses are making it into the water jacket. Not saying that's likely, just might be easy to see if it's bad.

Belt is tight, voltage stays steady while the temp is fluctuating?

Btw, the Renix cap also has a pressure relief...

JamDeeper

Belt is tight, volts are at 14, drop to 13 when the aux fan kicks on. This cap is also a relief cap, 16lbs. Its just odd to me that everything seems to be working (all coolant hoses are hot) I just don't have a heater and I over heat. I'll try that test and see what I get. I don't think the gasket is bad. Runs like a top, hot or not. Oil is clean.

cruiser54

Your new cap leaks when it gets to 210?

703-1396 is for the Volvo replacement cap that works 10 times better than the cheap chinese ones. I'd try that next. Even new replacement standard caps don't seal well on older bottles. The Volvo ones do. No seal=overheat.

RTorrez1

It sounds like you have neglected the cooling system for to long and now it's biting you in the A$$. I would start by adding some cooling system flush and try flushing each component (Block,Radiator,Heater core) separately. You may have to do it several times to get all of crud out. With a little luck you didn't let it get to bad that all you have is rust holding everything together. If so then it will be almost imposable to get the rust out.

DFlintstone

I've been puzzling over (our), temp. fluctuations, and your ultimate overheat. Gonna go out on a limb with an idea. People have posted photos of their pump impellers corroded to just flat disks. On the way there they get weaker, and weaker. Hot and cold water will try to stratify into separate layers. I wonder if a lazy flow couldn't cause the fluctuation. As the t-stat opens, not enough comes through to cool it, so it continues to open. By the time enough of the coolant makes it, the t-stat is to far open, and closes as to much comes in. Repeats. If your impeller is corroded enough, the hot and cold may end up stratifying, stopping all flow when it gets hot enough, then you overheat. Cold, even a very weak pump can circulate it. Pretty goofy I know, but a thought. An IR temp gun measurement high up, and low down might reveal something.

Was a head sctatcher for me when I saw my numbers fluctuating/cycleing while checking my CTS. I had thought the T-stat would keep it at a steady temp. My pump is about 10 years old, maybe I have something like that going on myself.

In any case, checking/changing your water pump seems to make sense.

JamDeeper

I will keep you posted. I may do it this weekend. My pump is only 3 or so years old. I'm not too set on that being the issue, but it's worth a shot, and not too difficult to do. I also need to get the BMW cap.. I noticed a Crack in that new one I just bought. *sigh* we'll see how it goes.

JamDeeper

*Volvo cap.*****

DFlintstone

Napa 703-1396 Is the Volvo cap Cruiser is so exited about. In my case it leaked, unless I really cranked it on there, then it cracked.

I can only assume something is different with my bottle. I put the stock back and it"s OK though.

Pump is only 3 years eh. Agreed...really rusty ugly coolant though...Maybe see if you can pick up a gasket when you get a cap, try the cap..., take it from there.

Mine will run un-pressurized, (with 50/50) without boiling. Each time I crack a bottle I run that way for a bit till I get a replacement. Now that I'm clear on always leaving it 1/2 empty I haven't cracked one.

Bobolink

I think your stat probably works okay, it's just that the rest of the cooling system is shot. Sounds like you have about 1/2 a radiator at most, with all the tubes in the lower half completely blocked with rust or whatever, and same with the heater core. Once the engine is truly warmed up, stat wide open, the system still fails to keep the temps down. When you let it cool back down to "normal," the stat is still wide open, but the radiator isn't doing it's job, and it goes to red line almost immediately, even though the stat is open. I'd be willing to bet that if you completely removed the stat as a test, that the engine would still overheat. At least then you would eliminate the stat as one culprit.