Cooling system testing??

OK fellas...I'm officially desperate.

Still struggling with cooling system FUBAR. When engine heats up and t-stat (new 195 stant) opens it starts blowing coolant out the overflow at idle OR at RPM's. ALL the cooling components are less than 3K miles or newer. 2 row CSF all metal radiator...1988 4.0L converted to open system...3K miles ago. I don't have a heater valve, I deleted it when I did the conversion. I know you've heard this all before, but I can't drive my truck anywhere without it getting HOT and blowing coolant. WTH??


I have tested:

• New catalytic converter, new exhaust manifold, new gasket & flange donut.
• compression - good (great actually) 119-124 within 5 psi across the board. No adjacent discrepancies.
• No water in oil, no oil in water
• NO driveability issues. Idles smooth at ~700-800
• exhaust gases (block tester) - none - tested it 4 times, with different fluid each time
• heater core - clear - no rust, crud, junk or small animals
• radiator pressure - holds pressure at 20 psi overnight - good, no leaks.
• cap - new 16 lb. - holds pressure @16 lbs for a couple of hours (the longest I've let it go)
• ZJ HD fan clutch
• all hoses - no leaks - spring in lower hose
• coolant QUALTY...it's new, and it's fine. 50/50 Prestone Green (ethelyne glycol) and distilled water.
• air bled from system...4 or 5 times and each time I have had to replace coolant.

How do I test for a.) a bad pump (it's not leaking, wobbling and the belt is good AND yes it's a reverse rotation with the belt routed properly) or b.) a blocked radiator before I drop the $$ on either. OR is there something else I am STILL overlooking???

Help me Obi-Wan Kenobi...you're my only hope.

Ok.

Another stab at this.

When the thermostat opens, at 195 F, the coolant is NOT boiling, right? Water at 212 F, 50/50 mix with a 15 lb cap 265 F.

So--what does that mean?

Well, it is SLOPPY, but the only way (without special tools) you can tell if the pump is pumping is to pull the top radiator hose and run the engine OR remove the outlet hose for the heater and check the flow there.

Now--the last time I had the head off my 90 she was a real bad girl to burp.

Did you drill a hole in the thermostat flange to facilitate air passage? If not, do that and place the holes at 6 and 12 o'clock.

Next, find a steep hill or a rock you can put the vehicle on, angled so that the front of the engine bay is up hill, and the radiator cap at the highest point. Run the engine with the cap off and let the old girl belch and burp all the air out, no matter how much coolant she spits out--when she is spitting she is purging air. Top off the coolant and see what happens.

I wish I was there to give you a hand.

I always drill a new stat 1/8" hole, 6:00 and 12:00

Took off heater hose, good solid flow. Gushing at first, then just a solid flow, til I replenished WATER then back to gushing. Emptied the radiator again, back to normal flow. I would guess the water pump is working.

Next.

Up in the driveway...on ramps. Rad cap definitely highest point. Let it run for 10-15 minutes as it bubbled a lot at first, then a little, then it belched water for a bit. I poured in some more water, it spit it out, repeat, spit and so on. The whole time it never got past 200F

I let it bubble out some more, lots of air coming out AND pushing essentially most if not all the water out as well, I turned it off. I added about 1 1/2 gallons of water back in. It topped off, and slowly continued to drain down. Total I added almost 2 gals of water.

I put the cap back on, fired it up. Remember it's all just water now, so the temp rose to 200F + and it started bubbling in to the overflow...same old same old. No change.

I shut it down, it continued to bubble in to the overflow. I flipped the neighbors off, came in the house, opened up a beer. Kicked the dog, yelled at my wife. Then I called all four of my kids individually and yelled at them too!! @$#&% it!!

FOR SALE 1988 Jeep MJ 4.0L P.O.S 187K miles
Runs great, five minutes at a time!! Make offer or trade for WORKING truck!!!

You need to get one of these,,,Lisle Cooling System Spill-Free Funnel Kits..
teamCherokee has them.probably NAPA too.

You can fill&burp and cool down with the funnel in place and no air entering the system.
When you drain the rad,do you use the "pull lower hose"method or the rad drain ? will any water poured in go right out the drain ?

Yelling at the wife...that,ll get you in Hot water.

once it gets hot shut it down and pull the e-fan out, put your hand on the radiator in various places and feel for a spot that feels cooler than the rest of it. I've had old gunk foul a new radiator before. if you find a cold spot put a hose with good water pressure in the bottom outlet and pull the top hose, flush it backwards with as much pressure as you can then put it back together and try again.

good luck, cooling system problems suck!

Wayne Sihler said:

You need to get one of these,,,Lisle Cooling System Spill-Free Funnel Kits..
teamCherokee has them.probably NAPA too.

You can fill&burp and cool down with the funnel in place and no air entering the system.
When you drain the rad,do you use the "pull lower hose"method or the rad drain ? will any water poured in go right out the drain ?

Yelling at the wife...that,ll get you in Hot water.

Click to expand...

I have generally pulled the hose, but when I did the last flush I did the whole thing, block plug, radiator drain AND the hose. Back flushed everything. I was very careful with the petcock, and replaced the block drain with a brass, hex head plug.

I'm fairly set against spending another dime for testers, kits and/or gadgets until I sort this all out. Just good ol' diagnostics...I'm a cheap mutha.

P.S. Disclaimer: I did not actually kick any small animals or raise my voice to any family members, or make any rude hand gestures to my neighbors...I did pop a brewski at 10:30 AM though and cursed bitterly.

GrimmJeeper said:

once it gets hot shut it down and pull the e-fan out, put your hand on the radiator in various places and feel for a spot that feels cooler than the rest of it. I've had old gunk foul a new radiator before. if you find a cold spot put a hose with good water pressure in the bottom outlet and pull the top hose, flush it backwards with as much pressure as you can then put it back together and try again.

good luck, cooling system problems suck!

Click to expand...

My XJ, about 4-5 yrs ago, had some sort of sediment in it, brand new, same make, CSF 2 row radiator. Looked like a handful of black sand. So this IS a possibility.

This is one thing I have not done. I don't know about using my hand as a temp seeker but I CAN borrow an IR gun. Still can't explain how so much air could be in the system without at least a tiny leak in the head gasket, and how an exhaust gas test would come up negative, 4 times, IF there was a leak. That's the puzzler.

Use the temp gun and shoot the radiator veins and check for cold spots. Also after driving if you have an automatic transmission shoot the tranny lines and get a temp reading. Finally check the the thermostat housing and verify the coolant temp sensor readings are accurate.

I know it sounds simple, but my coolant recovery bottle fluctuates at least a pint and sometimes closer to two pints between hot and cold. Is your recovery bottle big enough?

I always use dot laugh when one of buddies would come over with iis old closed system spewing. And usually found out he filled the surge canister all the way to the top. You need some room for expansion.

Just for the heck of it, try routing your heater feed just between the thermostat housing and the pump and see what happens.

I had a buddy who was shaving constant over heating problems and found out the thermostat housing gasket was shutting off the bypass. That bypass keeps a true temperature near the thermostat. A related problem in my 88 was when my heater valve got plugged up. my temperature would fluctuate between 240 (and possible spew) to 160. The thermostat would either open or close but it wouldn't regulate very well at all.

Just an idea.

When my radiator was plugged, my top radiator hose would be way harder than normal.

Just for the heck of it, push a small drill bit through the overflow nipple near the pressure cap on your radiator, seen it twice now, the inside of the nipple is plugged (or partially) with paint or casting flaw. This doesn't sound like your issue, but we seem to be grasping t straws here and running out of possibilities.

jsolorza said:

Use the temp gun and shoot the radiator veins and check for cold spots. Also after driving if you have an automatic transmission shoot the tranny lines and get a temp reading. Finally check the the thermostat housing and verify the coolant temp sensor readings are accurate.

Click to expand...

Tranny has a temp gauge on the return line, never over 160 so far, yesterday the IR gun shows 125 at the cooler 120 at the pan.

IR gun AND my hand (youch!) show fairly consistent temps all the way across the radiator, hotter at the inlet, cooler at the outlet,197 at the t-stat, all expected temps.

Have you made sure the cap fits and seals on the radiator properly? I got a new rad out of the box one time where the raised sealing ring inside the neck was improperly formed and wouldn't allow the cap gasket to make a good seal.
Also, what application did you use to choose your rad cap? A 95 dodge pickup uses 16psi and has the correct depth to seal in the neck.

8Mud said:

I know it sounds simple, but my coolant recovery bottle fluctuates at least a pint and sometimes closer to two pints between hot and cold. Is your recovery bottle big enough?

Click to expand...

Yes, I have an extra large overflow with good solid hose connection, I have been starting it, running it to temp, letting it bubble, level rises - then turning it off and letting it cool...just to see if I can purge any air "automatically". The level in the overflow drops when it's cool and when I open the radiator...it's full. So then I add more coolant (water at this point) and the motor does suck it back in.

8Mud said:

Just for the heck of it, try routing your heater feed just between the thermostat housing and the pump and see what happens.

Click to expand...

Do you mean take the heater core out of the loop?

8Mud said:

When my radiator was plugged, my top radiator hose would be way harder than normal.

Click to expand...

My heater hoses are firm and hot (but squeezable). My top rad hose IS hard as a rock (NOT squeezable). I really do not remember it being that hard before. Like it took a whole bottle of Viagra.
...and if I had some evidence that the radiator was the culprit, I'd replace it in a heartbeat.

8Mud said:

... but we seem to be grasping at straws here and running out of possibilities.

Click to expand...

Yes, grasping at straws is right. After doing the "normal" everyday diagnosing and hitting walls, it makes me WANT to find some glaring symptom that would point me in the right direction. I'm learning a lot from everyone's experience and input.

Thank You

Digger87xj said:

Have you made sure the cap fits and seals on the radiator properly? I got a new rad out of the box one time where the raised sealing ring inside the neck was improperly formed and wouldn't allow the cap gasket to make a good seal.
Also, what application did you use to choose your rad cap? A 95 dodge pickup uses 16psi and has the correct depth to seal in the neck.

Click to expand...

I wondered about this too. The "raised" part of the opening seems pretty flat. But it seems that the cap itself would leak (externally) instead of just allowing pressure to release "internally". I'll have to look at a new radiator and see what it.

I had the guy at NAPA cross reference the cap for the Jeep/CSF radiator...the guys at AZone...could not figure it out.

There are 2 sealing surfaces on a rad/cap... an inner, the main sealing point that holds the pressure, and the outer, that directs the released pressure into the bottle. If the inner seal surface is not right, or the cap cannot put proper spring pressure against it,(because it is too short) it will release too soon.

ParadiseXJ said:

Yes, I have an extra large overflow with good solid hose connection, I have been starting it, running it to temp, letting it bubble, level rises - then turning it off and letting it cool...just to see if I can purge any air "automatically". The level in the overflow drops when it's cool and when I open the radiator...it's full. So then I add more coolant (water at this point) and the motor does suck it back in.



Do you mean take the heater core out of the loop?



My heater hoses are firm and hot (but squeezable). My top rad hose IS hard as a rock (NOT squeezable). I really do not remember it being that hard before. Like it took a whole bottle of Viagra.
...and if I had some evidence that the radiator was the culprit, I'd replace it in a heartbeat.



Yes, grasping at straws is right. After doing the "normal" everyday diagnosing and hitting walls, it makes me WANT to find some glaring symptom that would point me in the right direction. I'm learning a lot from everyone's experience and input.

Thank You

Click to expand...

I was thinking, "What is different?" and the heater replumbing seems like one thing. If you make a loop and bypass the heater connections you've eliminated that as a possibility. Just for a test. I've been thinking that heater valve eliminator might not be a good idea for the early models anyway, if the heater (vacuum controlled) flaps (doors) fail to close you are likely to be getting heat in the summertime..

What digger mentioned is a possibility. I always look closely at the bottom seal and the top seal. I run my finger over the bottom seal and the top seal in the filler neck. Your finger can pick up imperfections your eyes might miss. The cap seals in two paces, the bottom which builds the pressure and the top which seals the neck and directs the flow through the filler neck nipple to the recovery tank.

That top radiator hose tells me you may have a clogged radiator or maybe the system is building too much pressure. Too much pressure may prevent the trapped air from purging. Though from your description of the coolant recovery bottle level fluctuating higher on a hot motor and lower on a cold motor, this seems unlikely. If you have an air blockage in the system, it restricts flow and also insulates the heat exchange, both can cause the coolant to boil in one particular area, which makes steam, which adds to the blockage and it turns into runaway cycle.

I mentioned before, a pinhole leak up high where there is often air anyway, maybe hard to spot. Every time the motor goes through a cool down cycle it may pull some more air into the system, air is 800 times thinner than coolant. Had it happen to me three times, that I know of.

I've visually inspected the inside of the radiator end tank, maybe three inches from the outlet and the inlet with a dental mirror and a good flashlight. Wouldn't it be beatch if a clot of casting sand came loose and is plugging part of your radiator, had it happen on my 79 FSJ. Or a piece of plastic got into a hose and you installed it, had it happen on an industrial heat exchanger. Grasping at straws, but when it isn't the likely culprits, it is often something really strange.

As many times as you have emptied and refilled your coolant system, you've likely used enough coolant to float your XJ by now. I always empty at the bottom radiator hose into a big catch pan and inspect what comes out. If you hose down the area under the airbox you can get fairly clean coolant in your catch pan and maybe use it again after you filter it.

GrimmJeeper said:

put a hose with good water pressure in the bottom outlet and pull the top hose, flush it backwards with as much pressure as you can

Click to expand...

So, my plan for today, since I have everything exposed, is to do a straight water flush and backflush, concentrating on the radiator. I have real good water pressure, maybe too good!!. Then start looking for pinholes. Failing any concrete results after ALLLL of this...replace the HG.

Probably what it's been all along. :gonnablow

Not to sound rude, but with all the time you have into this, wouldn't you have save time and money by taking it to a radiator shop? I have found out that it is cheaper in the long run to have a good shop take care of my cooling system.I live in the low desert an our temps run over 105 every day during the summer.I have a all stock closed system in my jeep and run my AC while offroading in the summer, in canyons with no air flow at all.Mine hasn't over heated yet, but i do have them service my junk every 4 or 5 years.Peace of mind for under 100 bucks.
Some thing to think about

scottmcneal said:

Peace of mind for under 100 bucks.

Click to expand...

I'm not worried about being offended...I have nothing to prove and will take any suggestions I can get. However would a radiator shop just tell me "100 bucks, we'll test everything and nail down your problem, and fix it?"

...or would they more likely charge me $90 an hour to do a compression test, exhaust gas test, system pressure test, gallons of coolant, thermostat, cap, etc.?? Only to tell me I had a blown head gasket...maybe. Diagnostic time is billed at $90 an hour (or more) too.

ANY shop around here charges for time, not just to service the system...once. For them to remove the radiator, rod it out reinstall the radiator MIGHT only cost me $100 and if that were the case I'd be there in a heartbeat.

I'm trying to figure out WHY it's overheating, and HOW it has air continually being introduced in to the system, (especially with no exhaust gases in the system) and WHAT if anything I can do about it without spending a buttload money I don't have. Everything SEEMS fine, all the diagnostic testing has ruled out all the usual suspects.

I can replace a radiator and service the system, but I believe have a bigger problem. Thanks.

When performing a combustion leak test load the engine pretty hard and not just having it sit idle.
1. With engine cool remove radiator cap.
2. Start engine and let it get to normal operating temps.
3. Ensure that you have about an inch of coolant below the radiator cap. ( this is so you don't suck coolant into the combustion leak tester and get a false reading).
4. Chock wheels.
5. Place transmission in drive and while depressing brake pedal apply the gas pedal and load the engine for a few minutes.( if not comfortable doing this take to reputable shop) warning don't let anybody stand in the front of the jeep during this step.
6. Place trans back in park and test for combustion leak.
6.

Actually a really good tip, since the heavy bubbling and "boiling" usually starts under a good load. I did just test it at idle. Maybe even take it for a ride around the block.

Thanks

Have you tested the mechanical fan clutch? have a partner start the car while you hold the mechanical fan still with a piece of cardboard. (Keeping hands/fingers clear!).

See if eventually the clutch engages and rips the cardboard out if the way.