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Grand Cherokee coolant #2781254
06/03/20 10:59 PM
06/03/20 10:59 PM
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Over the winter I picked up a reasonably clean Grand that wouldn't run. Seller said he was just driving down the street and it died. Sure, whatever, got it for a great deal.

After getting it home and checking the oil and finding 5 quarts of antifreeze sitting under the 5 quarts of oil (no it wasn't all whipped into milkshake) figured they fragged the engine. Pulled the plugs to do a compression check and found one plug sheared off and piston jammed into the head. Bingo!

Picked up a running used motor from a local salvage yard a few weeks ago. Got it in, fired it up started checking things. Everything looked good. Until the temp started creeping up. The overflow started bubbling, temp was still climbing, so I shut it down.

Next day drained the coolant out. The new coolant came out a muddy greyish-brown. Emptied it all out, disconnected the hoses, pulled out the garden hose, put the pressure trigger on it and started flushing the radiator. Started seeing a lot of metallic flakes coming out. Eventually a big blob of mud looking stuff plopped out. Kept the water flowing until it was clean. Looked out the blob of mud and it was shimmering metallic. I'm guessing the previous owner was trying to seal up a perceived head gasket leak or something.

So pushed a lot of water through the radiator. Hooked everything back up, reloaded the radiator with coolant, restarted and began watching. Everything proceeded normal, temp was climbing to normal range, around 210 the electric fan kicked on, temp slowly came down, fan turned off. This cycle repeated several times. Temp seemed stabilized and wasn't climbing over around 220, but after some time, bubbles in the overflow began again, so I shut t down. Figured I'd pick up some radiator cleaner and try another flush.

All that work was on Sunday. Tonight, Wednesday, I decided to drain the radiator. When I began to turn the cap, it was under pressure. A lot of pressure. Like 18# worth of pressure and it started blowing antifreeze out from under the cap..and it was cold antifreeze. So I turned the petcock to drain things. It only took a few turns to get flow started. Had to modulate how far I turned the petcock to keep a steady flow instead of a shooting stream.

So now I'm wondering of a cycle of cleaner and water will work at all. I have never encountered a cooling system that held that much pressure over several days . But it also has me wondering if I might have a cap issue or a bigger problem inside the radiator.

Thoughts?

Re: Grand Cherokee coolant [Re: TC@HP2] #2781390
06/04/20 01:39 PM
06/04/20 01:39 PM
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Alberta
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Sounds like a radiator cap problem. It should only get the pressure specified on the cap. When it cools down, that pressure should diminish. Seems like it built up a lot of pressure, and when it cooled still had pressure residing in the system. Sounds like the cooling system needs a good cleaning and would do that first. The bubbles are concerning. After cleaning and refilling, I would run it with no cap and see if you can see bubbles coming up. Perhaps your new engine has a bad head gasket as well?

Re: Grand Cherokee coolant [Re: 440_Offroader] #2781616
06/05/20 09:20 AM
06/05/20 09:20 AM
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I think a further cleaning is definitely in order. Is there any value in bringing it up to temp without a cap in place? I do have another cap in the garage parts stash I can try out.

Unfortunately this radiator's filler neck is a tube extension off the tank so its impossible to watch the coolant flow by. The possibility the engine has a bad head gasket did occur to me. I might borrow a friends leakdown gauge to test that theory.

Re: Grand Cherokee coolant [Re: TC@HP2] #2781922
06/05/20 09:58 PM
06/05/20 09:58 PM
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One thing about a cooling system holding pressure 3 days after it was shut off would be a pretty good indicator there are no other leaks in the cooling system, or the pressure would have bled off.
I'd change the cap and watch it for a while, I suspect its going to be OK. Gene

Re: Grand Cherokee coolant [Re: poorboy] #2781937
06/05/20 10:29 PM
06/05/20 10:29 PM
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Grand Prairie,Texas
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I think to be on the safe side you should pull the thermostat and flush the whole system again including the heater core. You don't know what junk my have come loose after running it.

Re: Grand Cherokee coolant [Re: stumpy] #2782667
06/08/20 10:42 AM
06/08/20 10:42 AM
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Sunday drained out the coolant, put a jug of cleaner-deruster and filled with water. Ran for 20 minutes using the old radiator cap. The spare cap I have is a 25# racing cap so I figured I didn't want to put that on there. Pressure in the hoses was obviously higher than it probably should be. Cooling system never got over 200* Auxiliary fan never came on. Did observe some occasional bubbling in the overflow but attribute that to the cap issue. Surface temp on thermostat housing was 195*, radiator hoses were 165*, heater hoses were 135*. Heater output didn't seen to be as high as it should be given the coolant temp. Can't really check that with an infared thermometer though.

Next steps are to drain system and see what color comes out of it. New thermostat and cap will be added. While I'm at it, disconnecting the heater core and running some pressurized fresh water through is also on the agenda. I'd like to see if any more stop-leak blows out of it. Based on the heater output, I fear it may have a build up in it.

Re: Grand Cherokee coolant [Re: TC@HP2] #2793542
07/06/20 05:33 PM
07/06/20 05:33 PM
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Update;

Did all teh work outlined above. Filled, ran, and then drained the system about six times before it stopped coming out rust colored with sparkles in it. Replaced the thermostat, replaced radiator cap, refilled system with 50/50 and idled up to 200*. Aux fan came on, everything remained around 200. There was still a fair amount of pressure in the system, temps were consistent with previous checks. After shutting off, still got bubbles in the overflow. I've been limiting use to short trips within a few blocks of home. Everything above has been repeating. Took it to work today, which is a bit further than the few blocks, and temp climbed up to about 220. Turned on defroster to keep it in check, which allowed me to complete the drive.

So it seems I haven't actually fixed anything. It still gets overly hot on occasion and still blows bubbles back into the overflow after shut down. What's next?

Re: Grand Cherokee coolant [Re: TC@HP2] #2793545
07/06/20 05:37 PM
07/06/20 05:37 PM
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220* is not hot on todays engines. They normally, in less that 100*, weather run at 210*.

Re: Grand Cherokee coolant [Re: TC@HP2] #2793651
07/06/20 08:31 PM
07/06/20 08:31 PM
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Buy the kit to check for exhaust gasses in the coolant. Seems the previous owner of the junkyard motor tried to solve the problem of a breached head gasket which allowed exhaust gasses to pressurize the cooling system, with multiple cans or packages of stop leak. This is a classic cause of bubbles in the overflow tank. I hope there's a warranty on the junkyard motor.

Re: Grand Cherokee coolant [Re: 70Duster] #2793878
07/07/20 12:22 PM
07/07/20 12:22 PM
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On the drive home I got stuck in a busy intersection that took several lights to get through. It got up to 240 before i cranked up heater to help draw down heat then I pulled over and let it cool before I finished the drive.

Checking exhaust gas in the coolant sounds like a good next step. There is a warranty on the replacement engine, but it has some time restrictions on it that I'll have to review. Basic compression check on all cylinders looked good, but I did not do a leak-down test.

Re: Grand Cherokee coolant [Re: TC@HP2] #2795187
07/10/20 02:54 PM
07/10/20 02:54 PM
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Got the rig over to an acquaintance that runs a repair shop. He had the tester to see if we have exhaust gas in the coolant...yup, sure did. He also pointed out that I have a 0331 casting head. These have had some problems with cracking over the years. Not consistently, but somewhat frequently enough that the Jeep community will check for them and then decide if other tests are necessary.

looks like I'll be calling the yard to discuss options with them. I can probably get away with a head swap, but I'll see if they want to exchange the whole engine.

Re: Grand Cherokee coolant [Re: TC@HP2] #2812232
08/23/20 12:39 PM
08/23/20 12:39 PM
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Update:

Called the yard I purchased the engine from and explained the situation to them. They said they would provide a replacement if I'd bring in the head. So I began a careful disassembly of the top end. While removing the head bolts, I noticed four front most head bolts did not require as much effort to remove and the left front one came out with most the threads on it stripped and deformed. Examining the head gasket, I could see what appeared to be coolant stains between #1 cylinder and the front most water jackets. Also noticed it had a Victor-Heinz gasket. Not sure, but I don't think these are OEM. A visual inspection of the had did not reveal any obvious cracks. These typically crack between the 3-4 cylinder valve springs or on the deck.

Took the head into a shop for magna-flux inspection. They called and said good news was they could not find any cracks. Bad news was the head was warped .012. I asked if they could cut it to level it out and they said they could. Just got it back this week. I also chased all the head bolt holes in the block with special attention those front four. They all tapped out smoothly and without what appears to be any issue.

Also pulled an oil sample and sent that in for an analysis. Curious about metal content to see if bearings got cooked as a side effect of this. Unlike most 4.0 cracked issues with the engine consuming coolant, my coolant levels never dropped. I simply had extremely high pressure in the system and bubbles. My hope is the engine was not ingesting coolant and diluting the oil, thus saving the bearings, but the analysis will tell me that.

So I'm in $30 for the inspection and $60 the milling, $60 for a new top end gasket kit with new head bolts and valve guide seals, another $20 for the oil analysis. So not too expensive yet.

Re: Grand Cherokee coolant [Re: TC@HP2] #2819929
09/12/20 10:46 AM
09/12/20 10:46 AM
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Finished the top end replacement two weeks ago. Family has been using the Jeep for short trips around town. Results so far look like the warped head was the issue. No overheating, coolant pressure feels like it is really 18# now and not 60, fans cycle when appropriate, and it even idles smoother now as well. Oil analysis wasn't particularly helpful since the oil wasn't run for long enough to determine break down of additives and accumulation of other compounds. It did come back negative for coolant though and they suggested I send another sample in after accumulating a few thousand miles.

Now if I can figure out the clunking suspension in my other '99, I'll be sitting pretty.







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