jska

Scratching my head here, but maybe I’m overlooking something simple. Sorry in advance for the long post, but I think the details matter here.

91 Pickup DLX w/ 22RE. ~275K miles, but the top end was rebuilt at 230K according to a PO. Southern truck that I purchased in August and moved up to New England. Ran great for me, but started to experience some idle surging issues as we got into late fall/winter temperatures (could be coincidence).

Popped the hood one day and found coolant had sprayed all over the engine compartment from the overflow hose. Popped the oil fill cap, found some white-ish foam on the underside. Oh no, I immediately think head gasket. Drained some of the oil (had just been changed ~100 miles prior to this episode, was clean) and it was clean still. Read that you can also get condensation on the underside of the oil cap in cooler climates when the truck is driven short distances only (mine is), so perhaps not definitive blown head gasket.

Decided to explore if it could be a coolant system blockage or air bubble issue. Pulled the thermostat to bench test it and prepare for a coolant system flush. Thermostat tested OK on the stovetop, but was aftermarket so decided to order an OEM. While I waited for it to come in, I said what the hell, let me burp the coolant system with no thermostat installed and see what happens (truck was on incline). Burped it, then I drove the truck occasionally for two weeks with no thermostat installed and the truck ran fine. No idle issues, but of course it did not come up to temperature due to lack of thermostat and very cold weather. During the same time period, I borrowed a compression tester and block tester from a friend, and ran both tests. Got an even 220 PSI across all cylinders, and the block test (drawing gases from the radiator fill) passed, repeated it 3x. Also, no white smoke out of the exhaust, no loss of coolant, and no additional white substance found underneath the oil cap. Now I’m thinking it’s definitely a coolant system issue.

Parts finally come in. Flushed the coolant system, replaced the thermostat as well as both radiator hoses, vacuum bled the coolant system (it held 25 PSI vacuum fine) and refilled, and then started the truck. Knowing it still needed a bit additional coolant, I started it with a leak proof funnel attached to the radiator fill.

As soon as the truck started to come to temp, and I presume at the point when the thermostat opened, coolant comes pouring out of the top of the radiator and almost overflows the leak proof funnel. I’m guessing a full quart came out. Shut the truck off, and most of that coolant flowed back into the radiator within 10 seconds.

So, with the truck running and coming up to temperature, something is causing coolant to be pressurized/pushed out of the top of the radiator. My plan is to borrow the block tester again and recheck for exhaust gases in the radiator, but this time while the truck is warmer. Last time I checked the truck was cool (no thermostat) so I’m wondering if I may have a minor HG leak that only shows at temperature. I also have access to a leak down tester, but at this point have a good compression test result as well as a coolant system holding vacuum.

If it passes the block test again, is there anything else this could be? Someone suggested a clogged radiator, but if that was the case, wouldn’t it also present those issues with the thermostat removed? With the Tstat removed, I can clearly see flow across the top of the radiator. If a clog was causing pressurization, it would happen cold too, right? Are there any other coolant lines/passages/valves that would only come into play when the truck begins to warm up as opposed to when cold?

If you’ve made it this far, thanks for reading, and for any suggestions.

snippits

It's normal for the coolant to come out like that right before the thermostat opens. Once the thermostat fully opens, the coolant level will go back down in the funnel. Just changed radiator, and used a coolant fill funnel, and mine did the exact same thing yours is doing. You have to leave lots of empty space in the coolant fill funnel because if you don't the funnel will run over. Even using a coolant fill funnel, these 22RE engines still need to be run through at least a couple hot/cold pressurized cycles(cap on) to get the coolant level proper in the overflow jug.

As far as coolant spraying all over the engine in the first place. Could have been caused by a sticky thermostat or a bad water pump.

swampedout

Id consider getting a test strip and testing your coolant for oil mixture. Rule the HG out for your peace of mind.

Im concerned with the initial spray as well. If it were my truck that would freak me out. Ive had sticky thermos and bad head gaskets and only had the overflow spray on a bad HG.
was your overflow container maybe too full?
sounds like there was a major build up of pressure for that to happen.

swampedout

also, remember your heater system is linked in with this system too.

Have you pulled the rad and ran water thru it to see if its flowing?

jska

What mechanism causes this to happen? Expansion of the coolant in the block before the thermostat opens, and the only place for it to go is out the top of the radiator? If this is the case, it would mean that it expands and overcomes the direction of the flow of the water pump.

The peculiar thing is as soon as the coolant started filling up the funnel, the idle surging issue began. The truck was revving to 2000 rpm, then erratically stay there/drop down to 800 rpm and go back up again. This is the same behavior I observed prior to the incident where coolant sprayed everywhere under the hood.

Agree, there was a major build up of pressure. No, the overflow wasn’t too full, if anything it was low. Are the test strips more accurate than the block test fluid? I’ll see if my local parts store carries them.

Understood. When this occurred yesterday, heat was on full blast as I was burping the coolant system. I can’t recall if the heat was on when the initial episode occurred. I can try running it today with the heat off to see if that effects the idle surge/coolant overflow.

No, I haven’t pulled the radiator, however when I flushed the coolant system with distilled water, it filled and drained through the petcock multiple times with no issue. Also, with no thermostat installed, I can observe water flowing across the top through the fill hole.

snippits

Idle surged because coolant was low in the IAC. The idle surge should stop once it is full of coolant. First time I changed coolant on my 92 22RE, it did idle surge. This last time I just replaced radiator, and then refilled with just over one gallon of 50/50, and I did not get an idle surge. When I did a coolant change years ago, apparently the IAC got low on coolant, and it was idle surging, and I said WTF is going on now.

For what it's worth. About a year later after the first coolant change, I did have to change the IAC because of random idle surges. Coming to stops(brake pedal depressed) the engine would be idling too high. Then the fuel cut would kick in causing a surging idle. I replaced the IAC, and it has never done it again.

jska

Thank you. I’ll drain a bit of coolant out of the radiator to make some room for expansion, jack up the front of the truck, and let it heat up and be more patient this time. I figured vacuum bleeding/filling the coolant system would have alleviated any of these issues, but I suppose not.

Guess it might make sense to pull and clean the IAC first, just in case the coolant lines are gunked up.

snippits

Are you sure that a bad radiator cap did not cause the problem in the first place?

If it still has original hoses for the IAC, I would definitely replace them. One of the hoses(Gates 18222) is like $40 plus if you buy the Toyota part. Fortunately, you can still get Gates hoses that will work just fine. Gates 18222, Gates 18223, Gates 18400, and you will have it covered. I bought all of the above back in 2017 from Amazon, and they are still doing good.

jska

I’m not sure of it, but I have replaced the radiator cap since the incident with a new OEM cap. The hoses you listed look like the heater core hoses, not the IAC hoses. Should be two small hoses for the IAC, correct? EDIT: Double checked, and I am wrong. Not sure what 18400 is for off the top of my head but will poke around and see if I can find where that one goes.

snippits

Gates 18400 is the bypass hose. Most auto parts houses around here keep that one in stock. It goes from the bypass union under the intake to the pipe on the backside of timing cover passenger side. Might as well replace it while you are doing the two IAC hoses. It's a U-shaped hose, and it should be the cheapest of the bunch. Picture is from 22reperformance.com.

jska

Thank you, and will do.

Quick overall update — had a few minutes this afternoon, and figured I’d start the truck up with the radiator cap on and see what happens. Heat was off in the truck so it would heat up quicker (20F outside). It came to temp on the gauge and then began to overshoot the middle. Felt the upper radiator hose and it was cold. Also interesting to note is that as the truck passed halfway on the temp gauge, the idle began to rise. Shut her down, and took the radiator cap off slowly and there was a ton of pressure built up.

So, with no thermostat in, coolant flows fine (can verify visually), radiator hoses get warm but not hot, but truck does not come to temp (because of how cold it is currently). With a brand new, OEM bench tested thermostat in, coolant doesn’t flow, radiator hoses stay ice cold, but pressure builds in the system. I suppose it could be an air bubble sitting underneath the thermostat preventing flow? I thought the vacuum bleeding would take care of air bubbles, but I’ll try the old fashioned burp again, too.

Didn’t have the time to run to the auto parts store to rent the block tester again, maybe tomorrow if I have time.

laegion

Sometimes with a partial blown head gasket leaking combustion gasses into the coolant (over-pressurizing the coolant system) the cylinder only leaks much at higher compression (high load/RPM/throttle), so you'll only see it happening when you're getting on the accelerator. I don't think that's what you have here but it might be worth consideration.

jska

I appreciate the input. I've thought about this too, but figured if this was the case I would have exhibited issues while running the truck without the thermostat. With it out, I used the truck like normal, multiple runs to the dump hauling 500+ lbs in the bed. However, no overheating, no smoke, no loss of coolant, good compression results with the thermostat out. My only theory that would support this is that the headgasket only begins to leak when the truck approaches operating temperature. However, that seems counterintuitive, as you'd think heat would help the headgasket seal better...

My next step at this point is a full leak down test, just gotta find the time to do it. Hopefully early next week. I'll keep everyone posted.

jska

Update: didn’t have time to leak down test the truck today, but figured it wouldn’t hurt to jack up the front end and manually burp the cooling system again. Burped for about 45 minutes, cycling the heat on and off. Had some idle surging, but all of a sudden it would suck all the coolant in the leak proof funnel back into the radiator and the surge would stop. Maybe that was large air bubbles being trapped, then escaping?

Got it to a point where the coolant level was pretty stable, and put the radiator cap on and took it for a 15 minute drive which included some hills.

Temperature gauge stayed more or less half way, except a few times where it crawled up to ~2/3 (engine braking down a hill), but it never got close to the red. Stopped halfway and it idled good. Got back home and popped the hood. No coolant explosions out of the overflow. There was a slight bubbling in the overflow tank, maybe one bubble every 3-4 seconds. Not sure if this is normal because I’ve never looked this closely before.

Tomorrow I’m going to block test it at operating temperature, drawing air from the leak proof funnel. If it passes, I’m leaning towards this NOT being a head gasket, but maybe a failed thermostat/radiator cap (both since replaced) and a radiator that may need replacing (I don’t think my temperature gauge should be going pass half way). I’m also planning on replacing the remaining coolant hoses that I haven’t gotten to (heater core and IAC/throttle body) as well as cleaning the IAC/throttle body.

Jimkola

The block tester is one of the most reliable tools for testing a headgasket, but sometimes reading the color reaction can be a little tricky. On the 22R# is was pretty consistent that a bad headgasket would cause a fairly quick color change from the deep blue to a shade of yellow. I'd say within a minute if the coolant was flowing in the radiator.
The reason I mention this is if you leave the block tester on long enough you will see the blue change color, even if the headgasket is ok. I've seen people leave them on for 5-10 minutes and it'll go to some shade of green. I don't consider those valid test results.

jska

Today’s update: Block tested it twice with the truck at temperature and the coolant flowing, and it passed both times. I was pumping the bubble for at least two minutes each time. Verified both times as well by pumping it at the exhaust where it changed to yellow within 10 seconds.

I also used an IR thermometer to check radiator temps, and I got about 140F at the top, 110F at the bottom, but the middle fin sections were about 50F.

While it was running, I again had a few episodes of idle surge where it surged to 2000RPM, the leak proof funnel filled with coolant, and then all of a sudden it sucked all the coolant back in and idle went back to normal. I’m thinking I may have IAC coolant flow issues.

I’m going to pull the throttle body and IAC and clean both (need to order new gaskets, first), and will replace all the remaining coolant hoses (IAC and heater core) at the same time. I’m also going to put a new radiator in, and then burb the whole system again.

While I’m not 100% out of the woods yet with respect to the head gasket (it could be a very small, intermittent leak), I’m feeling better that this is a coolant flow / IAC issue.

Stay tuned...

swampedout

Sounds like youre doing good on chasing it down!
keep it up.

My reading comprehension skills are horrific so excuse me if youve already covered this but are you running a 2 stage thermo?

snippits

If your are going to take the IACV apart, you will need a new gasket, and I could not find one around here locally in stock. The screws that hold the IACV to throttle body are a PITA. Mine would not move with a good long handle screw driver. Bought an impact phillips bit, and my impact wrench spun them right off without stripping the heads.

22RE Performance has a seal, hardware, and allen wrench kit if you need it. Standard Motor Products AC141 IACV comes with a gasket. I bought a new set of screws from my local hardware store.

https://22reperformance.com/intake-e...ta-parts-gtb2y

Jimkola

the 22R# wasn’t known for having intermittent headgasket issues. Either it failed big, or started small and got big fast. If it passed the block test, combined with solid compression numbers, I think it’s safe to move on to scrutinizing other components.

jska

No. I replaced the aftermarket one with an OE single stage. I wish I had bought the dual stage, though, as I’m seeing some temperature overshoot with the heat on. I think I’ll just drill out the jiggler valve for now and see if that improves the situation.

The kit is already in my cart, along with a new throttle body gasket and idle screw/o ring. Thank you!

I appreciate the perspective. That’s the current plan — overhaul everything coolant touches, including the radiator.

Which brings me to this question — I see two options for replacement. The CSF 2314 which is popular here, or OE. I found a local dealer that has the OE radiator in stock for about $280. I think it’s two core, vs. the three core of the CSF (which can be had for about $210), but I’ve heard of some quality issues with the CSF. I’m leaning towards OE at this point... Anyone have an opinion?