Overheating & gurgling behind dash

I have a '96 rwd with about 199k on it. I bought it from the previous and original owner who had the head gasket replaced around 30-40k miles back. I put about 7k on the van and recently after relocating to Texas had the van start to run hot and come close to overheating (never touched red on the guage but climbed significantly) on a drive on a fairly hot day in the texas hill country. I parked the van and there was a strange gurgling sound coming from behind the dash. I let it sit over night and drove home the next day with no issues.

The significant climb on the guage is now a common issue on hot days. A couple days ago I flushed the system. It looks like the previous owner or garage at one point mixed green and orange coolant in the system. I used a prestone flushing agent and follow the flushing directions and drove it with the agent in the system for 1-2 hours. After an initial cycle the system seemed to be working and heat was going fine. I drained this out and flushed once more in the drive way with distilled water and ran with water only in the system for 20min. Finally drained out and replaced with toyota pink/red coolant (premixed - off brand) filling coolant in the reservoir tank to midway between the low and full line. I started the engine with cap off and let the system come up to temp and once at temp ran the heater full blast with the radiator cap on for about 10min. Heat seemed to be working. Since that time I can't drive long without the temp steadily climbing towards the danger zone. After the first 2-3 highway drives I would park and turn the engine off and coolant would rush from the overflow hose that spills out on the passenger side under approx where the battery is located. Now it's not spilling out but the gurgling noise persists, heat only works when foot is on the accelerator and there's a lot of coolant foam that will spill out from the overflow tank if the cap is out.

Obviously there's air in the line. I'm curious what else could be going on. Anyone have any advice or tips to resolve the issue. Thank you!

I can't help you with actually fixing your problem, but a tactic I've used in the past on a vehicle that would overheat to help prolong it's drivability, is a trick I learned about on CarTalk. If the engine's overheating, crank the heat up while you're driving. It's horrible in the summer to be driving around with the windows open and the heat blasting, but it definitely helps keep the engine cooler.

Mine is a 91, so I'm hazy on the different S/C cooling system, but have two questions based on N/A experience:

1. When you flushed it, did you pull the thermostat and the block plug?
2. How much coolant did you need to fill (and is it full now)?

I'll add some detail to John's post, since I remember reading stuff by folks who referred to things and thinking "whaaaat?"

To properly drain everything, there's a block engine drain plug under the engine on the passenger side, near to and recessed up above the hose to the oil pan. Obviously not a gurgling issue, just a drainage detail. You get everything out including fluid pooled at the bottom of the engine block when you remove this.

Also, to make sure the air at the topmost part of the cooling system in the engine block is expelled, it pays to remove a bleed screw above and to the left of the coolant sensor and making sure coolant comes out of it (as you fill - you could obviously remove it to expel any trapped air there if the coolant's already been added). That is located on the metal "backwards-S"-shaped coolant pipe you'll see when you remove the passenger-side engine cover.

(photos courtesy of the late great Yahoo Previa Group archive)

Also here's the opinion of Eric Collins, one of the gurus of the group. FWIW I never did the tilt-the-front-end-up thing.

[Source: Yahoo Previa Group Archives - "Previa Coolant Fill Suggestion"]
That's what I do too -- with the front end lifted, I fill the system with distilled water, run the heater on max, hold the revs around 2500 rpm to warm up the engine and get the t-stat to open, then I can usually put another gallon or so of water into the system. Then I drain the radiator and the block, and repeat this about 6-8 times, or until the drain-off looks clear. After that, I know the system is 100% distilled water, and can then add 50% coolant (based on total capacity of the system) to arrive at a perfect 50/50 mix. I let the coolant circulate through the system while the van's still lifted too. Then just top off with more water to the "max" line of the tank once the engine has fully cooled (usually the next morning). Might have to top it off a few more times until everything settles.

FYI, I love to use something called a spill-free funnel - it has an adapter that tightens into the radiator cap opening, and then a deep funnel press-fits to that, so that while running the engine, bubbles coming out don't make splashes all over and expanding coolant doesn't overflow. When you're done, there's a plug-on-a-stick that you insert in the funnel to block the bottom, then you pull it off and drain it elsewhere. No muss, no fuss as the saying goes.

Thanks for this and I appreciate the images - those are helpful. I did not access either drain plug when I did the flush. I drained the original coolant out using the white drain plug on the passenger side with the van front end on ramps. I flushed the sytem out with distilled water and then filled it with distilled water + the prestone radiator flush fluid (1 bottle ~12oz). I ran the system both driving and just keeping the revs high for about 1 hour drive time total, running the heat the whole time and then let the system cool overnight. The next morning I emptied it and flushed it before flushing again with 2 gallons of distilled water.

After draining another time I filled with about 1.5 gallons of toyota red/pink coolant (premixed - no dilution). That brought the coolant up to the max line in the reservoir. I filled the system through the reservoir. That's when issues occurred. Multiple times the reservoir would boil over through the excess drain pipe and I would see fluid come out from just bside the front passenger wheel.

At this point the issue has really happened in about a week. It hasn't been as hot but we did have a day in the high 80's, full sun yesterday and I drove around for 45min with the ac blasting and in stop/go and highway situations. The temp guage was more active than I'm used to but never went about 3 o'clock or straight in the middle depending on how you think of it. Most of the time it rest in it's normal 3:30 position.

I'm still a bit concerned as I'm going to embark on a longer journey in the next month on a move but the system seems fine and the van is now running well. Perhaps the final bubbles made their way out of the system? I'm inclined to let it be if no problems persist but I'm interested in the bleed screw. The coolant in the reservoir is low and sitting below the 'low' mark but when I last added coolant it gurgled out of the overflow hose as referenced earlier and after that it's been fine since. This system has perplexed me to say the least.

Most likely it's OK. You began this thread by observing that heat was not reliable, so "obviously there's air in the line." So you observed that air in the system will form a pocket in the heater core and impede heat transfer. That likely was the sum of your problems, and now appears, from your observations, to be better.

That air pocket displaces coolant, so as it works its way out the level will drop. It sounds like you saw that and topped up, so all the right things are happening. If the heater now responds quickly to the control valve, the bubble has probably passed. Keep an eye on the coolant, which sounds like it has settled now, and otherwise don't worry about it. At least you know how to make it easier next time.

Quote:

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Originally Posted by John Kaufmann

It sounds like you saw that and topped up, so all the right things are happening. If the heater now responds quickly to the control valve, the bubble has probably passed. Keep an eye on the coolant, which sounds like it has settled now, and otherwise don't worry about it. At least you know how to make it easier next time.

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Thanks John. I'll keep an eye on it. I hope and think you are right and that everything is okay. I have only owned the van since the fall so the slight variation in temperature during hot driving may just be normal :?: Regardless I've put in about 400 miles of highway and stop/go mixed driving and haven't had any issues in 2 weeks.

In terms of topping off coolant, at this point is it likely safe to just pour directly into the reservoir or should I take precautions of putting more coolant in another method to prevent air bubbles? I assume the bubbles are really just possible when the system is empty and being filled. I've read some suggest pouring coolant through the upper radiator hose though. Thanks.

Quote:

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Originally Posted by John Kaufmann

How much coolant did you need to fill (and is it full now)?

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Also to respond to this I was able to put just over 1.5 gallons into the system so less than I expected but that's also about what I drained out originally so I wasn't concerned. I drained while lifted on ramps.

Quote:

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Originally Posted by ccrnnr9

... at this point is it likely safe to just pour directly into the reservoir or should I take precautions of putting more coolant in another method to prevent air bubbles? I assume the bubbles are really just possible when the system is empty and being filled. I've read some suggest pouring coolant through the upper radiator hose though.

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The point of pulling the upper radiator hose is to try to assure that, as you fill, any air in the system is in that open part, and so will just bubble up into the reservoir when you connect it. (After that, you should still get a half gallon into the system.) That is good for when you start to fill the system, but you are past the point where that will help.

Everything had run fine for a couple weeks about 350 miles. I loaded her up to hit the road for a move to New Mexico and while the temp fluctuated in the higher temps and sustained climbs it wasn’t an issue and never got outside of the middle range of the temp gauge on the dash.

After arriving in NM it’s been constantly climbing to levels where I don’t feel comfortable driving it and have to pull over to cool down. I have to nearly always run the heater to keep the temp in check and that’s troublesome for numerous reasons in the summer. Added to that the heat only works intermittently. It seems like there must still be air in the line. I’m curious if anyone has additional tips for getting that air out of the line. It sounds like I may have to wait till I get home to be able to access that bleed valve. Otherwise I may need to take it to a mechanic familiar with Previas here in Albuquerque. I’ve never had great luck with mechanics with these eggs but maybe someone has a recommendation? Thanks for the assistance!

See if there's a place you can park it significantly nose-up to run for a bit so air - if that's the problem - could migrate from the engine block to the front?

Not to be negative but it sounds like my 95 just before the head gasket blew...in New Mexico...

I've heard Scotty Kilmer talk about a chemical kit you can get to test for exhaust gas chemicals in the coolant, maybe that's worth doing. I started to get white smoke before things got bad and garaged the van until I could fix it (vs the Toyota service rep's "just drive it until it dies"). If it's really developing a head gasket problem, better to know sooner than later.

Its also worth noting that I had work on the cooling system 2 months earlier by a place that was pretty clueless, so I may have been driving around with a big bubble for 2 months, if that's possible. I recall being suspicious about that possibility. However I had suspected head gasket trouble even a year earlier, when I put Bar's head gasket fix in it. So either of these may be viable theories