1988 Toyota 4Runner Intermittent Radiator Problem
January 25, 2012 12:46 PM   Subscribe

I need guidance from car-fixin' types before I take my truck to a mechanic, in order to prevent falling into a money pit of unnecessary repairs. I also need to know if this is a critical immediate fix or if I have time to collect a few paychecks before addressing it.

My truck drove like a charm all the way from Colorado to the Oregon coast and back. The radiator fluid level in the overflow well didn't move a millimeter below the full line, and I never once opened the radiator cap itself. When I purchased the truck, it had a slow leak coming out of the radiator itself that would stop and start with no apparent pattern. The truck has recently started burning rapidly through radiator fluid at times; frequently I will pour about a half gallon of 50/50 green antifreeze directly into the radiator after about 1-2 hours of highway driving, just enough to see the fluid line when the radiator cap is removed. The overflow well is sometimes empty after that amount of driving, and other times it's right where I left it. Sometimes I can smell radiator fluid burning when the temp guage looks normal. Recently the temp gauge on the dash started rising rapidly... I pulled over as soon as I could and saw a lot of white smoke coming from the back of the engine (the side closest to the windshield.) The overflow well was completely full and visibly boiling. I let the truck cool down for about 20 minutes and it was fine for the rest of the day. This has happened twice now and doesn't seem to be related to the length or style of driving. The oil level is also fine and I get regular oil changes.

I wonder if I'm doing something wrong here? The Haynes manual mentions only putting radiator fluid into the plastic well, not the radiator itself, but I started doing that too at the recommendation of a friend. He also said that even though the manual states not to fill the overflow well beyond the full line, that I should fill it up as much as I could. The full line is quite low on the bottle, and I wonder why that is. As long as I keep putting radiator fluid in and watching the temp guage closely, can I keep nursing this thing until I have a little extra money to afford a repair? Or am I looking at the death of the engine if I don't take this in soon? If I do take it in, what should I say to point the mechanic in the correct and most economical direction? How much should I be prepared to spend on this fix?

Thank you so much in advance to anyone who can give me some answers in this situation. I am in over my head, and Google isn't helping me as much as I hoped.
posted by dissolvedgirl22 to Travel & Transportation (18 answers total) 4 users marked this as a favorite
You are looking at engine death if you keep letting it overheating like this. Take it in and find out what's going on. It could just be a $20 hose that needs replaced.
posted by fshgrl at 12:55 PM on January 25, 2012

You've checked the oil level... did you notice anything odd about the oil itself? Was it creamy tan/gray instead of clear tan or black? Was there a white film at the top of the dipstick? Have you noticed any smoke from the tailpipe? (That may be hard to see without an assistant watching from behind the car as you accelerate away.)

Basically I'm trying to suss out if you're losing coolant onto the ground (sticky thermostat, etc.) or are leaking it into the engine and burning it. The latter needs to be addressed yesterday. The former can damage an engine by overheating, but depending on the failure mode you may have time if you stay on top of it.

Other notes: Fill the radiator directly (when cold) only if you REALLY run it low. Otherwise, use the reservoir. Don't overfill the reservoir.. there's a lot of room at the top so when the engine gets (normally) hot the excess fluid has somewhere to go. It'll get siphoned back into the radiator when things cool down again.

The usual questions: does the interior heat work like it used to? Have you ever seen the temperature gauge act strangely? How many miles on the car? Last time the thermostat and/or water pump were replaced?
posted by introp at 12:59 PM on January 25, 2012

You have a spectacularly blown head gasket. The "boiling" coolant in the overflow tank is a giveaway, what you're seeing is the exhaust gas coming out through your leaking head gasket and back into your coolant. I have a Subaru, on which this repair is not cheap or easy because of it's particular engine layout but you may get off relatively easily. I would expect a few hundred dollars to have it fixed, but have it fixed now. It only gets worse from here.

Basically, coolant is leaking into the cylinder and being burned off, which is where the white smoke is coming from.
posted by InsanePenguin at 1:02 PM on January 25, 2012 [1 favorite]

You need to get it to a mechanic right away for a diagnosis and then decide what to do. This could easily be a $20 stuck/broken thermostat (especially if the "white smoke" you've described was actually just steam from boiling coolant, and if you are finding no coolant in your oil and no oil in your coolant) but it could just as easily be a cracked head gasket that will ruin/has already ruined the engine.
posted by RogerB at 1:03 PM on January 25, 2012

Boy was I wrong on price, I just looked an estimate, this is an intense job on a RAV4 as well, expect a charge in the high hundreds.
posted by InsanePenguin at 1:06 PM on January 25, 2012

The oil looks black and normal, no white film, and no reports of smoke from the tailpipe by my sister, who followed me home after the first overheating incident. This happened at a time when both the overflow well and the radiator itself had been filled to the brim, so maybe that was why? The heat works great, total mileage unknown as the odometer is broken but I'd guess it's somewhere between 200,000 to 300,000. Temp guage has always been reliable as far as I know. I have no idea about the thermostat or water pump. My question is, how do I know if it's low enough to warrant filling the radiator directly? Just by looking at the overflow well level?
posted by dissolvedgirl22 at 1:07 PM on January 25, 2012

You have a spectacularly blown head gasket. The "boiling" coolant in the overflow tank is a giveaway

You absolutely can not make that determination from the information given. The coolant was boiling because the engine was overheating, there was insufficient liquid volume to maintain pressure and so t was able to boil. It is phenomenally unlikely that exhaust gas of sufficient volume and pressure to move the liquid in the overflow tank would be visible at idle, or even at full throttle.

This could either be an intermittent leak, or still could be a head gasket. It is possible that what started as a leak along with the several over heating incidents now mean it is a head gasket even if it wasn't before. However, it still could be some stupid little leak. It may well be that filling from the overflow tank doesn't bleed into the radiator if the overall coolant level is down below a certain point - ie the system could look full but there still be an air gap in the radiator. This would give the continuing overheating problem while making you think the coolant system was full. It is possible that the system purged that air over time and the level suddenly dropped (which you have witnessed) and repeated topping and air-bleeding cycles has kept it at bay. However on longer trips the engine was running at the lower coolant level and overheated.

Basically, coolant is leaking into the cylinder and being burned off, which is where the white smoke is coming from.

The white smoke was in the engine bay, rather than the exhaust exit, so it wasn't being burnt by the engine internally. Therefore it is likely an engine bay leak onto a hot area of the engine. This points towards a leak, rather than a blown head gasket (given the proviso of too many overheats above).

So, in summary, I think you have (or certainly started with) a minor coolant leak. This is easily diagnosable with a coolant system pressure tester and the test should be cheap. There's no way of knowing if this is minor by now (after the overheats) without that diagnostic though.

If you want to play your luck that this is still minor, this is what I would do:

Fill through the radiator cap until full (as in, FULL), close it off and then top the expansion tank up to minimum. Run the car until warm with the cap off. Observe how the level reacts over about 8-10 minutes of idling. When the level has stabilised, close the expansion tank cap. Top back up to maximum and check every day and/or every 50 miles and keep an eye on the level. If you have coolant loss it should be much more apparent how much is lost over time. Keep it topped up and if the expansion tank is ever empty when the engine is cold, fill the radiator as above first.

Temp guage has always been reliable as far as I know.

It won't be if your water level is low. If there is air, rather than water, by the sensor it will significantly under read. Always check levels more frequently until you get an idea for fluid volume loss.
posted by Brockles at 1:33 PM on January 25, 2012 [2 favorites]

Sounds like a heater hose is giving way. There are other things than can carry coolant at the back of the engine, but I'd look at the heater hoses first. You'll see two that meet the heater core nipples against the firewall.

The overflow bottle is just that, if there is an overpressure past the cap it is designed to hold the burp up. Before overflow bottles it just spit it out directly on the ground. Antifreeze smells sweet to animals, leading to them drinking it and dying. It is also so you can add antifreeze without popping the radiator cap, which is more difficult if the radiator is hot. Although adding is this way puts a delay on when the radiator sips the coolant out of the bottle. There really isn't a way to tell the radiator level by the overflow bottle.
posted by narcoleptic at 1:40 PM on January 25, 2012

Sometimes, when your radiator is having issues, you just need a new radiator cap. I don't know much about this stuff, but apparently the cap is pressurized or something, and sometimes they stop working. So just trying a new radiator cap may fix the problem, and they're not expensive.
posted by MexicanYenta at 1:42 PM on January 25, 2012

Does your 88 4Runner have a 4 cylinder or V6? I know a lot about the 4 cylinder motors in these trucks, but not as much about the V6.

Regardless of the motor, if this were my vehicle, I would have a shop do a coolant system pressure test. This is a simple, non-invasive test that will reveal where you are losing coolant, but it does require some special equipment. Any radiator shop can run this test for you, but it is best/least time consuming to run it on a cold motor, so if you have to drive it to the shop you will need to wait for the motor to cool down a bit. But a pressure test will absolutely reveal if you have an issue with the integrity of the cooling system, and where that breach is.

Based on my own history with Toyota trucks of this vintage, I'd rank probability of likely causes as:

1. head gasket (either motor)
2. if a 4 cylinder, it's possible/likely one of the timing chain guides has broken and the chain has chewed through the coolant passage inside the timing chain cover.

less likely:
3. bad hose
4. bad thermostat
5. bad water pump
posted by mosk at 2:17 PM on January 25, 2012

I have almost the exact same truck! (1987 4-cyl. 22RE) But I just got it this month, so I don't have a ton of experience with them yet. I haven't even driven mine yet....

I like the heater hose idea narcoleptic raised, or possibly the heater core, because it could explain the intermittent nature of your fluid loss. If it only disappears when you're running the heater, that would corroborate this theory.

That said, Brockles always comes up with better ask-me car repair answers than I do, quicker than I can. So the short answer is, follow Brockles' advice closely.
posted by richyoung at 2:25 PM on January 25, 2012

can I keep nursing this thing until I have a little extra money to afford a repair? Or am I looking at the death of the engine if I don't take this in soon?

Nursing it along is playing with fire. Cooling system problems are the most common causes of engine failure. If your car is worth more to you than a couple hundred dollars then stop messing around and get this fixed now.
posted by jon1270 at 2:25 PM on January 25, 2012 [2 favorites]

Based on your answers, it sounds like there's a coolant leak (for unknown reasons) coupled with you maybe overfilling things for a bit. Given the provenance of the engine, it's good to suspect a head gasket, but if the oil isn't opaque/foamy/filmy and you're not blowing white smoke (given the amount of coolant loss you're describing) it's likely just an old-fashioned leak. Smoke from under the hood means you blew coolant onto exhaust parts.

It could be any number of parts, so you either have to track down the leak or start replacing the usual suspects. The fact that you mention that the radiator itself has leaked could be a lead: it could be anything from a feed hose crack to a cracked radiator to a bad radiator cap. Note that something up top could be leaking and just dripping down onto the radiator. It's silly, but I have to ask: do you leave coolant puddles anywhere? (If you park it after a long drive, etc.)

The smart thing to do is take it to a shop and have them do a pressure test on the coolant system. It'll be a half-hour to an hour of labor and will reveal if there's a straight-up leak somewhere. Worst case you have a cracked radiator. Best case you have a cracked hose or loose hose clamp. If that doesn't show anything, you could choose to pay the money to rule out head gasket (pick a shop that also has an exhaust gas sniffer).
posted by introp at 3:12 PM on January 25, 2012

It's a V6, and I definitely leave coolant puddles, but not consistently. Sometimes I'll be parked two days and not lose a drop; sometimes I'll come out after buying groceries and there'll be enough of it on the ground to see the bright green color. The intermittent nature of the problem is what makes me hesitant to take it in because with my luck, I'll have to shell out for an hour or two of labor just to be told nothing's wrong and then the very next day it will start up again. But it sounds like I at least ought to at least get this compression test done and try to rule out a head gasket problem. Here's hoping I can afford to keep Big Red on the road for at least another year...
posted by dissolvedgirl22 at 3:24 PM on January 25, 2012

If you have a coolant leak, you have a problem. This should have been obvious to you. Your problem, however, based on the puddles is unlikely to be severe* and unless you screwed the engine while overheating it**, is almost certainly minor - worst case you need a new radiator.

*Pray to whichever figurine you like that you didn't screw the head gasket when you overheated it...

**You were dumb to either not fix the leak or at least be much more regular with your coolant level checks once you established you had a leak.
posted by Brockles at 3:28 PM on January 25, 2012

You don't want a compression test, you want a cooling system pressure test. They are different and test different things.

OK, so you have the 3VZE V6. At one time there was a factory recall of this motor due to head gasket issues. It may no longer be in effect due to the age of the vehicle, but take a minute and read this page. It has copies of the official Toyota Technical Service Bulletins (TSBs) regarding this issue.
posted by mosk at 3:41 PM on January 25, 2012

And please clean up the coolant, it kills pets and wildlife quite horribly and they will get into it.
posted by fshgrl at 5:05 PM on January 25, 2012 [1 favorite]

FWIW, I have a Buick and it went through a similar cooling issues. Very erratic temperature spikes, needing to add coolant, etc. I nursed it along for a while then took it to my mechanic. He did a pressure test on the cooling system and found that the intake manifold was blown.
It was not a cheap repair. He also let me know that I was really lucky to not have blown the head gasket or done any damage to the engine due to the extremely high temps. He said that when you are having to refill the resevoir or when your heater blows cold air, it is not the time to mess around. You could be putting off a cheap repair and heading toward a really major problem.
posted by itwasyou at 11:51 PM on January 25, 2012

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