Blown head gasket?

[MikeDiehl]

Hi guys.

So, my '96 4-Runner (just short of 250K miles) seems to have a blown head gasket.

It had been using about 2 liters of water every few weeks. I found a heater hose that was leaking, but I don't think it would account for the missing water. Fixed it, anyway.

Once I fixed the hose, I refilled the radiator and started the engine. There were bubbles coming up from the radiator fill hole (?) The bubbles didn't stop once the engine got up to temperature, either, so I don't think it's just air in the system.

So far, seems like a HG. But, the engine runs smoothly. The idle is rock solid at ~700 rpm. No oil in the coolant and no coolant in the oil. I don't see any white smoke from the tailpipe, either.

Could this be anything else but a HG? Can it be driven at all? Or does it need to be parked? How much do you think it would take to HAVE it done? My HOA might have a fit if I tried to do it myself.

Thoughts?

Thanks in advance,

Mike Diehl
'96 w/ 248K

 

[delstele]

Any good auto parts store should have test strips...

 

[Team_Jake]

The heater hoses are plumbed to your radiator, so if you had a leaking hose that would definitely attribute to your radiator draining. After you fixed the heater hose, there was probably air in the line and that is why you saw bubbles in your radiator.

If you had a HG leak you would know. Misfires, white smoke, coolant in oil, oil in coolant, etc. I think you're good.

I drove mine for 11 months with a cracked head (coolant leaking into cylinder) before fixing it. I had to replace the head but nothing else was damaged and it's been running perfectly since. So I wouldn't worry about driving it whatsoever.

 

[brillo_76]

I would say you have a antifreeze seep or leak more then a blown head gasket. As others have stated. It's very obvious with the signs of a cracked head or blown gasket..

I had a seep in my rear heater line. I also had a seep with my water pump.

How old is your radiator? As if it's an auto I would replace the radiator every 10 years unless you bypassed the Transmission cooler.

I would be looking for a small seep as your coolant disappearing cause...

Sent from my SM-A505U using Tapatalk

 

[gamefreakgc]

If the bubbles in the radiator have exhaust gases in it, a combustion gas test kit will work. It changes from blue to orange if it is, stays blue if it isn't.

A blown head gasket doesn't always mean there's a mix of oil and coolant. It can happen where the gasket fails between a coolant passage and the cylinder itself and since the cylinder is at a higher pressure (190PSI vs 10 PSI) the compressed air and fuel is forced into the coolant. It then can drain back out or burn off in the cylinder itself.

Keep looking for leaks though. Our rubber hoses are getting really old and brittle.

 

[MikeDiehl]

Well, this is all very good news!

I told my wife that we couldn't drive it at all, so she's relieved as well!

I'll keep looking for slow coolant leaks. I understand that they make a dye that you can add that will make the leaks visible with UV light; does anyone have any experience with that?

I replaced the radiator a few years ago, so I don't think it's due, yet.

I also tried to replace as many hoses as I could when I did my knock sensor in 2018:

Knock Sensor Repairs - What did you do?

I will go and get some test strips, just to be sure. In the mean time, I'll just drive it and see if we can drive the air out of the cooling system.

Thanks for all the good comments. Sounds like we'll have this truck a few more years!

Mike Diehl
'96 w/ 248K

 

[mtbtim]

If you're still losing coolant, get a cooling system pressure tester and pressure test the system.

 

[MikeDiehl]

I was thinking about this some more and I still don't feel that I have an explanation for the fact that the radiator cap seemed to have quite a bit of pressure behind it...

Any thoughts?

Mike.

 

[Bad Luck]

I was thinking about this some more and I still don't feel that I have an explanation for the fact that the radiator cap seemed to have quite a bit of pressure behind it...

Any thoughts?

Mike.

These engines are hard to bleed the cooling system. I highly recommend using this: Amazon.com: Lisle 24680 Spill-Free Funnel, Standard Adapters : Everything Else and elevating the front eng of the vehicle by either using a floor jack or parking on an incline. Make sure to have the front and rear heat set to hot and allow the engine to come to operating temp and give it a couple revs.

In the off chance that you are referring to your radiator hoses being firm after driving that is normal for all vehicles. When you heat a gas or liquid it expands. Your radiator cap is calibrated to keep a certain amount of pressure from that expansion in the cooling system.

 

[Romeo1]

These engines are hard to bleed the cooling system. I highly recommend using this: Amazon.com: Lisle 24680 Spill-Free Funnel, Standard Adapters : Everything Else and elevating the front eng of the vehicle by either using a floor jack or parking on an incline. Make sure to have the front and rear heat set to hot and allow the engine to come to operating temp and give it a couple revs.

In the off chance that you are referring to your radiator hoses being firm after driving that is normal for all vehicles. When you heat a gas or liquid it expands. Your radiator cap is calibrated to keep a certain amount of pressure from that expansion in the cooling system.

I just recently did the parts cannon and replaced all kinds of fun stuff on the 5vz.

One interesting observation I noticed this round is that using with an OEM water pump m, cap and a Toyota thermostat with the jiggle valve the way they want resulted in a super easy bleed out/fill.

I’ve had the coolant out 3 times so far in the last 2 years and this is the first experience with the Toyota thermostat and all new OEM bits on the front. It bled out almost all the way the first time, on level ground, no special funnel, no incline in the garage. Maybe the new heater valve has something to do with it? I dunno. It only took like a quart after the first run and cool down which was odd also. Topped off the de-gas bottle and pulse purged the degas line. I Checked it again yesterday on the incline driveway, and it was full as could be. Again, odd for sure and I don’t have a good explanation why, but the refill was unusually easy for a what a 5vz 4runner typically is for what it’s worth. Not the typical add several times for sure.

 

[MikeDiehl]

Well, this exercise has made it painfully clear that I need to flush the entire cooling system.

Flushing the main system seems easy enough. But I've got a question about flushing the heater core.

I've seen 2 methods for backflushing the heater core.

1. Attach a garden hose, via a fitting and poly tubing, to the output of the core and another tube to the input of the core. This essentially reverses the flow and drains out the input.

2. They make a T adapter that plugs into a garden hose, but requires that the output hose from the heater core be cut, and the T inserted into it. However, something about that host screams "don't cut me."

I really want this system flushed out as well as possible, so any comments or suggestions would be welcome.

Mike D
'96 4-Runner 249K mi.

 

[Team_Jake]

Well, this exercise has made it painfully clear that I need to flush the entire cooling system.

Flushing the main system seems easy enough. But I've got a question about flushing the heater core.

I've seen 2 methods for backflushing the heater core.

1. Attach a garden hose, via a fitting and poly tubing, to the output of the core and another tube to the input of the core. This essentially reverses the flow and drains out the input.

2. They make a T adapter that plugs into a garden hose, but requires that the output hose from the heater core be cut, and the T inserted into it. However, something about that host screams "don't cut me."

I really want this system flushed out as well as possible, so any comments or suggestions would be welcome.

Mike D
'96 4-Runner 249K mi.

You're over thinking it. Get a coolant funnel kit (something like this: link). Drain your radiator, fill it with distilled water using the coolant funnel kit, turn on your 4Runner (with the coolant funnel kit still attached), turn you're heater on full, let your engine get up to operating temp (doesn't hurt to give it a few revs once at operating temp), turn off your 4runner, repeat. Then fill with 50/50 using the coolant funnel kit, keep the engine running until no more bubbles come up out of the funnel, remove the funnel using the no-spill insert, put the cap back on the radiator. Simple and easy.

 

[gamefreakgc]

Unfortunately one cannot just put a garden hose in and just blast out all the coolant. Unless you've got 190 degree water coming out of that garden hose the thermostat will close and not allow any water to make its way through without also removing it. I would recommend the product listed in the above comment or just do it the longer, old fashioned way of fill it up & drain it out once the engine is hot and the thermostat is open.

 

[Bad Luck]

Well, this exercise has made it painfully clear that I need to flush the entire cooling system.

Flushing the main system seems easy enough. But I've got a question about flushing the heater core.

I've seen 2 methods for backflushing the heater core.

1. Attach a garden hose, via a fitting and poly tubing, to the output of the core and another tube to the input of the core. This essentially reverses the flow and drains out the input.

2. They make a T adapter that plugs into a garden hose, but requires that the output hose from the heater core be cut, and the T inserted into it. However, something about that host screams "don't cut me."

I really want this system flushed out as well as possible, so any comments or suggestions would be welcome.

Mike D
'96 4-Runner 249K mi.

I wouldn't want to cut the heater core hose for option #2. If you decide to option #1 use very low pressure and alternate water flow directions.

EDIT: I'd still recommend doing a drain and fill of the entire cooling system with distilled water after you flush the heater core. I also stay away from heater core cleaning solutions but that's just me.

 

[MikeDiehl]

The saga continues...

I wouldn't want to cut the heater core hose for option #2. If you decide to option #1 use very low pressure and alternate water flow directions.

EDIT: I'd still recommend doing a drain and fill of the entire cooling system with distilled water after you flush the heater core. I also stay away from heater core cleaning solutions but that's just me.

So, I figured that since the truck had almost 250K on it, (including a time when I just couldn't afford to maintain it properly) and that the overflow tube was clogged with mud, I'd go with the full flush. I didn't see/comprehend your admonition against using a cleaning solution...

So, I flushed the system and added a cleaner. I have to admit it was nice to finally be able to flush it out nice and clean.

...Now it leaks like a pig.

Looks like it's leaking around the water pump. It's hard to tell if it's the water pump or that probe right below it. But, I lose about a liter of coolant a DAY.

I've been told not to use a stop-leak product in a cooling system. (true?)

So, do I replace the water pump or just re-install it. Either way, I'll change the thermostat.

What are the odds that that probe is leaking?

Any advise is welcome.... and I promise to listen this time...

Mike
'96 4-Runner
250K

 

[Sparky 97Runner]

I've been told not to use a stop-leak product in a cooling system. (true?)

Yes, true. DO NOT use stop leak.

 

[melt757]

I agree do not use stop leak.

 

[melt757]

I was able to flush the heater core by unhooking the hoses of the heater core at the firewall on the passenger side in engine compartment. My 97 V-6 manual cable control is in the center of firewall. I used several different pieces of scrap hose to transition from my garden hose. I was very careful with amount of water pressure used. I also used my air compressor to blow out the hose water.