Head gasket recap (1 Viewer)

[aim]

What started as a #6 cylinder HG leak and ended with a complete engine rebuilt on my '94 (thank you IDoug, CDan, and many, many others) is now done. The only unexpected casualty was the oil pressure sender harness. Below are some oddities that I haven't seen mentioned.

1. I was having zero oil pressure on the gauge. Backing out the sensor did not result in any leakage of oil around the threads. I was advised that a possible cause could be my having filled the oil filter prior to installation ("the mostly empty oil pump cannot build enough pressure to force the oil through the oil-soaked filter media"). Having replaced the oil filter with a dry one and removed the oil pressure sender completely, I proceded to shoot a stream of oil out the passenger side and over the tire, thoroughly coating my whole garage with clean oil. It is not clear wether the harness was the problem (it was VERY corroded) or wether I in fact had no oil pressure. Still, food for thought.

2. The front heater core attaches to the DS copper pipe with an o-ring and a little copper clip. Neither the o-ring nor the clip are available from Toyota (at least from my local dealer on a 2-day's notice). I reused the clip, replaced the o-ring and am hoping not to have to take the whole dash apart yet again.

3. I did the RT temp gage mod. Works great, with one caveat. Whenever I engage or disengage one of the difflocks, the gauge briefly goes to zero (cold), bumps around a couple of times and returns back. My difflocks are retrofit, with a 'custom' rear harness, so that may be a contributing factor. I am pretty certain that the indication is an artifact of the difflock switching and will study the diagram to see if the bulb or the relay could be influencing the temperature gauge. If anyone has seen anything like this and has any ideas, input is very welcome.

4. The pipe from the thermostat housing to the head (the L-shaped one that attaches to a nipple at the back of the water pump) was leaking at the bottom (despite all new o-rings). I had to resort to an oversize o-ring to stop the leak. More cooling system leaks (fortunately found *before* I put coolant in) were due to my having used silicon grease as a lubricant during pipe-to-hose assembly (all those connections at the firewall and the PS side of the head. Much wiping, cleaning and Breeze constant-torque clamping ensued. Be careful!

In conclusion, everyone is right. Buy parts from the 'mud vendors; farm out as little of the work as possible and only after careful negotiation (my block got cut far more than I wanted, the freeze plugs weren't done the way I wanted, etc... despite very careful discussion ahead of time); bag, label and photograph everything; search 'mud for the answers. Thank you, everyone!

By the way, the complete cleaning and overhaul did not cure my very low startup idle issue ( https://forum.ih8mud.com/80-series-tech/101950-low-idle-after-disconnected-battery.html ). I consider myself lucky that the solution remains simple and permanent.

 

[aim]

What started as a #6 cylinder HG leak ...

2. The front heater core attaches to the DS copper pipe with an o-ring and a little copper clip. Neither the o-ring nor the clip are available from Toyota (at least from my local dealer on a 2-day's notice). I reused the clip, replaced the o-ring and am hoping not to have to take the whole dash apart yet again.

...

June 2016 update: the o-ring leaked. My dash is out again and the heater core is back on my bench. The o-ring I used before was a 16mm ID, 20mm OD. The clip seems to hold up, the o-ring clearly does not. Good thing it's motorcycle weather...

 

[l1coeea9]

June 2016 update: the o-ring leaked. My dash is out again and the heater core is back on my bench. The o-ring I used before was a 16mm ID, 20mm OD. The clip seems to hold up, the o-ring clearly does not. Good thing it's motorcycle weather...

Yikes! When I did my heater core I eyeballed an o-ring size and just went for it. Two years later it's still going strong.

 

[baldilocks]

June 2016 update: the o-ring leaked. My dash is out again and the heater core is back on my bench. The o-ring I used before was a 16mm ID, 20mm OD. The clip seems to hold up, the o-ring clearly does not. Good thing it's motorcycle weather...

Would you mind posting a few photos? And maybe document this repair process?

 

[aim]

A post that claims that the clip and o-ring can be bought: 1995 - Heater core and hose/pipe?

All I can say is my radiator shop dude isn't salty enough (he has lake-front property) and doesn't have anything like this.

My progress has been mostly regressive so far: the 2011 o-ring leaked, the used replacement heater core assembly leaked, the 2011 core with new o-ring leaked (but not at the o'ring!), so my dash has now been apart 3 times in the last week.

I am now reassembling the vehicle for what I hope to be the last time.

 

[aim]

Below are a couple of pictures of the heater core assembly once removed. The pictures are of the used core I purchased, so the crusties are yellow. Mine were pink, since I used Toyota Red coolant. The junction leaks at the bottom, runs down the vertical reinforcement and then down the horizontal rib to either side, ending up in the inner upper corner of the driver or passenger footwell, depending on which way the Cruiser is leaning.

Please note that this is not my original core, hence the lack of buildup on the horizontal rib. Mine was covered in pink goop.

What a slight leak looks like:

This was washed somewhat, since I filled my system with water, pressure tested it, and flooded my passenger footwell.

 

[aim]

My thoughts on the o-ring:

I ended up picking an o-ring by eye. If it's too "plump", the flanges of the two pipes don't meet and the clip doesn't squeeze them properly. If the o-ring is too skinny, the two flanges meet, everything looks good, but the o-ring leaks eventually. I ended up picking the fattest o-ring I could find that would still allow the flanges to be squeezed together by hand. Once you release the flanges, the o-ring springs back a bit. In my sleep-deprived and contorted state I now believe this to be the magic combination of factors. If this leaks again, I am brazing this b*tch.

I didn't obsess over ID and OD like I did last time. In particular, I ended up choosing a plump o-ring with a rather small ID. Seemed to work.

Note that in my case, a leak developed after 24 hours. That is, I assembled the core, vacuum-bled the system, pressurized it, saw no leaks and no drop in pressure, put everything together, and was just about to drain the water and put the coolant in when I noticed the wet carpet.

As per @Kernal:
here is a place that sells metric o-rings: Japanese (JIS) O-rings : The O-Ring Store LLC, We make getting O-Rings easy!
here is a compatibility chart: https://www.sealingdevices.com/documents/oring_chemicalcompatibility.pdf
it was suggested that Dow Corning O-ring lubricant #55 be used. Don't know about #55, but I used Dow Corning vacuum grease 5 years ago and was *NOT* happy with the outcome.

Here are some pictures:

Detail of the junction, with the clip, and a (too-thin) o-ring.

Here is the detail of the "inlet pipe" - the little brass pipe on the USDS side that is attached to the heater core with the o-ring:

The pipe is 16.5 mm OD. The o-ring is the one from 2011.

Here is how that junction looks from inside the vehicle. Note that there is very little clearance, and a "safety hose" as proposed here: Heater Core O-Ring Backup Seal is unlikely to fit. It is also impossible to see a leak. This is dead center of the vehicle, under the lip of the windshield, with the steering wheel brace and all ducting removed.

 

[aim]

A final comment on leaks, before we start on the reassembly process.

The heater core has two pipes that go through the firewall. I had a h*ll of a time getting the passenger side outlet nipple not to leak. I replaced the 5 year old Toyota hose with a chunk of Green Stripe and thought I got rid of the leak. Instead, the coolant leaked along the pipe and down along the inside of the firewall. I figured I needed the practice, so I took everything apart again, pulled up the rubber pad on the inside of the firewall. That, and I couldn't believe it wasn't the o-ring... I strongly recommend you NOT push the hose on too far. Much better to see a leak dripping on the exhaust manifold than to towel up coolant from the carpet...

 

[baldilocks]

Excellent info! Thank you.

 

[aim]

Here is my o-ring choice. I am not suggesting it's the correct choice, nor even that my way of choosing the size or material are valid. I am merely putting down here for reference what I chose after ripping the dash apart for the third time.

I went with an HNBR 10.9x1.9mm o-ring from a kit I managed to find locally.

 

[alia176]

Excellent documenting, thanks for the effort.

 

[Kernal]

aim: Did you happen to get a measurement (OD) of the pipe flange (or estimated OD)?

Consider using some type of rubber tape or FIPG over the flange (insurance) before clamping it down?

Any thoughts on eliminating the O-ring and soldering that union, would that work?

 

[aim]

aim: Did you happen to get a measurement (OD) of the pipe flange (or estimated OD)?

23mm:

Consider using some type of rubber tape or FIPG over the flange (insurance) before clamping it down?

I did, but I chickened out. I have a few tubes of stuff, but didn't really trust any. Besides, I was sure I would be back on the road and was rushing to beat the rain. Little did I know...

Any thoughts on eliminating the O-ring and soldering that union, would that work?

Absolutely. With a large soldering iron, a fine tip torch, or a reliable radiator shop, given the right solder, I would have done it already. My guess is that the o-ring business has to do with standardizing the heater core rather than any function. The inlet pipe does not need any play and does not rotate, since it is clamped at multiple points to a rigid piece of plastic. Next time, that is what I'm doing. The solder I had access seemed to me to be too brittle. There is *significant* play between the two pipes, and you would need quite a pool of solder.

That being said, unlike the 60 series, there is plenty of pipe before you get to the brazed connection to the radiator. A wet rag should allow one to heat the joint thoroughly without endangering the integrity of the core.

 

[aim]

Excellent documenting, thanks for the effort.

Probably should be moved to a separate thread, as it no longer has anything to do with my head gasket repair.