Engine Overheat and.... Next Steps (1 Viewer)

[Hidec]

I've just bought a new winter project, and am debating how far to go on the first pass....

It is a 97 LX450 with 237k on the chassis. The PO only owned the truck for a year or so, and before him it lived it's life in AZ. The PO-1 kept every receipt from the early 2000s, and it shows the engine was replaced @216k (rebuilt long block + bunch-o-parts).

The PO said the truck started to overheat and boiled over in December '22, so he took it to a shop that replaced all the coolant hoses and put in a new OEM radiator. He went out and about and it boiled over again, this time bursting out of the radiator and spraying the inside of the engine compartment. He had it towed to the same shop and they said it probably needed a new engine.... The battery was also now toast so it wouldn't start, so he decided to stop throwing $$ at it and sell. Now it's my turn!

Diagnosis so far:

• Coolant leaking out of the radiator bottom when just sitting in the garage. Radiator plastic top tank looks like it bent the aluminum tabs in the center front and rear up / away, and is definitely a leak point now. How it managed to do that I have no idea, but I suspect it is un-salvageable. Planning to remove and take it to a local radiator shop to gather their opinion on repair, other wise will replace.
• The engine starts almost immediately and purrs nicely (with a loaner battery). I haven't run it more than a minute as I'm sure the engine is devoid of coolant at this point
• There are no visible coolant leaks on the engine or from any of the new hoses
• Compression check was as follows:
  • cyl 1 - 150 psi
  • cyl 2 - 140 psi
  • cyl 3 - 130 psi
  • cyl 4 - 135 psi
  • cyl 5 - 125 psi
  • cyl 6 - 145 psi
• Per the SM the engine should be at operating temp, but these numbers were with a cold engine. Cylinders 3 - 5 are lower, however basically at spec, and only 5 to 6 violated the SM 14 psi delta spec.

If you've stuck with this up to here, thank you! My thoughts on possible next steps:

• Fix / replace the radiator so I can bring it to operating temp and see if it holds steady. I suspect it will not, but it might help identify the root cause.
• The min compression numbers on cylinders 3-5 make me suspect there could be a head gasket leak. I would think a rebuilt engine with only 11k would have better compression. A cylinder to coolant channel leak could explain why it continued to overheat on the PO, however this is a bigger job I don't want to just jump into without more confidence it is the cause.
• Perform the "oil down the cylinder" compression check to see if the numbers change (piston rings) or not (gasket or valve). My concern with this is the current numbers could be just fine for a cold engine.

As MUD members have vast knowledge on all that is an 80 series, this is a request for additional thoughts or testing / troubleshooting advice from those that have been there and back already!
Thank you in advance!

 

[ppc]

In my opinion those compression numbers with 20k miles indicate that the long block was not rebuilt. Might have had used engine installed with a "bunch-o-parts" replaced, head serviced but the block was not touched.

 

[robnicko]

I agree with PPC's comments above, sounds like a quick freshen up

Your call however id replace the radiator, thermostat, check the water pump and fan clutch for proper operation & then try it up to operating temp to see how it goes.
Then run your comp tests etc and check valve clearances (cold) as well

you never mentioned but when it is running is there any smoke out the exhaust? if so does it smell like coolant (sweet) or blue ?
is there any milkshake when the oil dip stick removed?

 

[Hidec]

@ppc - agreed on the longblock, even though the receipt shows they charged him for a rebuilt unit.

@robnicko - The engine wasn't running for that long, but the exhaust was free of any odd colors or odors. The oil was changed 1k ago, and still appears relatively golden and un-milkshakey.

 

[Travis 76]

You can also do a coolant system pressure test to see if there any internal leaks without starting and running.

 

[jpoole]

The cooling system pressure test idea from @Travis 76 seems like a relatively easy and low-cost way to learn more.

I'd probably borescope each cylinder as an early step. You could easily combine the borescope checks that with a round of compression testing with oil in the cylinders and potentially learn more about the compression numbers. You can pickup decent borescopes that connect to your phone or computer for cheap online and I'd look for one that has variable/dimmable lighting and good reviews, etc. When looking in the cylinders the main thing I'd be looking for is the sign of steam cleaning from coolant leaking into a cylinder. I'd do this before filling it with coolant and running it very much to try to minimize the risk of potentially hydrolocking it should coolant be getting into a cylinder.

Based on how those tests go and if you don't know what's going on yet I'd probably stick a radiator in it, fill it and run it more, etc.

 

[robnicko]

you can build a pressure tester quite easily.
cut a schader valve off an old bike tube, unplug overflow hose from the overflow bottle cap and insert the schrader valve into it. Secure with a clamp over it and also where the hose connects to the radiator. use a bike pump with gauge (preferably a MTB shock pump with gauge) and slowly pump up till you reach about 15psi. It should hold pressure if all good, if pressure drops look for external leaks however if internal

 

[inkpot]

Sounds like a blocked thermostat is my first guess. Do the coolant leakdown test first. If it holds, then replace thermostat and radiator so you can do running tests. Run engine with no cap on radiator. Should get some bubbles at first to burp coolant system. When upper radiator hose is too hot to hold. Then the thermostat should open and you can see flow in top tank.

 

[Hidec]

The coolant system pressure test is a great idea @Travis 76 . I also have a borescope. Currently the radiator will hold 0 psi pressure, so I can't pressure test in the current state. Based on the excellent feedback, my current plan is now:

1. Take the radiator to the local shop and see if they are willing to try and fix it
2. Either use the fixed radiator or replacement radiator and reconnect to the engine. Even if the radiator is "fixed" I may replace it later in the project to minimize future worry...
3. Without refilling the antifreeze, use air to pressurize the system. I like @robnicko's idea of using the overflow outlet, as any excess pressure should pop the radiator cap v/s some other seal.
4. Use the borescope to check the cylinders while pressurized. I might also be able to hear a leak in one of the cylinders via the spark plug hole.

If I have a confirmed leak into the cylinder, I will pull the head and check valves and cylinder walls and other checkable bits (ex: mating surface flatness), and hopefully find the root cause. The fix and rebuild!

If I have not confirmed a leak, I'll replace the thermostat w/ OEM @ correct clocking), fill the system, and run the engine to continue the investigation (+ an @ operating temp compression check).

Thanks again to this awesome community of folks willing to share knowledge and experience!

I'll keep this post alive with updates as the project progresses!

 

[60 toy ota]

One thought-
Though you can pressurize the system with air, that's gonna be a lot more pumping and you may not see a leak into the combustion chamber like you would a liquid. If cost of coolant is your concern, you can fill the system with distilled water for like $6. Then once you've done your checks you can drain it and move on

 

[Hidec]

Progress Update....

I took the radiator to a local radiator shop, and had a good conversation with the owner (said he's been "in the business" about 30 years...). He said they used to fix plastic tank radiators, but now the labor cost doesn't equate to a price most people will pay v/s new aftermarket. Also said that this one failed like most plastics one do when overheated - the tabs holding the tank to the core bend and the seal breaks. He also recommended to go OEM on this one v/s aftermarket all aluminum. So, I bought a new Toyota rad.

Installed the radiator, filled and bled the system, and hooked up the pressure tester (free tool loan from NAPA). It would not hold 13 psi for more than ~30 seconds. So, out comes the borescope! It was pretty evident cylinders 5 & 6 were leaking just a tiny bit.....

Top of piston in cylinder 6

Coolant drip from gasket at top of cylinder 6

 

[Hidec]

So next was head removal. Once apart, it was evident cylinder 6 was the most impacted, as the piston top was almost shiny! The head gasket on cyls 5 & 6 did not look good

For the head and block gasket residue cleaning I used the WD-40 + scotch-brite pad method I have seen in other posts, and after soaking for a day the old gasket material came off with little resistance.

Next was the big test, and out comes the straight edge and feeler gauges. First up, the block. Spec was 0.05 mm or less per the SM. I could not fit the 0.05mm gauge under any part of the straight edge. EXCELLENT!!! one down and good!

Look at that flatness!!!

 

[Hidec]

On to the head. Spec is 0.15 mm or less. This time it was not celebrations. The 0.178 mm went freely under the bridge between cyls 3 & 4 and 4 & 5, with the 0.203 mm scraping, but going under also.

So, it appears the PO's excursion into high heat land did no favors for the head. Also, the surface under some of the cylinder seals on the head side show this odd patterned pitting:

I'm assuming it has something to do with the mating gasket, but also that the sealing surface is not supposed to have those!

 

[Kernal]

Good work.

 

[Hidec]

So now is the next step planning. I've ready many a post about folks shaving the head and using a thicker gasket, but that it requires decking the block also. I would prefer not to remove the engine for this, especially since the block is still under max spec. So then it means a new or new to me head.

My next step is reaching out to the extremely excellent local LC shops I've worked with in the past to see if they have additional suggestions or rebuild / replace options. I'm also reaching out to Kiwi Cylinder Heads to check non-OEM options. Worst case, it's a new OEM head + other needed parts. Any other suggestions are always appreciated!

Again, I'll keep the updates coming as I adventure onward!

 

[Travis 76]

My head had a .020 warp on the middle. The shop I took it to sourced a used one and refurbished it for me. Runs great and doesn’t burn oil any more.

 

[use2bn83]

Man, none of that screams freshly rebuilt. Those warpage numbers are not bad at all. If there is anything that is not clean on the head on one end of the other, it could be causing a false reading. I’d clean and clean and clean and recheck. What kind of strait edge are you using? What’s it’s stated accuracy? We’re literally splitting hairs haha. I’ve put a 1fz back together that was at .006” of warpage and it’s doing great 18k later. Of course my flat edge was only certified to .0008”/12”

Theres no hard fast rule that you have to deck your block if you deck your head. Check it in the same fashion as your head. Generally speaking both the block on my rebuilds were under .002” of warpage. One had 207k on it the other was 506k+\-

Decking an OHC head kinda gives me the chills. The stress when it gets bolted back down has to go somewhere…. I just picture it going into the cam bores.

 

[Hidec]

Agreed on the recently rebuilt.
The straight edge I’m using claims < 0.003” (0.076 mm) over the 38” length. Worst case it could be contributing and the head is just at or under spec.

My bigger concern now is the patterned pitting where the main cylinder seals are. I assume this is a negative as some of the pits are deeper than the total allowable flatness spec.

If anyone else has experience rebuilding these and knows if such pitting is normal / acceptable, please chime in.

If I believe the receipts from the n-1 PO, this is a 15k old head gasket that ended up failing much too early. Possibly they didn’t torque the head bolts following the SM procedure, the head warpage or pits are bad enough to cause the damage, or something else I haven’t realized yet. I feel like I still don’t have a solid root cause.

 

[use2bn83]

Yea, tough to say on the pitting. Both 1fz’s I’ve rebuilt/resealed had some, not sure it was as bad as yours. Here’s a photo of one of mine. You can definitely see fire ring groove and some pitting, but probably not as bad. The other one was definitely worse.

 

[rebelcruiser]

I read somewhere that I needed to make sure both block and head were grounded because arcing between head , block and fire ring would show as pitting in the softer head alloy. Or perhaps dissimilar metals corrosion?