Overheated - Assessment

[AppleTech]

So I'm helping a friend with a 2UZ-equipped vehicle (it's not a 100 but I wanted to ask here since I know I'll get a quick response). It overheated during a drive around town enough to cause pinging/noticeable performance issues and throwing the christmas-tree of warning lights on the dash. He pulled over and had it towed to a shop. After it cooled, shop filled it up and he was able to drive it home but it used up about a gallon of coolant on the short drive home (but did not overheat). They diagnosed it as a leaking HG (no visible coolant leaks). Shop is telling him to just buy a new motor ($9.5k installed) which seems a bit overkill to me.

I went to his place tonight and ran a compression test - ~180 across the board and all within 10 PSI of one another. We also drained the oil - it was apparently changed a couple days before the failure. It does not look like new oil (fairly brown) but the viscosity seems good and it did not look like there was water in it. No metal shavings/sludge visible, so I don't think the internal damage was too great.

He's got a quote to purchase HG, timing belt (while you're in there), water pump, etc. and I offered to help him do the repair. I told him that doing the repair is a gamble with his time and the parts money, but it sounds better to him than 9K. To ease the pain, he has another 2UZ vehicle he can always pull the water pump and timing parts he bought new to use later.

As the truck sits right now, it will start up and idle/rev normally (sounds just like my 100 series of the same year, which is in good health), so I don't think the motor was irreparably damaged.

1. Is my testing approach and reasoning sound?
   
2. Can a machine shop check the heads to see if they warped?
   
3. If they did warp, do you get them resurfaced or do you replace them altogether?
   
4. What other items might need to be checked/replaced as a result of overheating?

I've never had a truck overheat before so just looking for some guidance. Thanks in advance!

 

[re_guderian]

If all of the cylinders tested ~180, which head gasket are you going to change? Have you pressure treated the cooling system/radiator? I'd do that before tearing into anything. And I'm not a huge Blackstone fan , but this is precisely the kind of thing they're good for -oil analysis to check for coolant in the oil -or not.

 

[Julian Stead]

Is there white smoke coming out of the exhaust?, if the head gasket has gone you would either lose it into the cylinders(white smoke), into the oil galleries(creamy sludge), or external leak( visible leak on outside of engine). I would remove all spark plugs and check to see if any have been cleaned up by water(steam) entering the cylinders, check for any visible leaks. I would burp the system and run the engine and see if the system is pressurising, the new oil will be shot due to heat. If the garage that diagnosed the head gasket being that there was no visible leak then take it somewhere else for a second opinion as a gallon of water lose over a short period should be evident even if it is internal. If it is proven to be the head gasket then you have to weigh up the risk of a repair to a replacement engine, I don't think 9k is a reasonable price either, if you can change a head gasket then you can change an engine so you could do the engine swap yourself.

 

[Sandroad]

So how's this for a scenario? Thermostat stuck closed on the drive around town caused overheating and loss of coolant out the expansion tank. When it cooled the thermostat freed up but the shop only filled the expansion tank and radiator without "burping" the engine. When the engine block refilled with coolant on the drive home, the system appeared to lose a gallon, but didn't really. Your testing showed good HGs and there is no external leak. So, change the oil, replace the thermostat and coolant and you're good to go.

 

[camino70]

So how's this for a scenario? Thermostat stuck closed on the drive around town caused overheating and loss of coolant out the expansion tank. When it cooled the thermostat freed up but the shop only filled the expansion tank and radiator without "burping" the engine. When the engine block refilled with coolant on the drive home, the system appeared to lose a gallon, but didn't really. Your testing showed good HGs and there is no external leak. So, change the oil, replace the thermostat and coolant and you're good to go.

Wow, this was creative, from personal experience? Or did you wake up with your Rosie sunglasses after dreaming of winning mega millions tonight?



I hope it's as easy as sandroad outlined, but if it's not, I'd search for a used 4.7 (vendors here?) For a swap. It may be more cost effective.

 

[Julian Stead]

The thermostat is one of the more common reasons why you get head gasket/engine failures. If you stopped the engine due to steam bellowing out from under the bonnet then it could of come out of the expansion tank, and if this is where the coolant was lost, I would expect it to be noticeable if this was the case. If the thermostat is to blame you still have to find where the excess pressure and coolant escaped. If the rad cap done its job and dumped the pressure before damage then happy days.

 

[ponytl]

you can check some of my threads I've swapped / replaced a couple engines... if you do it yourself you can swap in a 100k engine for less than 1k which includes all the stuff you would want to do TB WP ect... I'd rather swap an engine than do a head gasket

 

[TeCKis300]

^that. 2UZ's are a commodity motor and a dime a dozen as they were used in so many models. I personally would always resort to a nice used motor, rather than repairing any motor that requires open heart surgery. They can be had for cheap, with a startup warranty. And the labor can practically be done in a weekend, if not a day for an experienced mechanic.

Car-Part.com--Used Auto Parts Market

 

[ton504]

Fyi you don't have to be blowing smoke to have a blown HG. Get you hands on a combustion leak tester. Basically it tests the coolant for exhaust gas.

I bought my 100 for a blown HG. PO's wife overheated it majorly after the heater ts cracked. It ran fine until it warmed up then started to miss. It never smoked. But it tested positive for the test.

I bought an engine out of a LX with 120k. Timing belt and spark plugs were recently done before whatever happened to the donor truck. Paid 1600 shipped.

 

[savirc]

I second failed t-stat. That or air in the water passages, needing burp. Either way this is the easiest way out and easy to mark off the list of possibilities, so I would start there.

I know this is unrelated but the jeep 4.0 H.O. would overheat when not burped or faulty t-stats