tora117

Hello guys, this is my first thread in CL and unfortunately it is not very exciting.

I will try and keep the story as brief as possible.

A few months ago my 94' SC3 overheated pretty badly while at a light. I haven't had any overheating problems up until that point, however my temperature gauge has never worked since I bought the car . Anyways, something must have broke because the coolant got so hot it blew a hole in the top of the radiator. I moved off the road and shut the car off (it didn't quit on its own so that's good i suppose). Came back in the middle of the night, plugged the radiator with some puddy and filled it with coolant so I could get to a shop. Shop fixed the radiator and got the car back a few days later

Unfortunately, since getting the radiator replaced and any leaks fixed, the car still overheats. I have done a compression test and leak down test to see if I have a blown headgasket. Compression test came back ok (I think) except for #3&4. Leak down test was all out of the crankcase and was also ok. Nothing in the oil and exhaust.

Compression Test (dry) [wet]:
Cyl 1: (169)
Cyl 2: (168)
Cyl 3: (130) [162]
Cyl 4: (151) [175]
Cyl 5: (160) [167]
Cyl 6: (160) [172]

Leak Down:
Cyl 1: 76/80
Cyl 2: 76/80
Cyl 3: 78/80
Cyl 4: 77/80
Cyl 5: 77/80
Cyl 6: 78/80

TL;DR Idiot with no temp gauge doesn't know car is overheating until he blows his radiator. does it two more times

Im a student right now and im worried that I have a lot of damage to my motor. I am going to be tearing it apart and pulling the head this week and need to know what to look for. I know that the head will probably need to be surfaced/decked, but would I need a valve job? I have heard that when you overheat your motor your clearances can get all fouled up. Am I better off just trying to find a new head? New engine?
I had planned on doing TT hg + studs and full service so I can boost it when I have time/money. Right now that's still the plan, but I need some advice on how to move forward with this motor. I love the 2jz and the SC platform so hopefully I can get my baby back on the road soon.

Any advice/help is greatly appreciated!

Thanks,
Ethan

Ali SC3

iTrader: (10)

The numbers don't look terrible, the 20% leakdown is a little high but it is pretty even across all the cylinders.
The compression looks a little low but once again pretty even.

It could be the gauge you are using is just off, or you have some ring wear since you said it came out the crank case mostly.
IF you stick your finger in the exhuast ports on the leakdown and aren't feeling much, then valves are probably ok since they would be the first to leak on the leakdown from overheating.

If there is no coolant milkshake, or other signs of a blown heagasket, make sure the radiator isn't plugged and the coolant is actually circulating, look for flow in radiator with the cap off (don't remove it while hot.. start engine when cold with cap off) and also check thermostat.
when was the last time the waterpump was replaced? that would let it overheat also. You have to have a pretty solid overheat to mess stuff up. The radiator is the weakest link, so if you shut it off soon after that went, it might be alright.
I would expect some type of leak/BHG to show up on just a few cylinders, but your numbers are pretty consistent, even cyl 3 once you did the wet test isn't that unreasonable (its not perfect either though).

RXRodger

iTrader: (2)

The head is probably good. I have had a couple of these overheat badly and just got by with a head gasket change. Just completed one a couple of weeks back. Replace the radiator, you can buy them for $80 or $90 off rockauto. Fill it with coolant, bleed the air off, see what it does. If it blows the coolant out, then you probably are in for a head gasket change. The compression/leak down looks ok but sometimes that can throw you off and it can still have a bad hg. But, try it first and see if you can keep coolant in it. As Ali said, what about the water pump? If it is circulating fluid it probably is still ok.

My bet is you need a hg, but hopefully not. If you end up pulling the head, if it were me I would go ahead and do a head rebuild just because of all the trouble it is to pull it. But, limited on funds, I might take a chance. Just understand you are operating with 20+ year old valve seals so its just a matter of time before they leak.

tora117

Sorry for the delay. I drained the fluids last night and the oil was a nice chocolate milk color YAY. Im planning on sending the head of to get decked and cleaned. I will be shocked if there isn't some significant warpage due to how badly it was overheated but I won't know till I pull it. Im assuming that the only big work will be fixing all the valve lash from the warpage but again im not sure.
GTE Headgasket and arp studs is on the way plus all new cooling components. Considering its still in the upper 90s here in texas im not too mad that im having to do all this before winter as the car would still be undrivable.

Ali SC3

iTrader: (10)

Not to discourage you but if you didn't fix your temp gauge to work after however long, you might want to rethink going na-t as it is not easy and it is a ton of work and figuring things out.
Also, when its overheated to that degree, valve lash isn't the big issue.
The real questions are:
1) how badly is the head warped? if its .020 or more than just look for a new head
2) did you burn any valves up in the process?
3) did it get hot enough to cause pitting on the block?

If that compression or leakdown test was after the heating, then maybe the valves didn't get burned up and just need a cleaning.
checking and setting the valve lash isn't hard or a big deal, and it probably will be fine if you put them all back in how they came out.

I would take the head off the block and inspect the block surface, and the shop can tell you how badly warped the head is.
You will see what blew out, if it was the gasket or there is a chance you could have cracked a passage in the head if it got really hot.
If there is an issue with the block, or the head is really super warped, I would look towards a replacement engine then.

best case scenario the block surface looks fine (should be smooth to your fingernail going across it) and you just blew the gasket between 3 and 4, you shave .01 off the head, and put it back together with all the maintenance parts.
And fix your coolant temp gauge of course.

tora117

Both of the tests were after the car was parked so that makes me feel a bit better.

In regards to the block, if after a good cleaning it measures good with a straightedge, would it be ok to go back together? My goal when reassembling it is so I don't have to open it again for NA-T. I have heard that even with a decked head, if there is even a slight warpage in the block you could have major problems when boosting. I really don't want to pull the motor but if I really need to get it honed and surfaced at a machine shop I will. I suppose it will depend on how the surface and cylinder walls look when I pull it apart like you said.

As far as the temp gauge goes I don't really know why I didn't fix it. I suppose since I hadn't had any problems with the car getting hot when the gauge still functioned, I just didn't worry about it. I def wont make that mistake again. Now that the car is apart I will go ahead and replace both temp sensors and hopefully I don't have to rebuild the gauge cluster again.

I haven't had much time the past couple days to work on the car but I will try to get the head off either this afternoon or tomorrow morning.

Ali SC3

iTrader: (10)

Pitting will show up like small circles in the block surface or areas where the metal got too hot. If you can feel it with your fingernail going over it then you may have issues, especially if its in an area that the gasket will seal on.
If you just has one overheat and shut down chances are it is fine, but you never really know until you look at it when you have had several overheats. Usually it doesn't need work on the block, but if it does then that is a lot bigger job then the head and might cost less to find another engine or put it towards a swap. If you see some problem areas after you open it post them up.

tora117

Thanks for the info, I will look out for that. Fingers crossed there are no issues.

RXRodger

iTrader: (2)

Almost all of the blocks have some pitting. I have had one that was really bad and I cleaned it up and clamped on a rebuilt head and it sealed. Not optimum but it worked. Just be really careful cleaning the block, the block surface is actually harder to get fully cleaned up than the head. Use a block of wood and scotchbrite after completely scraping with a razor blade. Don’t use anything that can scratch the surface, in other words be careful with the blade.

tora117

Well a cold front came through and rained me out (working outside) so I didnt manage to get the head off this weekend. I have just about everything off except the cam gears and cams. Unfortunately I already took the timing belt and crank pulley off so Im gonna have to just wedge a wrench onto the cam.

The good news is this is probably not the original motor. The valvetrain looks brand freaking new. There is some discoloration on cylinders 1-3 but everything else looks like it has MAYBE 40-60k miles (car has 170k). Im excited for what I find when I pull the head off now!

My goal with this motor is around 600 reliably. Could I get away with using the stock valves? Im planning on doing springs and retainers and I can throw cams in later. Like I have said many times I dont want to have to crack open this motor again but I also dont want to have to dump $600 into new valves and machine work. I couldnt find any good information on what the stock valves are good for. I imagine they would start to bend past 800 but idk.

Edit: Stock retainers or BC steel?

RXRodger

iTrader: (2)

Cam gears: You should be using a wrench on the cast in hex on the cams regardless of whether you have removed the belt or not so you are still fine.

Retainers: What are you planning to do with the car? I would think you are fine with stock retainers unless you are planning on a high rev situation. Valves same.

tora117

Well I got the head off last night and got the deck cleaned off with some wd40 and green scotch bright.

Here are some pictures I took in the sunlight today. There is still some gasket material left but what I could only assume is some pretty decent pitting as well.

Not really sure if I could get away with a headgasket and copper spray until I build the motor or if I should just go ahead and get the block done.

RXRodger

iTrader: (2)

That actually looks pretty decent. I would take a razor blade and scrape any remaining gasket material off, make sure you don't scratch/score the surface so just be careful, then scotch bright wrapped in a straight wooden block again. You know you can pull the two dowels to get that area better, right? When that's all done should be good to go. Use the Toyota OEM gasket, those seem to be the best.