Diagnosing Engine after Overheating

[Curran]

Question: How do you diagnose an engine that won’t start after it overheated?

The truck is a 1990 22RE 4x4, 5 speed manual w/ approx 160,000 miles. I installed a new Engnbldr RV Head / with 270 cam; timing chain and radiator approximately 30,000 miles ago. The starter will currently spin but that is the only sound I’m getting out of it.

Thanks,

[KLF]

Fuel. Spark. Air. Gotta have them all.

Have you checked to see if there are any codes stored in the ECU?

[RVBtruck]

When you say the starter spins yopu mean the engine is turning over right?

[Curran]

Originally Posted by RVBtruck

When you say the starter spins yopu mean the engine is turning over right?

No. It doesn't sound like like it's trying to turn over. I'm just getting a noise that sounds like the revving of the starter motor.

[Tools R Us]

Originally Posted by Curran

No. It doesn't sound like like it's trying to turn over. I'm just getting a noise that sounds like the revving of the starter motor.

Are the belts. fan turning when the starter is engaged? If not maybe a broken starter drive, very rare on a Toyota and unlikely to be caused by overheating.

Define "overheated"? Low or no compression will cause the motor to spin easily, almost sound like the starter is only turning. This can be caused by severe overheating, warped head, blown headgasket, rings lost their tension, holes melted in pistons, etc. Usually accompanied with things like melted spark plug boots, etc. and easily confirmed with a compression test.

[Curran]

Originally Posted by Tools R Us

Define "overheated"?

Driving home from work late Tuesday night, (50 mile commute at 70 mph) I started to notice a bit of smoke from the tail pipe. It was cold and snowy so I didn't think much of it. Then less then a minute later I noticed steam coming up from between the driver's side fender and hood. I looked down at the temperature gage and it was pegged beyond the red! So I shifted into neutral and coasted to the next exit. As I was taking the exit ramp the engine shut down and would not restart after it cooled. Still had Coolant in the over flow tank -- no bubbles apparent. And the oil showed no visible signs of contamination.

Originally Posted by Tools R Us

Low or no compression will cause the motor to spin easily, almost sound like the starter is only turning. This can be caused by severe overheating, warped head, blown headgasket, rings lost their tension, holes melted in pistons, etc. Usually accompanied with things like melted spark plug boots, etc. and easily confirmed with a compression test.

Sounds like I need to start reading about engine swaps. What happened to the "I'm going to get sick and puke" smiley face?

[RVBtruck]

sounds like a possible starter yet, Check to see if it is turning the engine. If not take it out and try to turn the engine over by hand to see if it is seized.

[Tools R Us]

Correct, first confirm that it's turning, if so pull the plugs and compression test to see what you have.

[Curran]

Update:
OK, I was wrong the engine is turning over. Just wont start. I pulled the plugs. The plugs in cylinders 1, 2 and 3 looked normal for about 30K miles. The plug from # 4 was a black oily mess.



Is it worth buying a compression tester at this point? Next steps?

CJ

[KLF]

I personally don't like compression testers, they only tell you that you have a problem, but don't tell you WHERE the problem is. I prefer leakdown testing, if done properly it will tell you exactly where you have the leak in the cylinder. But, to be really accurate the engine needs to be at operating temperature, which you can't do.

Given the look of that plug, my guess is you have something seriously wrong in the bottom end. The result is, it doesn't really matter, the engine needs to come out and come apart.

Does this truck have a SAS? Would make it easier to at least drop the pan and take a peek up inside.

[Curran]

Originally Posted by KLF

Given the look of that plug, my guess is you have something seriously wrong in the bottom end. The result is, it doesn't really matter, the engine needs to come out and come apart.

Does this truck have a SAS? Would make it easier to at least drop the pan and take a peek up inside.

There is a SAS in this truck's future. Right now though it is a daily 100 mile commuter -- IFS still intact.

[Tools R Us]

#4 is oil fouled, but they all look very worn, old, it could have just failed. I would run a quick compression test.

[Curran]

Kevin,
When you say "it could have just failed," what are you referring to?

Thanks,
CJ

[Tools R Us]

Originally Posted by Curran

Kevin,
When you say "it could have just failed," what are you referring to?

Thanks,
CJ

The fouled plug in your picture, #4.

[Curran]

I thought that the oil fouled plug would have been the result of a failure elsewhere, not the failure itself. Perhaps I’m misunderstanding you.

[Texx]

Compression testers are under 10 bucks. Takes maybe 20 minutes to do the test, it may answer alot of questions. Are you getting fuel? New plugs are cheap. I'd say it's possible you've burnt a valve or broken a ring. If you get it running and the exhaust is white with a sweet smell, you need to start with a head gasket. Post your compression numbers. No need to immediately suspect something in the bottom of the engine. Check for spark by grounding a plug against the block while cranking...

[Tools R Us]

Originally Posted by Curran

I thought that the oil fouled plug would have been the result of a failure elsewhere, not the failure itself. Perhaps I’m misunderstanding you.

Judging from what I can see in the picture, the plugs look like they have a lot of miles, wear on them. High mileage plugs can fail or it could be fouled from other problems. Knowing the compression of that cylinder compared to the others would shed more light.

[Curran]

Compression test on the cold engine:

Cylinder PSI
#1 0
#2 34
#3 30
#4 45

I was expecting #4 to be the lowest given the fouling on the plug.

To add a bit of background info: The plugs, head gasket, timing chain, injectors and radiator were all replaced about 30,000 miles ago when I installed the Engnbldr RV head. The head was installed with ARP studs.

[2ndGenToyotaFan]

0 on #1 seems like an open valve, but the rest are wayyyyyyy low too. Something's wrong.

[Curran]

Agreed.

[Texx]

Might as well go ahead and pull the head...it's really not a terrific amount of work, you will have to do it anyway sounds like. Then, a physical inspection of the head, piston tops, and valves should tell the tale..

[Tools R Us]

The next thing I would do is check the valve adjustment, if they are tight the compression may come up when adjusted.

But that's probably a long shot, my guess is that it got really hot cooking the rings. When the rings get extremely overheated the temper is lost, then they don't have any spring tension holding them tight to the cylinder wall. Motors that get that hot most of the time have other issues, warped head, piston issues, etc.

[hobiesbestfriend]

so was there an answer to this ever? What was the problem?

[Curran]

On the advice of the two mechanic buddies, I just swaped in a new long block. I plan on conducting an autopsy of the old engine and head when the weather gets better. It looks like the headgasket of the old engine bit the dust, but I can't claim if that was a cause or result at this point.