OK In installed a rebuilt 3.0 today. It ran great for the initial test drives and we worked out some leaks but nothing huge and it ran fine, lots of good power actually.

I drove home from the shop (about 1/2 hour) and about half way the temp gauge started to come up to a max of about 1/8th past half and when I would stop at a light it would die. The odd time it would idle it was at 300-400 RPM. I got it home but had to stop and let it cool down a few times (once right in the ghetto :8, I lived though).

While I was driving the temp gauge would go from normal to high and back down again and then to high enough that I just shut it down. The temp was all over the place but never low. Also, the longer I drove it the more the oil pressure seemed to drop but I never reved it over 3k so I'm thinking this may be unrelated or a leak somewhere, maybe not.

I'm thinking an airlock or a bad thermostat would cause the heat problem but why would it always be wanting to die when at idle? It was acting like there was an air leak in between the AFM and TB but I think that area is fine. How do I clear this little glitch? I will take a good look at it tommorrow in the light to see if there is anything obvious. Am I missing anything here?

 

i'd never trust a factory gauge, before you go tearing things apart i'd put an aftermarket autometer gauge on there and REALLY know what the temperature is. They dumb down the factory gauges so bad. Hope you get things figured out. You could try using a heavier weight oil and see if you get better oil pressure. You can also take the thermostat out and test it with hot water on your stove with a thermometer handy.

 

I tried burping the coolant this morning and then took it out for a test drive. Here is what I've noticed:

Once completely warm the engine will seem to start to overheat (needle never goes into the red or within 1/4" of it). When it gets hotter the engine wants to die at idle. However if you keep the RPMs up above 2500 the temp seems to stay around normal, let it idle and the needle goes up and the idle goes down till it wants to die. Hit the throttle and the temp drops back down and it wants to idle properly.

I’m pretty sure the temp and idle problem are related cause when the temp goes down the idle level out properly. I haven’t changed the t-stat yet but could that be the problem?

 

In one of my rebuilds the bonehead who did it put the head gaskets on the wrong side.

There's a port on one side that's not on the other and if the head gaskets are reversed the port is blocked.


The symptoms were exactly as you describe.


I'm pretty sure the portion of the HG's that are labeled sticks out from the block and can be seen externally.

 

Almost every car I have ever owned has done that to me at one point or another and it was always the same think my Thermostat was going out and not performing properly. It sounds like yours is sticking a little and so when you rev up a little and get the RPM's going your basically manually helping yoru T-stat open. Replace that before you do anything else because chances are that's it and it's really cheap and easy to replace. Good luck.

 

I agree with this

 

If at first the thermostat does not fix your problem, then check the radiator. Have you put fix-a-leak in your radiator? Have you replaced your radiator with one from a yard? All the yards will put fix-a-leak in their radiators to stop any leakage and send them out, but all that fix-a-leak crap does is stop flow. Your radiator will not work if it does not flow very well. I think our's needs to flow around 6 gallons a minute or something like that. You can't really go below stock flow in the radiator or you will begin to overheat. Lord knows our motors run on the edge of hot in stock form as it is. Depending on what happened to your other engine, a faulty radiator can be the cause for ruining an engine. Definitely check your radiator flow before you tear into an engine to check headgaskets if you dont see the HG marker sticking out to let you know that it was installed correctly. I changed my radiator when I installed my motor and replaced with a new water pump and timing belt. All things worth it in the long run. Rad only cost $200 from aftermarket Toyota OEM quality parts place.

O

 

2X for the radiator. new motor=new radiator.

 

The rad was flow and pressure tested when I had a leak fixed about a month ago no fix a leak was used. I guess I could pick up a new one though. Everything else on the engine is new, and the old one runs fine the one I installed has P&P heads with OS SS valves and the bottom end Blue printed.

Where on the gasket is the mark usually? Its been months since I installed it so I don't remimber.

 

I installed a 180 t-stat in it and that helped a bit but it still overheats. I talked to a local mechanic who has build a few toy engines for himself and he thinks I need a high performance thermostat that will flow more fluid when at temp at lower RPM ranges. I'm just using a standard parts store brand now, will the Toyota one flow more coolant better? Does any performance T-stat company make a thermostat for the 3.0?

 

hmm i am goig nto jump in on this because today i started to heave a very similar problem. except mine would never get so hot that it wouldnt idle good. I have an 87 4 runner with a 22re and about 3000 miles on a rebuild. the previous owner did the rebuild so i dont know idf the thermo is new or not. At cruising rpms the temp will increase slightly to abotu 65 percent when i usually run 40 to 45 percent on the gauge. But if i accelerate slightly it will drop back down. And high rpms still are fien and it stays cool. I think i am having a thermostat problems just as it sounds you are. What i alwasy say abotu cheap parts liek thermostats is if it doesnt work the first time try it again because if they cost next to nothign abotu the same tiem goes into making them. IT deosnt make sense that you need a performance thermostat if you havent made signifigant upgrades to your engine. I rebuild with slightly better performance shoudl not affect temperatures by very much.

 

I installed a Toyota stat and it made no diff. I'm ruling out thermostat.

 

Shot in the dark... but what's your timing look like?

Also, any codes?

 

I'm going to bet that you have more than one problem going on here. For now, ignore the idle problem if possible. When the idle drops too low the alternator's output drops and the temperature gauge rises about 2-3mm from the lower voltage. So, you need to account for that throwing things off.

Also, you need to verify that the headgaskets have been installed on the correct side of the engine. I will attempt to get a photo of what you need to look for. But, essentially you're looking for a large piece of headgasket to be sticking out of the LH bank at the inner forward edge. On the RH side at the inner rear you shouldn't have any "extra" headgasket sticking out. If these are switched then the coolant will not flow properly and you will have overheating issues immediately.

 

Timing is 10 deg.

A pic of the HG would be sweet.

 

I saw where one guy had gotten two headgaskets for the right side in his kit instead of a left and a right and didn't notice during the install. He had the same overheating problem. I've even heard of dealer mechanics getting them on backwards.

 

WooHoo! She runs and she runs cool. It was the fan clutch. I also drilled a couple holes in the t-stat. It takes a little longer to heat up but the temp needle is bang on all the time now. I went for a good 45min drive with no problems. Man am I happy. I'm gonna put off the electric fan till next summer. thanks for all the help guys.