[fufu1234]

1990 SR5 4x4 V6.

I’ve been trying to figure out why my truck is hesitating so badly when cold. A mechanic at Toyota today told me that it could be due to an air lock in the coolant system. He said that I should run the truck for a while with the radiator cap off, fill it up, then bleed any air off that might be at the top of the engine. He said that there was a valve somewhere there… but I’m not sure what he’s talking about.

Has anyone encountered this problem before? An air lock in the coolant system? If so, where is the bleeder valve that will allow me to get rid of this air? Or is there some other way of doing this?

Thanks.

 

[rogerman]

ive read alot about this. heres what you do. park your truck on an incline so that the front end is higher. then remove the rad cap and start the engine. some people claim their radiators become volcanoes ect. so be careful and have lots of extra coolant.

 

[fufu1234]

Yea so I ended up changing the fluid out. Drained the old stuff out and filled the rad with new. Started the truck up and let in run for a bit. Then all of a sudden hot steam and water started bursting out of the rad cap. The engine was obviously getting hot, but the idle wasn’t coming down, and there was no heat coming out of the interior heater. The engine also had a pretty severe hesitation. I’m assuming that no fluid was getting into the engine for some reason?

So I shut it down and took a hose off that goes through the firewall. It was dry. Very strange. I ended up poring almost 4L of coolant down that pipe. I started it again and the idle came down and the hesitation went away (and it stopped spewing hot steam).

I set out here to try and figure out why my truck has a hesitation (especially when cold). The guy at Toyota told me it’s because I could have an air lock. When I had the really severe air lock (no coolant in the engine at all) it had a wicked hesitation. What’s going on there (I'm assuming it has something to do with the cold start injector)? Could it be that my trucks hesitation is caused by a small air lock?

 

[Sidney]

You got lots of air trapped in there.

Make sure you use 50% Toyota long life red low silicates radiator coolant to reduce corrosion build up on the tiny water bypass passages found in the aluminum cylinder head and preferably 50% distilled water,rain water or snow water.

I would pour the mixed coolant & water combination into the thermostat hole until full then install new stat and stat cover/hose tighten up.Start the truck on an incline or car ramps and start pouring mixed coolant & water combo into radiatior almost to the neck wait for stat to open which is about 10 minutes of idling then turn your heater on to high and hot (as well as your back seat heater controls for those with 4-Runners) and rev the engine back and forth but not too high.Re-top the coolant and continue to do so for one or more stat cycles.

Finally turn the heater control from hot to cold repeatedly and from high to low and place about half mixed coolant & water into overflow bottle and place stat cap back on,take for a test drive.Once engine has cooled off check the rad level and overflow bottle.

Sidney® ™
E-mail:[email protected]
Dartmouth,Nova Scotia
Canada
1985 Toyota 4-Runner,solid front straight axle,factory cruise control,sunroof,22R-E,W56,RN60LV-MSEK,rusted rear step/towing chrome bumper with 252 000 KM

 

[Vicoor]

Sounds like a blown head gsk. Likely to have a misfire to to this causing your drivability problem

 

[fufu1234]

There's also a strong smell of un-burnt gas coming from the pipe. Does that go with the head gasket problem? It actually had a compression test done not long ago… I’ll have to pull the results out.

 

[Sidney]

There's also a strong smell of un-burnt gas coming from the pipe. Does that go with the head gasket problem? It actually had a compression test done not long ago… I’ll have to pull the results out.

I don't like compression tests I prefer leak down tests and fluid analysis test which any Caterpillar dealers sells the kits for only $15-20 at their parts dept and the results will be obtained in a day from their lab.

Sidney® ™
Repairs tv's,vcr's,home/car audio out of my home
E-mail:[email protected]
Dartmouth,Nova Scotia
Canada
1985 Toyota 4-Runner,solid front straight axle,factory cruise control,sunroof,22R-E,W56,RN60LV-MSEK,rusted rear step/towing chrome bumper with 252 000 KM