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Discussion Starter · #1 ·
Periodically, the idle will bounce up to 1500-1700rpm then fall to normal idle, over and over again. I also noticed that the temp starts to go up. It seems as long as the temp is elevated the problem persists. After driving a couple of miles and the temp goes down, the problem disappears. Ant thoughts?

Thanks.
 

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Most likely air in your cooling system. you need to purge that air out. Jack-up the front end as high as you can (preferably on ramps)remove the radiator cap and crank it up and let it run until the thermostat opens. Make sure the radiator stays full. After it has ran with the thermostat open, that will probably cure the issue. Let your truck back down and make sure it is still topped off with water.
 

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Listen to Sassee, you will soon have your truck fixed.

 

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Discussion Starter · #5 ·
Took a while to take a look as I was out of town... However, Old Timer was right on the money - air in the cooling system. Actually, the radiator was down almost a gallon. Luckily it's been cold in Seattle so no over heating. Which leads to my next question...

Where did the coolant go? I had a new thermostat, cap and flush done about 6-7 months ago. Also had a block check done (no issues) as I was loosing coolant then. Thought the new thermostat/cap fixed it - not so. No obvious leaks/puddles. There is no sign of coolant in the oil. No excessive white smoke. Seems to match other cars in the morning, nothing once it warms up. Any thoughts???
 

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Red Dragon said:
Where did the coolant go? No obvious leaks/puddles. There is no sign of coolant in the oil. No excessive white smoke. Seems to match other cars in the morning, nothing once it warms up. Any thoughts???
Same thing going on with my rig.

Nothing obvious to show where the coolant is going.

I can only guess that it is going out the tailpipe, (head gasket), but doing so, so slowly that it isn't noticeable.

It only drops about a pint in 80 miles of driving. And since I never put more than about 50 miles on it at a time, I just check the coolant before every time that I drive it.

And I keep a constant eye on the temp guage.

And 5 gallons of water in the back of the vehicle at all times.

Maybe when it finally gets hot for that week of summer that we have, it'll be more of a problem. (REALLY getting sick and tired of 31 to 43 degrees and rain rain rain...)
 

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Unless you bleed the coolant system you can continue to add coolant to the radiator every time you drive it for a while until all the air bubbles make their way out. I'm lazy and don't bleed my systems out, I just open the hood every morning and fill the radiator until the level stops dropping. Sometimes this take a couple weeks. You may not have a leak or be losing any coolant at all.
 

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However, Old Timer was right on the money - air in the cooling system
OLD TIMER!!! I resemble that remark!
 

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********** said:
Unless you bleed the coolant system you can continue to add coolant to the radiator every time you drive it for a while until all the air bubbles make their way out. I'm lazy and don't bleed my systems out, I just open the hood every morning and fill the radiator until the level stops dropping. Sometimes this take a couple weeks. You may not have a leak or be losing any coolant at all.
I recently had the rad out.

So it sounds like you could very well be correct.

I'll try to actually burp it, the first time we have a day without torrential rains and 30 degree weather, again.

Not difficult to find a hill around here, that I can run the front up on. LOL
 

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Does anyone have a bleeder valve on the t-stat housing? (like mine) this looks like a great bleeder spot to get the air out. If you fear coolant lose pull plugs & check for one that looks too clean, then do compression test.

~psguardian
 

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I've got a bleeder on my 1988 trooper. It didn't come that way. I pulled the whole housing off a 1995 rodeo 4cyl. Ever since I installed it I have yet to use it. it seems like the ones with the bleeders don't trap air like the originals do.

Selador, I once thought I had a tiny head gasket leak for many years because I had to keep adding fluid to the overflow. Turned out the over flow bottle was rotten on the bottom and dripping ever so slightly. LOL
 

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psguardian said:
Does anyone have a bleeder valve on the t-stat housing? (like mine) this looks like a great bleeder spot to get the air out. If you fear coolant lose pull plugs & check for one that looks too clean, then do compression test.

~psguardian
I just put new plugs in, so it'll probably be a while before I see any real differences in the plugs.

Having lower compression on just the #2 cylinder is what I am basing my head gasket, or cracked head assumption on.

rollintroopers said:
I've got a bleeder on my 1988 trooper. It didn't come that way. I pulled the whole housing off a 1995 rodeo 4cyl. Ever since I installed it I have yet to use it. it seems like the ones with the bleeders don't trap air like the originals do.

Selador, I once thought I had a tiny head gasket leak for many years because I had to keep adding fluid to the overflow. Turned out the over flow bottle was rotten on the bottom and dripping ever so slightly. LOL
I'm going to have to look for one of those.

Last I looked, my overflow bottle has stayed exactly where I filled it up to. Never changes.

Now that I wrote that, I am thinking it would probably be a good idea for me to check out the tubing to that, and make sure it isn't clogged somehow.
 

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Discussion Starter · #14 ·
Sassee, call me a rookie. I took a quick look and thought that your ID was Old Timer - but then I noticed that pretty much everyone's said Old Timer. Ooohh, I get it.

Hmm, too clean spark plugs. I did take mine out and 1 and 2 were darn near spotless while 3 and 4 looked like I would expect, some carbon. I also found this site...

http://www.rebuiltautoengines.com/isuzu-articles.html

Take a look at the "Cylinder Head Bolt Caution On Isuzu 2.6L Engines" section.

I am guessing I am looking at a new head gasket. Would it be worth my while to replace the head with an aftermarket head (approx $300)?
 

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Well, I think I probably found my coolant 'leak'.

I recently had this thing stripped down to the timing belt.

Removed the radiator.

Took the water pump off and checked it out.

Put it all back together, and got it running again.

Anyone want to guess what the leak probably is ?
 

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$10 leaking @ water pump gasket.
 
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