Ok before I ask if there is a good Thermostat DIY somewhere around here, I am hoping you're going to to tell me it's NOT the TStat OR the LIM.

Van has 144k miles on it. It's been well maintained (see my other posts). I have had it since new (7 miles). The LIM was done preventively at about 75k miles (5 years ago).

Two to three years ago it started using/leaking etc coolant at a very slow rate. I would estimate somewhere in the 8-10 fl oz per 3-4 month range. As time has gone on it has been progressively using more. Now it is about 12-14 fl oz in about a month or 6 weeks. My "low coolant" indicator came on the other night. It had been a while since I added any coolant mix. 3-4 months anyway. It took about 1/2 gallon (US). There has been no "real" visible leak,up to now. I noticed yesterday when I was under it doing an oil change, that there was a "film" on the bottom of the trans pan. I followed the trail as best I could and it led me to the rear of the engine near the drivers front wheel. It was a small drop of coolant. (I tasted it). Don't try this at home... From the top of the engine looking in, I followed the upper radiator hose to the thermostat housing "pipe". It is very difficult to see in there. I took a few pix. You can see them here.

https://picasaweb.google.com/103956146819641847893/VentureCoolantLeak?authkey=Gv1sRgCP2my5_rx-3WVw&feat=directlink

It looks like there is a little pool of coolant sitting near or under the thermostat housing that pools on top of where the transaxle bell housing meets the engine block. It's very hard to to see in the pix. Some of what looks to be damp, is actually shadow. This pool I believe runs down the back of the engine/trans, and then is blown on top the trans pan and undercarriage.

The van runs great, I want to keep it for the next 9 years. There is no coolant in the oil, or oil in the coolant. Unless the fix is fairly easy, the leak is still small enough that I am not going to bother with it until it becomes a large leak. The car runs cool even in the hot summer pulling a load. The only issue is the leak and that I have to add coolant every once in a while.

So. What are my likely candidates? Tstat housing/gasket? Other gasket? corroded tstat housing pipe? What else is in there?

Any thoughts, comments or suggestions welcome.

Thanks

P

Hi P-

I'm thinkin' it might be the throttle body coolant hose(s) that's the source of the leak?

Kornjulio, Tnx for the quick reply.

Now that's something I never even considered. I seem to remember reading about the fact that coolant does make its way up to the TB. Are these hose(s) prone to leaking like this? I'll have to take a look for them tomorrow during daylight. If it is the hoses, are they relatively easy to replace?

Thanks.

Paul...

I'm not aware of them being prone to leaking, but nothing shocks me anymore. I think they're easy to replace; but my biggest concern would be if they're formed hoses or not. I can't remember, but RockAuto does show an ACDelco part for one of the hoses-so you may not be able to use a section of bulk hose to replace it.

They're just held on by those spring clamps. Worst part will be getting a good bite on the little ears to open them up.

I'd start by removing the throttle body. Your leak is either going to be at those hoses; and if it's not, now with the TB removed you're going to get a good look at what's going on down there & be able to figure it out. Worst case is you need a new TB gasket & hoses. A fair trade for being able to get a clear view down there.

Edited to add: Let me be clear: I don't think you can replace the hoses w/out removing the TB. They're just too short & hidden to work with them. You have to slip the clamps back, then unbolt the TB. As you remove the TB, you then pull it off the hose. Know what I mean?

Is the TB removal self expanatory? Just get in there and have at it? Or is there a sequence? Any tips etc? Tnx
P.

i would also check that small hose going to throttle body as he sugjested.

Is the TB removal self expanatory? Just get in there and have at it? Or is there a sequence? Any tips etc? Tnx
P.

Worst past will be removing the hoses at the bottom as I covered. Other than that, it's pretty much remove what you see, unbolt the thing, and if it's adhered to the rest of the manifold, a light tap with a mallet should break it free.

TB can stay on to replace the short 1" hoses on mine. Pull the nut holding the metal tubing in place, pull the pipe outta the pump, loosen hose clamps, remove HC connection, pull free.

NOW, I didnt see what year you have, but I would suspect that you do have a LIM leak, and I WOULD get it fixed before you need a new engine.

BTW, I have been thru several thermostats lately and I finally got a Stant Super Stat and it seems to be the best of the bunch so far. I dont see how the thermostat housing could be leaking on you without provocation. As far as the small TB coolant lines, dont see that either, but you never know.......

ALSO, the LIM thing can be done over the weekend, one of the first things I did with my new JY engine.......... could be what did in the old one before I got the thing........

The pipe that exits the intake manifold (underneath the throttle assembly) is about 1/2 inch steel and uses an O ring to seal to the manifold. This pipe feeds coolant up the heater hose on the firewall. The O ring wears and it leaks. Dumps antifreeze right down behind the thermostat.

Update:

No change in frequency of having to add coolant to the overflow. Still about every 8-10 weeks and it is about 2-4 cups. But a week ago, the Coolant Level Low light came on. usually when this happens, I add 2-4 cups to the dry overflow, and all is well. This time I still get an intermittent Coolant Level Low.

2000 Venture now has 150 k on it. I Never flushed the cooling system. Only changed the fluid at about 75k approx 6 years ago. when LIM was done (by a good, trustworthy and talented mechanic (not me)).

There are no "visible" leaks to speak of. The car runs fine. With the cooler autumn temps, it seems to be running cooler in certain instances. It is really acting like the TStat is stuck either full or partially open, I get "adequate" heat in the cabin.

I have an ECT sensor reading via OBDII that I have been monitoring. Around town in ambient temp of about 60 deg F, it runs between 170 & 180. Never higher until I stop and idle for 5-10 mins, then it will go up to 205 or so. Driving again, or turning AC on, (starts the fans), and it will cool down fine.

If I go on the highway, it gets to 186 and stays there for 5 or 10 mins or so miles and then climbs to 192-196 and stays until I get off the highway, then within a few miles it is back to the low 180s. Occasionally with a long idle after driving it will climb to 210-215. But again, it will cool right down to 185 as soon as I put AC on or start driving.

I noticed the level in the overflow had not changed since I added coolant a few days ago. I got a new radiator cap and blew out the line from the filler to the overflow.

When I took the rad cap off, there was "crud", Brown, rust colored, pasty, crud on it and the filler neck. The coolant was a few inches low in the radiator (did not appear to be below the CLL sensor). The coolant was clean and green (no mush, or particles in it.) The level was high enough that I couldn't see any of the rad tubes through the coolant. There was just this crud on the cap and neck. I added coolant directly to the radiator and filled it to the overflow tube. The CLL light has not come on since adding coolant and changing rad cap.

Now for the questions.

1. How foes a backyard DIY-er do a rad flush these days? Is it like the old days? Buy a "T" kit, break a heater hose, install "T" use garden hose, replace coolant etc.?

I don't have access to one of those "environmentally sound" coolant flusher/filter machines. Should I just pay someone that has one to do it?

2. If I decide to do the Tstat. (I will probably do the TB hoses and check that leaky sensor (whatever it is (see pix above)). What is involved? It looks pretty buried under the TB and intake.

3. Is there a DIY floating around. I've done several TStats before, but they all have been very accessible.

4. What are the chance the little bleeder ports are going to snap or break off when I purge the air? Should I just give them the usual 24 hour pre- treatement with penetrating oil?

Any thoughts or comments welcome.

Tnx...





http://www.automotiveforums.com/vbulletin/showthread.php?t=1061964

Bleeders are brass IIRC on my 97.

I bought a quart of the Prestone super flush? I think I drained the system, filled with water and flush, ran a week with the flush (I only drive about 5 miles in town M-F), drained the nasty stuff out, filled with water again, ran a few more days, drained nasty stuff, filled water again, was pretty clear, drained, refilled with 50/50, and have driven it ever since, great heat now, runs very moderate temps (right around 195 and gets to temp much faster now), I also did replace the Tstat with a Stant Super Stat because it was doing the Temp thing that yours is doing........

You have an external leak....in that area, it could be the thermostat housing, the ECT sensor(that's the sensor in your picture), the aforementioned hoses, or the lower intake gaskets.....the Coolant pipe that might leak(usually the aluminum housing that the pipe goes into, it breaks at the threads) would not pool coolant in the area of the picture....

Right now you are guessing....in fact, you want us to say anything that is not too involved.....For me, I don't know how you find a leak with a dirty engine like that......clean the top of it, wash it down, and blow out the dirt and water......the with a clean engine, you can easily isolate the leak, by checking it daily.......if you have a black light, could even add dye to the coolant system to help find the leak....

Look directly under the throttle body....when it pools there, it's usually the lower intake gaskets....usually comes out near the corner bolts in the lower intake manifold......the main thing, is to find the source of the leak, BEFORE you replace parts needlessly.....

Tech (and the rest), Thanks for taking the time to reply. In all honesty, I have never had good results in cleaning an engine. No matter how much time I take to cover things up and how careful I am with washing. Invariably, something either goes wrong right away, or worse, 200 miles down the road in the middle of nowhere.

I don't mind "throwing" parts at it as long as they are not TOO expensive or the job is not TOO involved.

I have a cooling system pressure checker (Stant). It's about 35 years old. It is a stainless hand pump that tests the radiator cap and also fits on the filler neck to pressurize the system. I will give that a shot soon and see how much of a leakdown I get. I would HOPE it's not the LIM again. As I mentioned, I had it replaced 75k ago. Oil is perfectly clean (oil, no milky mush or foam. Coolant is bright green and has no particulate in it). I have not checked for combustion by products in the coolant. I don't know how or have he means.

Based on the engine temp performance, I think I am at least going to go with a Tstat. If I can get some more info on flushing I may consider that too.

I looked in the 2000 GM U-Platform shop manual (Page 6-255) and it says to remove the air cleaner and airbox. Drain coolant to a lower level. (I"ll proabably try and use some clamps on the raditor hoses). It then says to remove the exhaust cross over pipe... Does anyone know if this is an absolutely necessary step? Seems like a BIG step (The potential for rusted, snapped bolts appears high). Are the any short cuts to this step?


Thanks again for the help.

P.../NH

I have NEVER seen a thermostat housing leak on this engine.....

But if you are determined to do it, there are three ways of doing it.....

One remove nothing....the top bolt comes on easily, it's the lower one that's the problem.....you want to do this on a cold engine,, because your hands will be on/near that cross over pipe, and you could get burned......with a small 10mm wrench, or quick wrench, AND A LOT OF PATIENCE, it can be removed....OR

You will need a throttle body gasket....remove the throttle body, and you have more room and an easier job.....OR

You loosen, not remove the exhaust studs, and this will allow you to slightly reposition the crossover pipe away from the thermostat housing.....as you know, those studs are known to break, and cause more problems.....so if you go this route, soak the life out of those studs(have to remove the heat shield first) with PB Blaster, before removal....

TechII Tnx again. I think I may have confused you. No, I don't think the TStat housing is leaking, I am waiting to do a pressure test to see if I can find something. I am considering doing the TStat because of the engine not coming up to temp normally. I think the Tstat is stuck either fully or partially open.

I have replaced mine several X by just removing the throttle body (never changed the base gasket either was just careful removing it). Take it slow and easy.

The LIM could be bad again especially if the gaskets were the old design......

Good luck.

Well, I got the Dx (Diagnosis)today. It is the LIM AGAIN !!!. It IS an external leak. The car has enough wear and tear on it that I am not going to have the the LIM done again. Too expensive. I did see something about a class action suit somewhere though.

I am just going to watch the coolant level and continue adding my 2-3 cups per month. $600 buys a lot of coolant. They also confirmed the tstat is stuck either open or partially open. They wanted 3.5-4hrs to do the tstat (flat rate). MY pressure tester didn't work so well. It leaked. But the mechanic I brought it to did. At 18 lbs he could see it coming out. They were the ones that did the LIM 75k and 6 years ago.

I'll have to see where the good weather takes me in the spring and maybe I'll work on it then.

Thanks to all for the suggestions and help.

So I am revisiting this LIM thing again. My external coolant leak is getting a bit more in volume and a bit more in frequency. I have to add a few cups every week or so. There is no internal leak that I can detect. So i COULD go on just adding coolant every week. I am considering taking to the guy that did my fuel line to have the LIM done He did a fair job at a reasonable price on the fuel line. I have heard many more good things about him from the locals.

I have a couple of questions though. If I have him do the LIM:

1. Is replacing the thermostat with a Stant Super Stat at this time a good idea? I guess I am asking, in doing the LIM, is the cross-over pipe loosened or removed to give better access to the tstat lower bolt?

2. Should I have him replace the small throttle-body coolant hoses while he is in there? Or only do it if they're leaking?

3. While it is apart, is there anything else in the "minor replacement" category that I should consider doing?

As mentioned in an earlier post, the veh has 155k on it, needs tranny work (Intermittent TCC high DTC- P0742) I am not going to invest in the trans. it works well and the issue is intermittent. I want to keep the car as long as practical. It has a salvage title (due to hailstorm damage 6 years ago) so it doesn't look great. It has lots of "ball-pein" hammer type marks all over it. . The resale is very low. I have had the car since brand new and know every nut, bolt and part that has been out into it (as well as every gallon of fuel and quart of oil).

I just want to keep it running as long as practical, but don't want to put a TON of money into it. if I can put $300-$500 into it now, and get another year or so out of it, it sure beats a car payment. Another view is, I can get a lot of coolant for $300-$500.

Tnx.

You have to pull the lower intake out to replace the gaskets....with the intake off, it takes about 30 seconds to replace the thermostat...

only time I ever replaced those hoses is if they leaked....very rare for them to leak.....the one I replaced leaked because it was nicked by previous work on the vehicle...

3.5-4.0 hours for a thermostat? That's rediculous...can be done in under an hour, by removing thethrottle body....

I agree, the thermostat is overquoted.....

The Intake manifold gaskets can be done by a novice over a weekend.... Gaskets are around $60...... Might consider trying it yourself......\

Also might leave the rad cap loose so it wont build pressure and piss out coolant as fast...... try it in your driveway and see if it will work especially with the thermostat stuck open, there will be almost no pressure in the system.....