3800 coolant loss

[holorinhal]

99 pontiac gp. a couple of days ago the car started to get really warm while sitting still at a drive thru. When I got home and it cooled down i checked the coolant level and it was low. I had to add about a cup and a half of coolant. Two days later and the car starts getting warm again while sitting still. I get home and check the coolant level again and it is low again and had to add about 1 cup of coolant. I have looked all over and there are no signs of any leaks. Not even a drop on the ground, so where is the coolant going? I have felt the carpet and it is dry where the heater core is. I have checked all the hoses and see no leaks.
I replaced the lim gaskets and plenum gaskets and water pump and new themostat and elbows , about a month and a half ago and evey thing has been perfec until two days ago I have also checked for water in the oil and there is no sign of that. I have a 195 tsat in and the temp runs right near there all the time while on the move. any ideas of where the coolant could be going?

[tms8582]

Are the fans turning on when warmed up and sitting still? If not maybe the motor is getting too hot and your losing coolant in steam out of the rad cap

[holorinhal]

Are the fans turning on when warmed up and sitting still? If not maybe the motor is getting too hot and your losing coolant in steam out of the rad cap

When I was checking for leaks this afternoon after it had goten warm the fans did kick on, but i cannot say if they comon while I am in the car sitting still. I have often wondered if they were working properly. Any way to test? I was thinking of replacing the relay just for the hell of it.

[Elite6]

What about head gasket? Wondering also if air in the lines could cause that symptom?

[holorinhal]

What about head gasket? Wondering also if air in the lines could cause that symptom?

I see no evidence of a head gasket, IE,no oil in water,no evidence of blow by from blowing out the dip stick and no exhaust gas in the radiator by blowing coolant out the neck with cap off, however I have nat done compession tests.
When I changed the lim and plennum gaskets, I refilled the radiator,let warm up to op temp and bled the cooling system four times, let cool and toped off. I drove it the next day and rechecked the coolant and it did not need any more top off. I had not had the cap off untill two days ago.
when i got home this afternoon ,coolant was low, I toped off with about a cup. I went for drive for some erands for about 15 miles, stop and go with stopping and starting of engine. When I got home I turned off engine. I felt radiator hoses and they were hot and hard ,as in tight with presure.
I did touch the radiator cap at one point and it was cool. Ilet engine cool and checked the fluid and it was low again,just in that short time about a cup.
I let cool toped off and with the cap off right after starting i could not see the fluid. Toped off let run with heater wide open untill getting a litle steam , put on the cap and ran to op temp . I opened the bleeder screw untill fluid came out, which was imediately. ran and bled once more. then toped off. I will check in the morning, before starting, just for curiosity sake to see if it needs topping off.

[BillBoost37]

This could be very important or ... not.

I'm going to assume by you not saying which model you have, that you have a naturally aspriated model. You say you replaced the plenum gaskets, did you put your original plenum back on the motor and not plug the coolant ports on the top of the LIM? If so, it's possible the area inside that manifold around the EGR tube area has developed a crack and is leaking slowly and internally. The heat/cold cycles cracks it over time and the coolant passage is on the other side of the EGR wall area. It's a bad design. The fixes are to put a new UIM on or plug the coolant ports on the LIM.

http://www.grandprixforums.net/how-mod-lim-46931.html

If you don't investigate this rather quickly, it could hydrolock the motor. Of course..that's if..it's the UIM.

If not..I'd think it might be a side tank on the radiator. They usually only leak when hot and under pressure. Which makes it tough to spot the leak.

[holorinhal]

This could be very important or ... not.

I'm going to assume by you not saying which model you have, that you have a naturally aspriated model. You say you replaced the plenum gaskets, did you put your original plenum back on the motor and not plug the coolant ports on the top of the LIM? If so, it's possible the area inside that manifold around the EGR tube area has developed a crack and is leaking slowly and internally. The heat/cold cycles cracks it over time and the coolant passage is on the other side of the EGR wall area. It's a bad design. The fixes are to put a new UIM on or plug the coolant ports on the LIM.

http://www.grandprixforums.net/how-mod-lim-46931.html

If you don't investigate this rather quickly, it could hydrolock the motor. Of course..that's if..it's the UIM.

If not..I'd think it might be a side tank on the radiator. They usually only leak when hot and under pressure. Which makes it tough to spot the leak.

it is a 99 GP GT, 3800 na. I did reuse the existing plenum with all new felpro gaskets. I did not plug any coolant ports.
Would pluging the coolant ports mean removing the LIM again or just replacing the plenum(UIM)?

[holorinhal]

So is there a way to test to see if the UIM is leaking internally? Is there a way to test if the side tank is leaking?
If the UIM is leaking, wouldnt I smell coolant from the exhaust and would I see moisture from the exhaust tips? I do not smell any coolant from exhaust and there is no moisture.
I do smell a faint coolant smell from up front ,but when I open the hood and stick My head under the hood I do not smell any coolant.

[copgtp]

You need to replace the coolant elbows. My guess is because the o-ring is rubber, changes in temperature may alter the spray pattern.

Easy fix, do a search here and you'll find the write up.

[FordMan77]

When you install the new elbows, make sure you lube the o-rings up just a bit before installing them so they don't roll or get crooked in the LIM. Then just keep the tensioner assembly as straight as possible during reinstall.

I actually smeared a small film of RTV around mine when I installed the motor just to make sure it sealed. So far, no issues.

[holorinhal]

When you install the new elbows, make sure you lube the o-rings up just a bit before installing them so they don't roll or get crooked in the LIM. Then just keep the tensioner assembly as straight as possible during reinstall.

I actually smeared a small film of RTV around mine when I installed the motor just to make sure it sealed. So far, no issues.

Yea I did lube them before I put them in. I was wondering if it would help to apply a little rtv sealant. How long has yours lasted with that application?

I am actually in the process of replacing them now. I have it torn down ,just waiting for it to cool down alittle.

[FordMan77]

It's been about 6 months I guess since the replacement motor went in. I had done it before I chunked the original motor when I took possesion of the car and they were still leak free and that was over 2 years.

[holorinhal]

You need to replace the coolant elbows. My guess is because the o-ring is rubber, changes in temperature may alter the spray pattern.

Easy fix, do a search here and you'll find the write up.

Thanks copgtp. I do know how to replace them. I just replaced them two months ago. I was just wondering why they would go bad again that quick? The old ones were not leaking when I changed them.