Mystery coolant loss 4.6

[OldCadTech]

I'm going to guess this has been asked before but I couldn't find it in the forums, but it's day one at CaddyInfo

I recently acquired a 1999 DeVille 4.6, the previous owner stated the engine over-heated but it was immediately shut-down and towed to a repair facility, not a dealership. He stated the "shop didn't do anything but look for obvious leaks". They told him that they knew the NorthStar "reputation" for head gasket failure and they didn't want to do the job because it was a loss due to flat rate at 20hrs and they couldn't do it and make money. I'm thinking no one checks coolant levels especially with a black recovery jar so it was probably low on coolant for a while. Then the story begins....

Checked the engine oil for "milkshake" Idled the car for 20-25 mins, watching the coolant temp, checked for mis-fire DTC's, and watched for bubbles in the recovery jar, cooling fans were operating as designed. Everything was operating normally so I filled 3 gallon jugs with water for the 25 mile trip home, topped off the coolant recovery jar/surge tank, put the "radiator" cap on and headed for home. Only one short moderate climb and the temp rose to 210 about halfway up and stayed there until the road leveled out on the other-side, then the temp dropped to 199 and only rose to 205 when idling at a stop sign then dropped again to 199 . Highest speed was 65mph but only for 5 miles or less. I parked it and the next morning checked the coolant level and I had to add nearly 3/4 gal, no coolant puddles under vehicle so I'm thinking it had a little air.

I have approximately 100 "normal" operating miles on it now.

I've checked all the usual spots for a NorthStar to leak, T-stat housing, water pump, heater hoses, T-body, radiator tanks and nothing is out of the "norm". No vapor from the exhaust, but I have detected a faint coolant smell a couple of times from near the drivers "A" pillar but I lost it when I opened the hood. Without access to a rack I'm not eager to try an engine pull on stands. What have I missed??? Maybe bars leak? (OMG - don't believe I said that) Next step - I'm going to pressure wash the engine compartment and park it over some wee-wee pads. Hoping someone had the answer

[KHE]

If you smell coolant, then you have an external leak. Borrow a radiator pressure tester from Autozone (in their loan a tool program) and you can pressurize the system to 15psi when cold, then go over the entire cooling system looking for leaks. Check the water pump crossover housing gaskets - the crossover housing is on the driver's side of the engine compartment and connects to both heads. There are four gaskets.

The other leak point could be the heater core pipes that run along the back of the engine. Have you checked the purge line to make sure it is flowing? The purge line is the 1/2" hose that connects near the top of the surge tank from the throttle body area. Remove the pressure cap, disconnect the purge line and point it into the neck of the surge tank. Have someone start the engine - there should be a steady stream of coolant from the purge line. If not, trace it back to the water pump crossover and remove the hose at the nipple. Then remove the nipple and clean it.

You might also want to test the coolant for combustion gasses although your temperatures seem normal to me.

[Cadillac Jim]

If everything KHE mentions checks out, it is probably a cracked radiator tank over where you can't see it. Look for that as best you can during the pressure test.

[OldCadTech]

Sorry, I didn't mention I have a pressure tester and did pressure test @ 15psi. I thought the system was 18psi but it had a 15lb cap on it, looked original and I don't have SM's anymore so I went with that. I did see circulation in the recovery jar so I "assumed" the line was clear but that is a good test to do anyway.

Thanks for mentioning the htr hose pipe at the back head! I now recall the other owner saying he had the blower motor replaced (it still looks new, so it was recent) and I know the pipe gets "repositioned" in the process... maybe

The left tank looks dry, both trans cooler lines are clean and dry, but as you know the front of the tank is invisible and the core support is packed with leaves and is oily. The right tank has power steering fluid on it from a leaky reservoir, pump or pressure hose, so it's really hard to tell but I don't think there is any coolant there. Neither tank is bulged at all.

Thank you for the replies, I'll let ya know...

John

[rockfangd]

Welcome To Caddyinfo.

check your side tanks on your radiator for swelling and cracking, especially on the passenger side.

check the coolant crossover pipes on the firewall side of the engine.

I assume you see no puddles on the ground.

Best way to see if you have HG failure is to find a long hill and step on it. You can watch the temp climb and if it is bad it will go up rather quickly.

Check the waterpump weep hole. It should leak onto the trans if it is leaking.

Keep us posted

[BodybyFisher]

If you see any white deposits on the radiator tanks where they meet the core its evidence of a leak. Check that the cap does in fact hold 15 PSI. Check the coolant concentration to make sure its at least 50% coolant. Stick your nose in the coolant tank and see if you have an exhaust smell.

I just replaced a couple of hoses, a water pump and water pump housing seal and still smelled coolant on my friends 98 Seville. With a flashlight I could see the radiator leaking where the core ribs meet the flat flange that the tanks are attached to. Cooling systems can be funny, everytime you fix one spot, the pressure finds the next place to leak.

Check to make sure your water pump belt is good and that the water pump belt tensioner is providing tension and not bound up.

You wont see chocolate milk in the coolant tank as oil and water do not normally mix often unless the head is coming off, that is not an indication we look for.

[OldCadTech]

Thanks a lot, that's why I posted on Caddyinfo - peeps that have been there and done it too...

Work took front place this morning so I haven't had a chance to get back under the hood, but still put more miles on it trouble free.

Rockfangd - You are correct there are no puddles or trails to follow. It has been raining here so I haven't had a completely dry under-carriage to look at either I have to drive about an hour to get to a big enough hill to do a test, might be a Sunday test drive tho.

BodybyFisher - good advise too, I've never had good luck with the cooling system exhaust testers, but haven't thought about sticking my nose in the tank either... I've resealed a LOT of case halves but I've never had the heads off of a NorthStar, I was going on instinct when I pulled the dipstick. I did the 4.1 - 4.5 - 4.9 milkshake confirmation a lot.

BTW were you really bored when you came up with the idea of an LT1 twin turbo engine swap?

[BodybyFisher]

OLd Cad Tech, when the head gasket blew on my 96, there was a STRONG exhaust smell in the coolant tank.

Good that you pressure tested the system. As you know some leaks only show up under pressure and then the coolant vaporizes when it hits the atmosphere. You smell it but you don't see it.

Let us know how we can help

Ha Ha, that isn't my Fleetwood, I belong to about 20 Facebook Cadillac sites and someone owns that, I thought our Fleetwood owners would love it

[rockfangd]

That fleetwood body style is beautiful. Kudos to the engineers that designed that body. I would love if cadillac kept with that body style for a few more years before making drastic changes.

You know you are in a cadillac when you drive one of those

[OldCadTech]

I have to agree, the fleetwood was a great ride, made ya feel "secure"

Tomorrow if the weather holds off the rain I'll get back on the Deville. I did get a brief look under the car late this afternoon and the pavement was dry, no puddles no coolant hanging. I'm still planning on pressure washing after i check the heater pipes along the back head...

Can either of you tell me about a head bolt hole repair that is similar to heli-coil but better???? Sorry, can't think of the name of it and some-timers won't let me remember where I seen it. Seems to me I read that head bolt stretch is still a problem even though I also thought the NorthStar was immune... As many of the NorthStars as I have worked on, I still have never had the heads off one. I have had heads off all the other Cadillac engines tho.

John

[Logan]

The head bolt thread tool is by Time-Sert.

The 1999 version Northstar uses kit J-42385-500. It is available as a rental.

[BodybyFisher]

See this site for more, information

www.timesert.com

This is the GM sanctioned method to repair the block head bolt thread after a head bolt is removed. All 20 bolt holes in the block must be repaired.

Hopefully you wont need to go there.

[Logan]

It should be noted....there are both Time-Sert and GM dealership Kent Moore versions of the tools.

The Kent Moore versions are really using Time-Sert tooling. But they are packaged a different way. Some Kent Moore kits require tools from other Kent Moore kits to complete repairs.

With Kent Moore....the assumption is you are a GM dealer...so you already have the other kit sitting nearby.

[BodybyFisher]

Thats great info Logan, you told that to me last year, and I forgot the details, so its great to see in print.

I just bought the timesert J-42385-500 kit cant wait to use it.

[Logan]

When I talked to you....I didn't have the 500 kit available for rental. I now have a 500 kit available to rent.

[Cadillac Jim]

The radiator cap is a 15 or 16 psi rating. A leaking radiator cap will cause boil-off of the coolant. If there is any doubt whatsoever, I would get a new AC/Delco 12R7 or 12R7S (the S version having a pressure release lever), clean the sealing surface, and be sure.

[OldCadTech]

Logan - that is sooo cool. I watched the videos a lot better, cleaner install than heli-coil ... Thanks for the info.

Update - I stuck my nose in the coolant tank, NO exhaust odor at all, also no bad coolant smell either, coolant needs flushed and replaced but it's not barn paint. Heater pipes at rear head look good, no pry-bar marks anywhere. Put another 50 miles on the vehicle with a lot of ignition cycles ( 8-10 ) still smelling coolant near the "A" pillar when getting out. I did notice there is about 2" of critter chewed out hood seal missing at the cowl near the dr w/shield wiper pivot so an easy out for any "aromas"....

[OldCadTech]

Jim - Thanks, actually I did put a new cap on. i wish I had a D/ship closer, I'm a firm believer in GM parts but it is 60miles round trip to GM parts, I've been using a local parts store, I don't like the quality of some of their parts but they make it right if anything happens.

[KHE]

Have you checked the inlet tank on the radiator? It is the left tank and it sees all the stress of the hot coolant. Is the water pump dripping from out of the weep hole underneath? The next thing would be to check the water crossover housing to head/block gaskets.

If it is the water crossover gaskets, that job is such a PITA with the engine in the car that it would be tempting to add the GM/Bars Leaks tabs in the lower radiator hose and drive it.

[KHE]

Logan - that is sooo cool. I watched the videos a lot better, cleaner install than heli-coil ... Thanks for the info.

Update - I stuck my nose in the coolant tank, NO exhaust odor at all, also no bad coolant smell either, coolant needs flushed and replaced but it's not barn paint. Heater pipes at rear head look good, no pry-bar marks anywhere. Put another 50 miles on the vehicle with a lot of ignition cycles ( 8-10 ) still smelling coolant near the "A" pillar when getting out. I did notice there is about 2" of critter chewed out hood seal missing at the cowl near the dr w/shield wiper pivot so an easy out for any "aromas"....

FYI, Heli-Coils will rip out of the block when the heads are torqued down. Time Fastener makes a Bigsert Kit to repair a block that has been damaged by Heli-Coils.

[OldCadTech]

KHE

As far as I can tell the tank looks good, the trans cooler nuts and the tank are dry, the tank to core "pinch"is also clean, but as you know the front of the tank is almost impossible to see, I don't see any trails on that side, but the weather hasn't been cooperating with me either

[BodybyFisher]

John, look closely at the water pump inboard side where the belt is. The water pump can leak 2 places there 1) the water pump seal just like all other water pumps, it will leak out of the weep hole, 2) the water pump has a body o-ring, and it can leak. When the engine is hot get a strong flashlight and look down there for steam.

The crossover is attached at 4 points and 4 seals are used, they are famous for deteriorating and they can leak under pressure. This seal has 45k miles on it and it failed.

Those timesert videos are very cool glad you saw them.

[OldCadTech]

KHE - Wow, what you said about the heli-coils made me think of all the times I must have dodged the come-back bullet. I did a lot of main cap holes, stacked em 2hi on the 4.1 & 4.5 head bolt holes etc...

BodybyFisher - Thanks for the visual of the c/over seal gives me an idea where the weak point might be..

[BodybyFisher]

Old Cad Tech, that seal above is most likely a very cheap aftermarket part from Taiwan, all 4 seals had damage, 2 because the mechanic left the 4 bottom bolts loose were very bad. The OEM part is usually good for 100K, I pulled the crossover on my 96 at 90K and while the original seals were damaged and burned and had trapped the tablet sealer material didnt look as bad as above which disintegrated.

The problem is that you never know what work has been done, the quality of the parts and whether the so called mechanic torqued the bolts back correctly. On my 96, once I replaced those seals my coolant smell stopped.

The crossover job is not easy the first time you do it, I have done it 4 times now and it gets easier as you develop a method. I bought stubby fine tooth ratchet wrenches for the job. If you ever decide to do the job we can provide tips.

[Cadillac Jim]

One problem with repairing old cars is that when your mechanic calls his parts house with the make/model/VIN, they will come back with the lowest possible price. It's up to the mechanic to ask for OEM quality or heavy-duty parts. As an example, look on RockAuto or other parts supplier of your choice on the make/model of your choice and drill down to a common part, like brake rotor/pad kits. You will see three categories, "Daily Driver" (AKA grocery-getter), "Performance" (AKA OEM), and "High Performance" (sometimes OEM for high performance cars or options). Sometimes you will see a "Heavy Duty" (AKA truck or towing, track or off-road, premium performance, etc.) category. Then, there is a check box at the top of the parts selection box "Choose for me to minimize cost" that is the default for old cars when you phone a local parts house. This makes it hard to keep from downgrading an older high-performance car unless you bring your own parts to the party. Even the dealer often will do this. Often the mechanic or dealer never thinks to ask the owner about this because most of them think of lowest-price-parts is a no-brainer for an old car. This is a HUGE argument for DIY.