# Oil cooler lines leaking.



## 70monte (Feb 5, 2008)

It appears that the oil cooler lines are leaking on my 98 K3500 with the 7.4L. Has anyone had to replace these and if so, how hard of a job is it? Is there anything to watch out for or any tricks to making this repair easier? Does anyone have the GM part# for these lines?

My power steering cooler lines also run down next to the oil cooler lines so it may be those instead or also. All of these lines are an oily mess and now something is dripping on the carport. It looks like motor oil but I'm not sure. If these are the problem, how hard are they to replace and anyone know the part# for them? Thanks for any help.

Wayne


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## Spitz (Feb 28, 2008)

Engine oil cooler lines? Trans cooler lines? I know the engine oil cooler lines have always been a replacement part, they leak where teh ferrules are crimped.


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## mercmn91 (Dec 15, 2005)

I replaced tranny cooler lines in a 95 tahoe with 350. Don't know the part no. but they were not too bad to do. Not that hard at all.


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## MAR4CARS (Oct 6, 2005)

Those engine cooler lines always leak. While replacing those look at the oil filter adapter thats probably leaking as well . the lines attach to the radiator with fittings make sure the new lines have the o rings on them no need to use Teflon tape as the threads do not seal only the o ring does.on the engine side the lines snap into couplers i would replace these couplers as then tend to leak as well.The filter housing is held on by 2 long bolts theres a seal/gasket kit available for the housing.I know the couplers and housing gasket kit is available aftermaket the lines i've always gotten at the dealer and never checked to see if they are available aftermarket.


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## derekbroerse (Mar 6, 2004)

My truck has a factory oil cooler from a '91 Sub on it, lines were discontinued. No aftermarket sources either. Took my old lines to a hydraulics shop and had them replace the rubber sections (they were leaking at the crimp), reusing the remainder of the tubing and fittings. No leaks, very reasonably priced. If the replacements are expensive, look into what I did.


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## Spitz (Feb 28, 2008)

Yea, you should be able to cut the ferrules off and even use hose clamps if your in a pinch.. Ps- some tranny lines dont come fabricated, most times we end up making ours out of bulk brake line.


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## Clint S (Feb 12, 2008)

You want to know what my dealer said after my oil cooler lines leaked at 2 years and 18k..... " A little seepage is normal". So I said If you can show me 1 new truck on the lot that has "a little seepage" after we drive it I would be satisfied and not get the repair. They replaced the lines. Guess what they leaked again less than 1 yr later they replaced and now my 3rd set leaked too. I just live with it it is not that much.


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## 70monte (Feb 5, 2008)

The oil cooler lines on my 98 K1500 leaked when it was still under warrenty and the dealer replaced them. The ones on the K3500 look like they are leaking pretty bad. There doesn't appear to be any oil leaking from the adapter where the oil filter screws onto but I will have to look closer to be sure.

Wayne


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## dirtmandan2 (Nov 2, 2007)

I replaced the lower oil cooler line on my chevy today. Got the parts from carquest. the line was about $28 and the new quick disconnect around $8 . The job wasnt terrible, took a couple hours, I removed the oil filter and was just able to get the 1" wrench on it.


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## B&B (Nov 4, 2006)

70monte;680499 said:


> It appears that the oil cooler lines are leaking on my 98 K3500 with the 7.4L. Has anyone had to replace these and if so, how hard of a job is it? Is there anything to watch out for or any tricks to making this repair easier? Does anyone have the GM part# for these lines?
> Wayne


 Stay away from the GM cooler lines Wayne. They're still scrap and have been for a long time. Dorman makes good quality aftermarket replacements for your specific truck. Run you around $70 or so for the pair.

Their a little tougher to swap out on the 7.4's but with a little finesse they'll come out. Be gentle with the fittings and O-rings and be positively sure that the retainer clips are fully engaged...otherwise its relatively straight forward.


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## Spitz (Feb 28, 2008)

On the s10 blazers you have to lift the engine slightly for them to clear on some, not much, just have to stretch the engine mount a tad.


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## 70monte (Feb 5, 2008)

Thanks for the input. I will go with the Dorman replacements. I'm going to try to wait for a warmer day to tackle this job in case the repair goes longer than anticipated as is usually the case. I assume the new lines come with the new O-rings and clips?

Wayne


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## B&B (Nov 4, 2006)

70monte;683229 said:


> Thanks for the input. I will go with the Dorman replacements. I assume the new lines come with the new O-rings and clips?
> 
> Wayne


Sure do. At least their supposed to. Have gotten a couple that were missing the retainer clips so be sure to open the box and check before you start.


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## 70monte (Feb 5, 2008)

Ok thanks. I picked up the cooler lines today. I went with the Dorman replacements. $60 for both from Carquest. They came in a long plastic bag and the retainers and O rings are there. 

A couple of people have mentioned replacing couplers and quick disconnects during this repair job. Where exactly are these and are they necessary to replace? If the oil filter housing gasket is not leaking, should I just leave it alone or should I also replace it? Thanks again.

Wayne


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## Clint S (Feb 12, 2008)

http://www.s10forum.com/forum/f107/repair-your-leaking-oil-cooler-lines-343472/

Here is a way to repair you lines it is on an S 10 but they are similar I think. I do not know if I would do it except if I was in a pinch though.
Edit This is for the remote filter lines not the cooler lines.
I would replace the coupler a disconnects too. Just had it done on the HD, but for the tranny lines. Was the best $100 I spent having a shop do it though.


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## B&B (Nov 4, 2006)

The quick coupler disconnects are how the lines are attached at each end. Your new lines came with new clips and O-rings which will basically re-new the coupler connections. No need to replace the coupler fittings themselves as they aren't normally an issue on the engine cooler plumbing like they can be on the auto trans cooler plumbing.

Installing a fresh gasket and O-ring under the oil filter sandwich adapter is a good idea though.


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## 70monte (Feb 5, 2008)

Clint S;687178 said:


> http://www.s10forum.com/forum/f107/repair-your-leaking-oil-cooler-lines-343472/
> 
> Here is a way to repair you lines it is on an S 10 but they are similar I think. I do not know if I would do it except if I was in a pinch though.
> Edit This is for the remote filter lines not the cooler lines.
> I would replace the coupler a disconnects too. Just had it done on the HD, but for the tranny lines. Was the best $100 I spent having a shop do it though.


Years ago I had a 93 S-10 4x4 with the 4.3L and the remote oil filter that developed leaks on the remote filter lines. I bought new lines to replace them but when I went to remove them, I couldn't get them off because there was too much stuff in the way. I never replaced them and soon after traded the truck off.

Wayne


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## 70monte (Feb 5, 2008)

B&B;687209 said:


> The quick coupler disconnects are how the lines are attached at each end. Your new lines came with new clips and O-rings which will basically re-new the coupler connections. No need to replace the coupler fittings themselves as they aren't normally an issue on the engine cooler plumbing like they can be on the auto trans cooler plumbing.
> 
> Installing a fresh gasket and O-ring under the oil filter sandwich adapter is a good idea though.


I just got done looking at the new lines. The ends that go into the oil filter adapter do not have O-rings but has a metal collar on the line. The ends that go into the radiator have O-rings and the threaded fitting. Are you saying that on the radiator side, where the line screws into the radiator, that this is a quick coupler disconnect?

Since there are not any O-rings on the oil filter adapter end, what keeps this end of the line from leaking? The metal collar that is on the line at this end doesn't look like it has any rubber in it or anything to create a seal.

Since its been so cold out and I don't have anywhere warm to work on the truck, I haven't looked at the area where the lines hook into the filter adapter. I just want to make sure I have everything before I start this job. I will replace the gasket and O-ring under the oil filter adapter just to be safe. Thanks again.

Wayne


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## B&B (Nov 4, 2006)

The fittings at the oil filter adapter end have Viton seals made internal so there's won't be a seal on that end of the line. The radiator ends are O-ring like you described. 

If you desire to replace the filter adapter end fittings (just as preventative measure, although I only do if they previously leaked) make sure you use ONLY genuine GM fittings as the aftermarket fittings are garbage. IIRC the GM p/n for the fitting is 15043741 but be sure to double check as there's two different fittings used in that location throughout the years.


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## 70monte (Feb 5, 2008)

B&B, thanks for the info. When it warms up I will check to see if there is anything leaking at the filter adapter end.

Wayne


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## 70monte (Feb 5, 2008)

Well, it warmed up today and I was going to replace the lines but its way too windy and I don't have an enclosed area to work in. I changed the oil one time on a day like today and ended up with oil slung everywhere. I'm also trying to figure out how to get to everything. With the front diff in the way, it looks like its almost impossible to reach the area where the lines are clipped into a bracket. Where the lines attach onto the engine, there is hardly any room to reach up into that area to remove the clips. There is also not much room where the lines go into the radiator. This does not look like a fun job at all. This looks like one of those jobs that will take me twice the time to do and have me pissed off the whole time. Hopefully a better day will come soon.

I also discovered that my front seal on the engine is leaking again. It quit for awhile. The joys of an older vehicle.

Wayne


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## 70monte (Feb 5, 2008)

This might be a stupid question but where are the little clips that lock the lines on at the engine side? After getting under the truck again and looking at it, I cant see the clips at all. Do I have to somehow pull down the round looking piece that is at the end of the line to see them? If so, what is the best way to do this? I tried pulling on them with my hand and they didn't budge. Thanks.

Wayne


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## B&B (Nov 4, 2006)

The plastic circular things your seeing are the safety retainers/debris caps for the locking clips. You simply pry/slide them back on the lines which will reveal access for the clips on the ends of the quick connect fitting. 


To change the lines on the 7.4's you have to remove the front drive shaft, fan shroud, and driver side motor mount bolt....and then raise the engine up on the driver side. 

Sounds worse than it is. :waving:


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## 70monte (Feb 5, 2008)

B&B;694218 said:


> The plastic circular things your seeing are the safety retainers/debris caps for the locking clips. You simply pry/slide them back on the lines which will reveal access for the clips on the ends of the quick connect fitting.
> 
> To change the lines on the 7.4's you have to remove the front drive shaft, fan shroud, and driver side motor mount bolt....and then raise the engine up on the driver side.
> 
> Sounds worse than it is. :waving:


Wow, I didn't realize that it involved all of that. I guess I will have to plan this repair a little better and give myself more time. Thanks again for the info.

Wayne


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## 70monte (Feb 5, 2008)

Well, I finally got this repair done today. It took me about four hours, longer than it probably should have. I didn't have to remove the front drive shaft or the motor mount or jack the motor up. There was enough room to do it without doing that stuff. It was probably the messiest job I have done since there was oil and front diff lube all over everything from the leaking lines and previous overflowing vent tube. Thanks for all the help.

Wayne


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## Mark13 (Dec 3, 2006)

I used Dorman lines on my truck last time, I made it about 2 months before they started leaking. I've got Gm lines now that I havn't put on but I'm sure they will leak also and now that I sit here and think about it, I'm pretty sure I told him transmission lines when I wanted oil lines. :angry: I've had them for 2 months or so and I'm sure they won't take all the parts back which is around $100. I kinda think they are going to leak no matter what, it's a stupid design.


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## 70monte (Feb 5, 2008)

I installed the Dorman lines also. I was told that these were better than the GM ones. I guess time will tell. It is a crappy design. The lines on my 98 K1500 were replaced under warrenty years ago and so far they don't seem to be leaking. They do seep a little though.


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## Sydenstricker Landscaping (Dec 17, 2006)

I did I guess a hillbilly fix on my 94 2500 350. I took the fittings and everything out of the oil lines. Put barbed fittings with some sealer tape on the radiator and by the filter. Then put high pressure rubber fuel line in its place. Never had a single seep, leak or drop there afterwards. Ran them through all the stock locations too, and put some of that plastic wire crap around any areas that I thought could wear thru. The best part about the rubber lines....they will never rust. Drove it like that for 30,000 miles and not one single issue. Sold it and still like that to this day.


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## 70monte (Feb 5, 2008)

Sounds like a better solution than the factory lines. If these end up leaking, I will probably try doing something similar. I also replaced the valve cover gaskets the next day. That job didn't take as long and was a lot less messy.

Wayne


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## Sydenstricker Landscaping (Dec 17, 2006)

It worked good for me. Sold the truck 3 years ago almost to the day and talked to the guy a few months back, and not a single leak. Still got the same lines there too. I got rid of it at 200K, has over 300K on it now. I guess the hillbilly fix worked, lol. Wish I would have kept that one though. Still has the stock engine& trans- never been touched either. And I plowed with it too


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## 70monte (Feb 5, 2008)

Well, I finally drove the truck today for the first time since the repair and I still have something leaking. It must be power steering fluid but I'm not sure since its running down in the same area as before and the fluid looks kind of dirty. It does look like a little oil is seeping out of the bottom oil cooler line where it screws into the radiator. I probably should have wrapped teflon tape around the threads but I couldn't get down there very well. I hope the o-ring didn't split since its also seeping around the metal line.

I also changed over to 10W-30 on this oil change and the truck doesn't feel as powerful as before. Maybe after some miles on the oil it will feel better.

I don't know what is involved is changing out the power steering cooler lines but it doesn't look fun. Has anyone done this before? They may just have to leak.

Wayne


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## B&B (Nov 4, 2006)

The PS lines aren't too terribly tough if you pull the fan shroud and the front skid plate. Doing so gives you enough room to snake your way through the repair. And also allow you the room to get into the cooler line you just replaced.

It'd also be a good time to clean up the oil mess while you have the access in there. Certainly would make it easier to not only work but to keep an eye on any future leaks as well.


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## 70monte (Feb 5, 2008)

B&B, thanks for the info. Is the power steering cooler and lines all one assembly? Is this a dealer only item or is there an aftermarket replacement that works well? Thanks.

Wayne


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## B&B (Nov 4, 2006)

If the steel sections of the return line are still in good condition (not rusty) then all you need to do is change the rubber sections of the hose using high pressure trans cooler hose and good stainless hose clamps. Your return (which is where the cooler is) is all low pressure anyway so clamps are more than acceptable for the job, but I use the high pressure hose as well as it will outlast anything else you may consider using....like rubber fuel hose for example.

If you also looking to replace the high pressure hose assembly between the box and the pump (which I'd assume you are), it can be purchased at any parts store, it's not a dealer item. So no trip to the dealer will be necessary with this repair.


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## 70monte (Feb 5, 2008)

B&B, thanks for the info. I will look into doing that since the cooler itself looks to be in good shape and I think the steel sections of the hoses appear to be fine also. Everything is coated in fluid so its hard to tell. 

Wayne


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