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Old 12-23-2012, 03:04 PM
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Coolant leak diagnosis

I'm having lots of fun today trying to diagnose a coolant leak. ('98 F355B).

Here are the symptoms: small puddle of coolant under the front of the engine, along the centerline of the car. Just looking underneath I could see a drip forming on the undertray that's just forward of the engine. The puddle becomes about a square foot in size after a few days, so it's a slow leak. It seemed to start after the weather got cold. The car is garaged, but the garage isn't heated.

From underneath the car it's clear that coolant is leaking down the front of the engine (pics 1 and 2). It's hard to follow the trail up much higher than I've circled in Pic 1. It also looks like the coolant might be leaking down the rear of the fuel tank, and that might be how it ends up dripping from the under tray (?).

I took off the expansion tank, and I couldn't see any obvious leaks. Because it's possibly leaking on the other side of the firewall, I suspected one of the two hoses circled in Pic 5. Pics 3 and 4 show what I think are the clamps for those hoses. I tried to tighten them (they're pretty hard to get to), but they weren't loose, and I doubt that I've solved the problem (it was obviously still slowly leaking - I could see drips forming as shown in pics 1 and 2).

Any ideas on what else I should check? This seems pretty difficult without removing the fuel tank or something. Tips on how to get better access? Any help much appreciated.
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  #2  
Old 12-23-2012, 03:26 PM
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Almost certainly it's coming from the weep hole in the water pump. Are you due for an "engine-out" service?
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Old 12-23-2012, 03:35 PM
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Mine was leaking in the same way as yours when I got it last January. I'm not much help to you however as I performed the engine out service at that time and rebuilt the water pump never did determine where the leak was coming from and haven't had a problem since.
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Old 12-23-2012, 03:37 PM
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If you are lucky, one of those two hoses might have a small crack or leak in them...happened to me once. Otherwise, might be the water pump as Tim mentioned.
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Old 12-23-2012, 04:19 PM
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Thanks for all the quick responses!

Major was done earlier this year by previous owner. Receipts show that he used the Ricambi 30K kit, and I don't see a separate line item for the water pump. If I'm reading the Ricambi site correctly then it doesn't include the pump.

Sounds like I need to google this issue. Thanks.
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Old 12-23-2012, 04:36 PM
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water pump

Quote:
Originally Posted by LAracer View Post
Thanks for all the quick responses!

Major was done earlier this year by previous owner. Receipts show that he used the Ricambi 30K kit, and I don't see a separate line item for the water pump. If I'm reading the Ricambi site correctly then it doesn't include the pump.

Sounds like I need to google this issue. Thanks.
Ricambi does not include the water pump bearing/seals in the 30 k kit..... no retailer does.
When I did my last major I changed the water pump seals & bearings to be proactive.
The water pump can be pulled on a 355 with out removing the motor.....but you have to remove the entire water pump support assembly which involves the heat exhanger seals also needing to be removed/replaced.
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Old 12-23-2012, 04:40 PM
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diagnosis of coolant leak

but before you go there......you should have the cooling system pressure tested to identify the actual source of the leak.
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Old 12-23-2012, 05:03 PM
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I have just confirmed that it's definitely dripping down the rear of the fuel tank (in addition to the front of the engine). Does that narrow down the source? I suppose it's possible I have two leaks! I'm hoping that if it's not two leaks then it eliminates the water pump as the problem?

I've been reading about similar slow-leak problems. It seems that pressure testing is sometimes not useful since the pressure can seal the leak. I suspect that may be the case for me. I may try some kind of dye kit though.

Is there a logical order of things to remove to get better access? I have a bad habit of removing too much and making a complete mess.
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Old 12-23-2012, 05:50 PM
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Your best bet is clean all the old dirt and fluid off then doing a pressure test and use some UV dye in the antifreeze. Use a UV light where you suspect it leaks. This way you see exactly where it comes from fresh.

Or any combination of the above to suit your needs


Good Luck
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Old 12-23-2012, 06:30 PM
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Put the car on a lift, remove the rear underpanel and carefully get under it while it's running (I do it all the time). It is possible (with a bright light) to see the water pump weep hole from below. If it's leaking there (or other places) you'll have a good chance to see it. Pressure testing while observing from below may also identify the leak. I have seen some water pumps that only leak when running. Try it both ways.

It is possible to replace the pump "in the car", but it is very difficult to do it that way and I do not recommend trying. In addition, the replacement seal (you won't be buying a new complete pump) requires special tooling to remove/install. Without it, the pump will leak, but you won't know it until it's all back together. Ignore this at your peril.
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Last edited by 2NA; 12-23-2012 at 06:36 PM.
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Old 12-23-2012, 07:12 PM
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sometimes the leak is from the valley hose to clamps and runs down to fool you into thinking it is the WP. Pressurize the system and the leak will become obvious.
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Old 12-23-2012, 08:25 PM
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I really appreciate all the great tips.

I might not be completely on the same page...I am kinda new so I probably seem slightly not smart. Everyone seems to agree that I should pressurize the system to see the leak, but I can see it leaking (dripping) without pressurizing. The problem for me is getting line of sight to the offending location. I'm thinking that points toward removing some more stuff around the expansion tank area, using a mirror, and maybe getting a dye kit.

I'm sure someone will let me know if I'm way off.

At least I have a week off work to play.
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Old 12-23-2012, 08:33 PM
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Quote:
Originally Posted by LAracer View Post
I really appreciate all the great tips.

I might not be completely on the same page...I am kinda new so I probably seem slightly not smart. Everyone seems to agree that I should pressurize the system to see the leak, but I can see it leaking (dripping) without pressurizing. The problem for me is getting line of sight to the offending location. I'm thinking that points toward removing some more stuff around the expansion tank area, using a mirror, and maybe getting a dye kit.

I'm sure someone will let me know if I'm way off.

At least I have a week off work to play.
You weren't paying attention.

It is very unlikely that you'll see anything meaningful from above.

Probably the only part that you'll need to remove is one underpanel. You will need to raise the car (preferably on a hoist), and look from underneath. A bright light and an inspection mirror would be very helpful.

If it is leaking, you should be able to see where it is coming from.
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Old 12-23-2012, 08:50 PM
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For what it's worth when I had a leak issue at the front of the engine (mine was oil) and couldn't see with those close tolerences up there, I ended up with a cheap tiny video camera like you use for web casting, taped it to a piece of coat hanger and looked around with that hooked to my computer.
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Old 12-23-2012, 09:17 PM
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My water pump leaked after a major. Tom jones at SportAuto replaced it without removing the engine. It may be tricky but it certainly can be done.
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Old 12-23-2012, 09:21 PM
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Quote:
Originally Posted by 2NA View Post
You weren't paying attention.

It is very unlikely that you'll see anything meaningful from above.

Probably the only part that you'll need to remove is one underpanel. You will need to raise the car (preferably on a hoist), and look from underneath. A bright light and an inspection mirror would be very helpful.

If it is leaking, you should be able to see where it is coming from.
Sorry, I thought it was clear from the pics that I was under the car with the undertray ahead of the engine off. From down there I could see the hoses that I originally mentioned. One looks like it might have been leaking, but it's hard to tell. I was dry but maybe crusty. And if I need to replace it and the clamp, then I could probably use some advice on how to access it. It seems to me that I'd at least need to remove the fuel tank, but like I said I'm new and clueless. I doubt I should try any serious surgery until I'm 100% positive of the source.

I like the camera on a coat-hanger idea!

Thanks.
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Old 12-24-2012, 10:56 AM
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all those hoses can be replaced with the engine in the car, from the top. Remove:

Coolant tank
Power Steering resevoir
And engine lid if you are so inclined.
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Old 12-24-2012, 12:30 PM
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Quote:
Originally Posted by yelcab View Post
all those hoses can be replaced with the engine in the car, from the top. Remove:

Coolant tank
Power Steering resevoir
And engine lid if you are so inclined.
Thanks! Yes, the engine lid will have to come off. I'm short, and I end up pretty much swimming in the engine.

My plan is to get dye (local store doesn't carry it so I'll need to make a trip to the next town), take stuff off to make room, then see what I can see. Might not get to it today.
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Old 12-29-2012, 01:58 PM
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Success...I hope.

Taking the engine lid off was a must. Much more comfortable swimming above the engine that way. I loosened the expansion tank, but left the ps pump in place.

I used UV dye. For some reason the leak slowed down quite a bit (maybe because I had a heater on in the garage?), and it took a day to show up properly.

From underneath the trail was quite obvious, and while I could see coolant around the water pump, I could not see any dripping from the weep hole (thank goodness!). I couldn't find the source of the leak from underneath though, even using a mirror.

The two hoses I originally suspected were cleared of all charges. Definitely not those. They were clean, looking from both the top and bottom.

Because I saw coolant around the water pump I figured something was probably leaking on top of the engine. From above, poking around under the expansion tank, I eventually saw a big UV glow where the "union" (circled in pic) screws into the water pump. With a regular light I could see coolant oozing in that location. I very much hope that the leak is actually from the hose clamp just above (clamp not shown in pic, but it's where the rubber hose meets the union). There was coolant around the clamp. I have tightened the clamp, not too much so I don't strip it, and hopefully (have I used that word enough yet?) all will be dry.

...then I can start working on locating the oil leak I just found.
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  #20  
Old 12-30-2012, 12:49 PM
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There was still a small leak this morning. I found a pretty obvious source at the rear heat exchanger coupling. I guess I missed it because it's pretty far from the front of the engine where the coolant finally makes it to the ground. I think this one is it. The clamps were pretty loose, and I tightened them pretty convincingly.

I won't put it all back together quite yet though.
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