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99Sporty
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Mar 25, 2015, 11:59 PM
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Miata Coolant in Oil
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What's up all, I have a couple questions I could use your expertise on. I have a 1999 Mazda Miata sport with the 1.8, and the engine has around 100,000 miles on it, no hard driving. Recently I noticed that the coolant level was low, added some, and it became low again. I drained the oil and sure enough it was coffee colored from coolant contamination. I also flushed the radiator and noticed some oil there. The engine starts fine and runs alright, slightly rough. My mechanic did a compression and leakdown test and it checked out, no problems there. As it stands, I drained the coolant and filled the engine with fresh oil and have not ran it any more. Here are my questions:
1) Given that compression and leakdown tests were fine, is it still possible that this is a blown headgasket or could the coolant be entering the oil passageways somewhere else?
2) Given that the engine was ran with coolant in the oil, is it worth replacing the headgasket or is the whole engine shot?
Thanks for your help.
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Hammer Time
Ultimate Carjunky
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Mar 26, 2015, 2:11 AM
Post #2 of 17
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Re: Miata Coolant in Oil
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There are lots of paths for coolantto enter the oil without showing up in a compression test. You could have a cracked block, cracked head, head gasket between ol port and coolant port, etc. Make sure it doesn't have any oil coolers that could be faulty first.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
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Mar 26, 2015, 2:21 AM
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Re: Miata Coolant in Oil
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Dang! Not good, that's for sure. Coolant in oil and oil in coolant. It could pass anywhere the two are present, head gaskets, cracks and such. Does somehow this car use the radiator to cool engine oil as inside the radiator either OE or someone's idea to do that?
I'd pressure test cooling system first I think now with plugs out and hope it's just a head/head gasket problem limited to just that and no unseen damage to engine. Bearings and more than plain passing compression test could have happened.
Cooling system with oil - the rubber products, hoses and even water pump will probably go soft such that all must go WHEN solved.
More testing IMO to nail it down exactly where and what the fix will be. It's possible for a head gasket to pass a leak down test that way and not show but could pass coolant and oil back and forth at other times and pressures?
More testing needed now while it's intact and being this car probably would go for it up to an engine if it got to that,
T
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Discretesignals
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Mar 26, 2015, 9:50 AM
Post #4 of 17
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Re: Miata Coolant in Oil
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Coolant and engine bearings don't mix. Once coolant mixes with oil, it will damage the bearings as the engine is running. Kind of a gamble when dealing with one of those. That is unless you figure out the problem, make the repair, inspect the engine bearings and surfaces for damage, and flush out the block and oil ports.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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99Sporty
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Mar 26, 2015, 2:31 PM
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Re: Miata Coolant in Oil
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Thanks for the advice guys. I know the coolant could have caused some permanent damage but as this is not my primary transportation I'd like to do a budget fix if possible rather than having to swap in a new engine. Also thanks to Hammer Time, I didn't think it had an oil cooler but I double checked and it does, I'll look into that next before I tear the whole thing apart.
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Tom Greenleaf
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Mar 26, 2015, 2:41 PM
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Re: Miata Coolant in Oil
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Just RE oil cooler: Doubt it and really only worried if one was inside a radiator end tank. Auto transmissions it's common, not so much for engine oil,
T
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99Sporty
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Mar 26, 2015, 3:12 PM
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Re: Miata Coolant in Oil
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Just out of curiosity why don't you think it could be the oil cooler? The oil cooler on a Miata mounts underneath the screw-on oil filter right on the block, it seems like if this broke it could dump coolant strait into the oil system and cause the problems I'm looking at
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Discretesignals
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Mar 26, 2015, 3:28 PM
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Re: Miata Coolant in Oil
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One way you could probably test the cooler is to unbolt it from the filter mount. Leave the hoses attached and then pressurize the coolant system with your pressure tester. You'll be able to tell if the cooler is leaking.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Mar 26, 2015, 3:29 PM)
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99Sporty
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Mar 26, 2015, 4:00 PM
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Re: Miata Coolant in Oil
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Thanks that's what I'll probably do, I'll have to see if I can get in there with a long socket and get that nut out. Its in a tricky spot underneath the intake manifold, nice picture
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Tom Greenleaf
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Mar 26, 2015, 6:25 PM
Post #10 of 17
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Re: Miata Coolant in Oil
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ANYWHERE the two pass is possible especially under pressure with either. Test could include pressure up cooling system and look. Once you open up anything that prevents you from pressuring up cooling system that is lost for a test. Hate to see you dig all into this and NOT know where it came from,
T
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99Sporty
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Mar 27, 2015, 5:59 PM
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Re: Miata Coolant in Oil
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Oil cooler was really hard to get to so I disconnected the lines, found some black oily sludge in them. Filled the radiator with distilled water and ran a hose from the throttle body to the block to bypass the oil cooler. Ran the engine for a bit and was still seeing oil coming into the overflow tank so I don't think the cooler is the problem. Did another compression test today and was getting between 170 and 180 psi for all 4 cylinders, looks like a healthy engine unfortunately. I think it is probably a problem with the head gasket just not at the cylinders but I sure wish I could be more confident before I tear the thing apart. Question for you Tom, what could I find by pressurizing the cooling system? I know that oil is getting in somewhere and coolant is leaving somewhere so it shouldn't hold too much pressure, would I just be looking for coolant leaking somewhere?
(This post was edited by 99Sporty on Mar 27, 2015, 6:03 PM)
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Discretesignals
Ultimate Carjunky
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Mar 27, 2015, 6:15 PM
Post #12 of 17
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Re: Miata Coolant in Oil
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You may be right that there something internal going on such as a head gasket leak between a coolant port and oil drain back hole or maybe a cracked head which you wouldn't pick up on a compression test.
You should still have the oil cooler tested. If you can remove the oil cooler and have it pressure tested that would be a good idea. In fact, if your going to go as far as tear the engine down, it might be a good idea to replace the cooler for preventive reasons.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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Tom Greenleaf
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Mar 27, 2015, 7:29 PM
Post #13 of 17
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Re: Miata Coolant in Oil
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1/2 awake here. Sporty99: By pressuring up cooling system you just might find evidence - engine all cool/cold. The smallest split in something might leak cold or only warm.
Don't exceed ~15PS pressure testing cooling system and if you run engine watch the pressure not to allow it to spike up higher.
Just would like this seen first somehow. Soon as you take things apart it's just evidence of a flaw somewhere. Could be a head gasket even with a good test? If it gets to that nicer IMO to even see the flaw in a gasket, head or block so you can know you are fixing something,
T
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99Sporty
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Apr 21, 2015, 9:58 PM
Post #14 of 17
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Re: Miata Coolant in Oil
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Thanks for all the help guys, you have been more supportive than even the miata forum people. I just wanted to make an update, I tore into it and removed the head. Had it pressure tested by a local head specialist and he found a crack in it that was apparently flowing pretty good, so I found the problem. Kindof a bummer because it seems like a factory defect that didn't show up till now. I'll have to track down a used or remanufactured head and get it all back together, do you guys have any recommendations where to look? I found a place called Cylinder Heads International or Headsonly that will ship me a remanufactured head for 350 if I send them mine as a core, seems cheap but maybe questionably cheap
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Tom Greenleaf
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Apr 21, 2015, 10:19 PM
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Re: Miata Coolant in Oil
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You've been at this for a while already. What bugs me is this place wants your unfixable head in exchange suggesting the one you get also had the problem so if that can be fixed, why not locally with yours?
T
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99Sporty
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Apr 21, 2015, 10:36 PM
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Re: Miata Coolant in Oil
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Yeah them taking a bad head as a core does bother me also. The head specialist here in town said I should just look for a used or remanufactured head because he didn't think the crack was fixable/ worth fixing. Its in the top of the head, between the internal coolant passage and the very top where the cams sit so basically it was spraying water up into the cam area and going back into the block. I suppose you could try to weld with a tig and grind it but seems more expensive/trouble than its worth
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Tom Greenleaf
Ultimate Carjunky
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Apr 22, 2015, 2:19 AM
Post #17 of 17
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Re: Miata Coolant in Oil
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I agree with your local shop - good fixable used head or already redone one. Speak for myself, I/we learn and see machine work in training but it becomes it's own thing. What you can and can't fix (with any practicality) is up to those shops or obvious.
Called the "core" charge on assorted things. If broken, rotted too much, and other faults you loose that $$. If common or rare enough the charges for the old one can be quite expensive. When or if popular enough even this old or older someone will make new ones all over again or early in production if popular enough (clones),
T
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