Oil, coolant and the mysteriously "tapping" engine in my 14 yr old minivan

In December I took my '97 Plymouth Grand Voyager (210,000 miles) to the local mechanic to mount snow tires (we live in New England). When I went to pick it up, he told me he added 2.5 qts of oil. It burns some oil, but that seemed a lot at 2k miles since the last oil change. I started car and drove 7 miles home - everything seemed normal.

Car sat in the garage overnight and the next afternoon the car started after some difficultly and ran VERY ROUGH (needed to be at 3K RPM or would stall, and rough running) then stalled. It wouldn’t start again but was trying hard (I.e., battery ok - lights, radio on, and starter wanted to kick it, but engine wouldn’t “kick / start”).

I finally got it going after letting it sit about 20 mins by really PUNCHING accelerator during starting process. It then idled ok for about 10 mins and I pulled it to the street to let AAA tow it back to mechanic.

Mechanic couldn’t get it to start next morning. Mechanic said he thought it had “gunked up in the engine” and ran it on a fuel injection cleaning machine, and he drained the oil and replaced it (hmmm…). When I went to collect the car it started but made “tapping” sound (think of a diesel engine on an old lobster boat where the “tapping” sound of the engine increases as RPMs increase).

When the car gets to the regular running temperature the tapping stops. I drove for a day like this but the tapping was very loud and doesn’t sound right!

Mechanic drained the oil (again) and said the oil was “milky” and that could indicate the possibility of coolant mixing into the oil. Told us to watch the coolant resevoir to see if it dropped. Told us the tapping was from some “flap” just inside the oil compartment (visible when one takes the oil cap off).

Car runs well, even when “tapping”. It accelerates, drives smoothly and there is no observed smoke out the back, etc. Just the “tapping” until it gets to temperature. After driving around town today for about 20 miles there is no observable decrease in the coolant level.

Finally, the questions…

1) Can overfilling the engine with oil cause the original “troubled starting and rough running” described above?

2) What would cause this “tapping” after a fuel injection cleaning, oil drain and change?

3) What could fail that would lead to “coolant getting into the engine oil”?

Thanks all – need some help – this has been a great car. I am wondering if the whole mess is from the oil being overfilled when it went in for a simple mounting of the snow tires?!


  1. I think it would still start if you overfilled it, unless you overfilled it so much that it “hydrolocked” the cylinders with oil. That would take a LOT of oil.

  2. If the mechanic really fouled up the injector cleaning (which probably was not necessary anyway), it could cause too much liquid to enter one or more cylinders, which could lead to a bent connecting rod or other problems. This would make the motor ‘tap’, but the problem probably wouldn’t go away once it was warmed up. I have no idea what ‘flap’ he’s talking about—sounds like BS.

  3. A bad head gasket (or intake manifold gasket on some cars) could cause coolant to enter the oil.

It sounds like the mechanic screwed it up somehow, but just how isn’t clear… It could be a coincidence, but seems like a big one. If you just took it in for tires, why did they even monkey with the oil? It also sounds like the mechanic is fairly clueless.

Milky oil will kill an engine quick.
20 miles isn’t long enough to spot coolant leaking into oil, unless it’s a gross problem.
Coolant level comparisons must be made with the engine cold.

  1. Possible. Do you ever check the oil level yourself?

  2. Bad/worn valve lifters, bearings or pistons.

  3. Bad head gasket or cracked head.

Is the rest of the vehicle worth a replacement engine?
If you haven’t been changing the transmission oil every 30k miles I would say no.

At 210K miles on a Plymouth Grand Voyager, you’re riding on borrowed time no matter what happens. You understand that, right?

If the engine needed 2.5 quarts of oil to bring it up to normal, then you were driving it, for who knows how long, with maybe 1.5 or so quarts of oil in it. This is not good.

You haven’t told us whether or not you checked the oil level before the van went to the mechanic. You also haven’t told us how often, if ever, you check the oil level.

Did you check the oil level after you brought the van home? If not, why not? If you didn’t check it, you can’t prove it was overfilled, which it might have been. Perhaps we’ll never know.

There’s a lot going on here, and some of it it suspicious. Two oil changes in rapid succession? Definitely suspicious.

However, we need to know how much oil was in the engine BEFORE you went to the mechanic. If you allowed the engine to run low on oil . . .

Overfilling by a quart or two should not cause any running problems. Four or five quarts too much could be a problem.

The tapping sounds like a faulty valve lash adjuster. Age may be doing it in.

If coolant is getting into the engine oil this is often caused by a breach in a head gasket, intake gasket, etc, etc. depending on the make, engine, etc.

Unless you get in the habit of raising the hood every few weeks to check all fluid levels then the end result is going to be a blown engine. This particular lapse in judgment seems to be pretty common on this forum lately.

Thanks for the replies.

I change the oil religiously at 3K to 3.5K miles and check it in-between about once/month because it is old and known to burn some oil. BUT I’ve never had to add more than a quart to get it back to full. No, I did not check the oil just before I took the car in for the snow-tire mounting. No, I did not check the oil after getting it back from the mechanic, and it ran fine all the way home. I did question him about at the shop when he told me he added 2-1/2 quarts (much more than I’d EVER had to add to top it off) but shame on me for not asking him to show me the dipstick right then and there!!!

I appreciate the responses and will check the coolant cold vs. after running some. And I will talk to the mechanic about the hints you’ve given on the tapping.

We’ll see what comes in the next weeks & months…

In the end unfortunately a serious factor is the 14yrs old/210,000 miles. The vehicle is well worn.

Unfortunately if its the mechanics fault which is hard to prove he owes you $800-$1000.

It is not worth repairing unless something relatively minor.

So this is your regular mechanic… I’m guessing he probably did a double take before adding 2-1/2 quarts, otherwise why would he do it?

Since it run fine all the way home, my guess is that we’re just looking at an unfortunate coincidence.

The fact that it was 2-1/2 quarts low when he got it probably indicates that whatever failure has occurred was starting before your brought it in.

What would be important now is to diagnose if there is low oil pressure at idle or something similar. The oil light may not illuminate until you’re close to 0psi, but normal idle oil pressure out to be about 15-20psi is my guess.

My family had an old Lincoln which had worn bearings. The oil light would flicker when the car was hot and idling, even a 100-150rpm increase could make the light go off. So it’s very possible you’re right on the threshold.

My current car (2000 Blazer) has a tapping noise when I first start it. Some days it’s very loud, other days it doesn’t occur. It seems to happen more when it’s very cold (under 25*), but sometimes not… when it taps the loudest my oil pressure gauge on the dash reads up to 80psi… I baby it until it has warmed up a bit, the noise will go away and the pressure drops to the 60psi range. By the time it’s hot it will be 40psi at all engine speeds above idle, and will be just over 20psi at idle.

If this tapping noise is a valve lifter or lash adjuster then you might consider adding a can of SeaFoam or Berryman B-12 to the engine oil. While these are not miracle fixes for every single fault, it’s at least quite possible for these products to cut through any sludge or gumminess that might be causing an adjuster to act up.

Either of these products can be left in the engine oil. No need to drain it out.