Hi everyone,

My old 2004 MPV started leaking coolant yesterday. I tracked the leak down to a short rubber hose on the Oil Cooler Hose Assembly. The leaking hose is attached to the bottom of the water pump and is then connected to a metal tube that runs behind the Catalytic Converter to the Oil Cooler above the oil filter.

I found the Hose Assembly, Dorman Part Number 625-213, online and will be ordering one today (see pic below). It looks like it could be fairly difficult to replace the whole assembly, because it's in an awkward spot, so I'm wondering if anyone here may have any suggestions. The short hose that is leaking may not be too bad to replace by itself, but the metal tube it's attached to is pretty rusty and needs to be replaced as well. So I think it would be best to do the whole thing if I can.

I've been doing some searching for vehicles that use the same part, like Ford Escape, and saw some mention of removing the catalytic converter or even the exhaust manifold. That would certainly provide more access, but I'm hoping I don't have to do that.

I was also wondering how important the oil cooler is on this vehicle and whether it could be removed or bypassed, even if only temporarily. I also saw some mention that the oil cooler was an optional item that was added to vehicles with a towing package. So maybe it's not really necessary if I'm not towing a heavy trailer.

Thanks for any advice.

 

Oil coolers are important especially in some warmer operating environments.

Yes you can bypass.

 

Thanks for your response. I had a closer look at things and it might be fairly easy to bypass the cooler if I can find the right size hose to connect the water pump to the heater line. I will see if I can find something when I go to pickup the proper hose assembly this afternoon. Would be nice to have the option to bypass if it's too difficult to fit the proper part in behind the exhaust.

 

Well, I'm not too happy right now. I got the new Dorman part and it cost about $150CAD. I was kind of confused when I was looking at it because it came with one large hose clamp in a separate ziplock bag that didn't fit anything on the hose assembly, but I figure it might make sense later or maybe it was for a different vehicle, since this part fits some Fords too. I drained the coolant and started removing the old hoses. I got the leaking hose off the bottom of the water pump and realized that the top of the hose was larger than the bottom. I check the waterpump outlet and it is 3/4" or 19mm and the metal tube that the bottom of the hose connects to is 15mm or about 5/8". The larger hose clamp that came with assembly is also about the same size as the old clamp that came off the waterpump outlet. The new hoses on the assembly are all the same size on both ends, about 15mm I.D.

So now I was left to decide whether I should try stretching the new hose to fit the waterpump, but I didn't want risk losing $150 if it didn't work. If I leave it as-is I can still return it. So I moved to Plan B and bypassed the oil cooler.

When I picked up the hose assembly I also bought a foot of 5/8" heater hose for $1.50 and stretched one end to fit the 3/4" outlet on the waterpump. Then I used a piece of 5/8" copper tubing I had on hand to splice the other end to the heater hose. I'm taking a break now to eat something and haven't refilled the coolant or restarted the engine, but everything looks like it should work ok... knock on wood and fingers crossed.


The new hose beside the old one.

new hose on left and old on right. Big difference in the size.

Hose clamp that came with assembly doesn't fit new hose.

 

I refilled the coolant reservoir and started the engine tonight. Everything looked fine, but the coolant in the reservoir was going down slower than I expected and the heater was not blowing hot. Then I read a suggestion online to let engine idle for a minute, then rev to about 4000RPM for a minute... repeat a couple times, top up coolant as need, and check heater operation. After I did that a couple times there was heat again and I was able to put all the coolant that drained out earlier back in. It was about a 4 litres.

Bypassing the oil cooler didn't seem to cause any problems (yet) and engine was operating at normal temp. Only small issue I noticed was some minor leakage around the copper pipe I used to connect the two 5/8" heater hoses. I kind of expected this and tomorrow I am planning to replace the 5/8 hose I stretched and attached to water pump with proper sized 3/4" and will also get a proper 3/4" to 5/8 coupler and some new hose clamps. I will also get something to cap the old cooler lines, but I'm not sure how necessary that is.

Hope this helps someone else in the future and I wlll update here if anything new comes up.

 

What you need to consider is most oil coolers also heat cold oil. Before eliminating it think abt it.Mr. Bombastic will probably step in to try to discredit me but ignore him. He has no solution but is full of BS.

 

I was hoping the Dorman part would allow me to retain the oil cooler, but since it doesn't fit, I was planning on returning it and going with the improvised bypass, especially since it's literally a 100x cheaper!

I emailed Dorman last night and was impressed that they responded early this morning. They said "Looks like there was a potential change where Ford changed a hose on the Ford side of the catalog but it didn’t make it into the mazda literature".

I would appreciate any other opinions about bypassing the oil cooler. I do tow a utility trailer once in awhile, but just around town and the loads aren't usually very heavy.

Update: Dorman provided a Ford part number YL8Z-6N746-BA for a hose that would step-up from 5/8" to 3/4" and would replace the incorrect section of hose that came with the hose assembly. I called my local Ford dealer and the part is $65CAD and would take a week to get from the states. So that's not going to happen.

Thanks.

 

Glad to see that you actually know that what some call oil coolers are really more fluid warmers.

However, in this case based on the year and the usage by-passing the cooler will not likely affect any operation unless the OP is going to be load the vehcle to the max and or towing.

The problem with many older vehicles and coming up with solutions that involved NOT using OEM parts is that this is the cyber world and most should realize that without physically seeing a vehcle then some of us do the best we can to help members based on what they write and what their problems are, keeping in mind that some have limited resources and limited availability of some parts.

 

So unlike Charleswinchester the 3rd ( see M.A.S.H) LOL I have been designing complete engine and transmission cooling system on many platforms for decades. As well on my Mazda specifically.

I can state based on your location that by-passing the cooler even during the summer months cannot possibly cause any issues for normal driving. See average temperatures month to month Ontario Canada.
You can at any time install an aftermarket cooler (better) or when you find OEM replacement cooler parts install them to return the cooling system as it was originally designed.

Another example is during my development of making an alternative automatic transmission cooling system on my 2018 Mazda I by-passed the fluid heater/cooler for several months. I monitor all my vital engine and transmission operation and the removal by way of bypassing the OEM heater/cooler made no changes in cold start up to operating temperatures did they reduce any normal operating temperatures even on 104F + ambient summer driving on the highway or city.

Here is a thread (below that is worth reading when asking for advice and help on forums

Car Repair Advice Forum= at your own risk - Mazda Forum - Mazda Enthusiast Forums

 

Thanks for all the info Castillo! Much appreciated!

I rarely carry any passengers in this van, and the rear seats have actually been removed. I run a small part-time handyman business and the van is very practical for carry a few tools or for picking up materials, but it is rarely loaded with more than a couple hundred pounds.

Like I said earlier, I do have a utility trailer that I use once in awhile to pickup larger materials or to haul away yard waste or stuff for the dump. But I live in a fairly small town, so trips are short and I will be mindful of the weight I'm hauling if I can't get the oil cooler put back in service.

I also live in a very flat part of Ontario and the only hills are the highway overpasses, lol.