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When I rebuilt my cooling system I left out the water pump. I knew that was going to bite me sooner or later. Turns out it was sooner. I developed a coolant leak from the pump. Now I’m not sure which pump to buy as there are many choices.
I was looking at the Gates pump at RockAuto. It has the metal impeller. In fact, almost all do except the no name brand pumps. A bit of reading on the forum yielded many debates about the impeller material and cavitation.
Non-answer: I went with the kit that provided that big o-ring, Denso pump I think, because I figured if someone bothered to put a groove for it, it might as well be fitted again. It came with a metal impeller and once at hand, felt like a quality part. It's been installed a while and has not brought attention to itself, I suppose what a proper part is supposed to do.
When I replaced my water pump this summer, I was surprised to see that it had been replaced already with one that had a metal impeller. The pump hadn't failed, and seemed to be in perfect order. I'm not sure how long it had been on there. Maybe two years. Maybe ten. No idea.
The point being, my personal experience with the metal impeller has been fine. That said, I don't have any experience with the plastic impeller. I believe I ended up buying the gates pump, which (I think) had the metal gasket that doesn't require the o-ring. All good. No leaks. No cooling issues. Knock on wood.
I asked my independent mechanic the same question as you, and he just advised that you get what you pay for.
I guess this is a non-answer along the same lines of fmertz. But if you decide you don't like one or the other, swapping water pumps is one of the easier and more inexpensive jobs to do.
The pump Jaguar currently supplies as a replacement is the Airtex AW4124, available in a Jaguar box from your local dealer for around $373.00 plus tax, or available from Rock Auto in an Airtex box for $34.79 plus shipping and tax.
From my research, the reason automakers converted to plastic impellers with the introduction of OAT "Extended Life" coolant is that OAT corrosion inhibitors offer little protection for metal impellers against electrolysis or cavitation erosion. The early Nylon 66 impellers suffered catastrophic failure, but the newer plastic impellers appear to outlast the shaft seals. I've installed many of the Airtex pumps using the supplied revised paper gaskets and have had no problems. I usually treat both sides of the gasket with a sealant like Permatex Spray-A-Gasket, but I installed the first few with no sealant and those have not suffered leaks thus far. The TSB included with the Airtex pumps explains the revision in the design of the pump and the gasket.
Here's a link to a post that shows photos of the Airtex and current "Jaguar" pumps for comparison:
The pump Jaguar currently supplies as a replacement is the Airtex AW4124, available in a Jaguar box from your local dealer for around $373.00 plus tax, or available from Rock Auto in an Airtex box for $34.79 plus shipping and tax.
From my research, the reason automakers converted to plastic impellers with the introduction of OAT "Extended Life" coolant is that OATs do not protect metal impellers from electrolysis or cavitation erosion. The early Nylon 66 impellers suffered catastrophic failure, but the newer plastic impellers appear to outlast the shaft seals. I've installed many of the Airtex pumps using the revised paper gaskets that are included with the pumps and have had no problems. I usually treat both sides of the gasket with a sealant like Permatex Spray-A-Gasket, but I installed the first few with no sealant and have not suffered any leaks. The TSB included with the Airtex pumps explains the revision in the design of the pump and the gasket.
Here's a link to a post that shows photos of the Airtex and current "Jaguar" pumps for comparison:
If Airtex is what Jaguar uses, then so will I. However, I am not comfortable with the paper gasket. I think I will get the Mahle rubber with metal gasket suggested by yourself in the other thread, the K31850.
If Airtex is what Jaguar uses, then so will I. However, I am not comfortable with the paper gasket. I think I will get the Mahle rubber with metal gasket suggested by yourself in the other thread, the K31850.
I think that subsequent to that post, I discovered that the Mahle gasket does not fit properly with the Airtex pump, so I continue to use the paper gaskets and have still had no leaks. The important thing is to torque the water pump screws properly, and I have made the mistake of taking the torque spec from the table in the manual instead of the specific section on replacing the water pump. Here's what it says in the replacement section for the 4.2L engines:
Not shown in these illustrations are two screws that hold the two halves of the Airtex pump together. You do not want to loosen those screws, and it's prudent to check the torque on them to be sure they are tight. Some members have reported leaks between the two halves of the pump, and jackra_1 discovered that getting the two halves of the pump properly aligned is fiddly.
I recommend to pay some attention to the gasket. I used the delivered paper gasket first, along with a smal amount of silicone sealing compound. took her 3 or 4k kilometers to sweat coolant out of the seal face.
After that i bought the genuine metal gasket from the dealership, came with a black coating surface and smal rubber ligaments. perfectly dry now since 12 k kilometers, without silicone mess while installing.
After that i bought the genuine metal gasket from the dealership, came with a black coating surface and smal rubber ligaments. perfectly dry now since 12 k kilometers, without silicone mess while installing.
So you didn't use any silicone or other sealing stuff on the metal gasket? It goes on dry?
The Airtex AW4124 pump arrived, and to my surprise it has a black plastic impeller instead of white plastic. Upon inspecting the Mahle gasket, and the pump, it seems that, although the gasket has the holes all in the right position, the holes through which coolant flows is not the correct size. I may end up using the paper gasket after all. Here's a picture that shows what I mean about the gasket.
The Airtex AW4124 pump arrived, and to my surprise it has a black plastic impeller instead of white plastic. Upon inspecting the Mahle gasket, and the pump, it seems that, although the gasket has the holes all in the right position, the holes through which coolant flows is not the correct size. I may end up using the paper gasket after all. Here's a picture that shows what I mean about the gasket.
The color of the plastic is irrelevant - I think the TSB brochure that arrives with the pump may even state that the color may vary. The early Nylon 66 impellers were black, but that material has not been used for many years so your black impeller will be fine. I think one or two of the pumps I've received also had black impellers.
The openings in the Mahle gasket are probably OK - the rubber seals look as though they would prevent coolant from leaking around the ports. When you get your old pump off, compare the cylindrical ring around the impeller opening with the one on the Airtex pump. I seem to recall thinking that the Airtex pump had obviously been redesigned for a thinner gasket, but I may be wrong. Please let us know!
The color of the plastic is irrelevant - I think the TSB brochure that arrives with the pump may even state that the color may vary. The early Nylon 66 impellers were black, but that material has not been used for many years so your black impeller will be fine. I think one or two of the pumps I've received also had black impellers.
The openings in the Mahle gasket are probably OK - the rubber seals look as though they would prevent coolant from leaking around the ports. When you get your old pump off, compare the cylindrical ring around the impeller opening with the one on the Airtex pump. I seem to recall thinking that the Airtex pump had obviously been redesigned for a thinner gasket, but I may be wrong. Please let us know!
Cheers,
Don
I'll try out the Mahle gasket and report back, if that fails I'll just swap it for the paper gasket.
The TSB that came with the pump says:
Technical Service Bulletin
Important note
The OE manufacturer has changed the housing design on this water pump. Instead of a plastic insert with an o-ring and a gasket, the new housing is all metal with a gasket. The raised portion of the housing is not a sealing surface. The pump provided, (Figure 1) may appear different from the water pump you are replacing (Figure 2). The enclosed water pump matches the new OE design and will perform to OE standards.
Overall, the pump seems to be a quality product. I'm worried about the gaskets, be it the Mahle or the paper gasket. On the Mahle gasket, I just found something else to be concerned about, there is no rubber insert for the large center hole through which the large center portion of the housing protrudes. I'm confused there because the TSB says that is not a sealing surface? With regards to the paper gasket, that just seems like an odd material for a water pump gasket.
Last edited by giandanielxk8; Dec 31, 2019 at 07:11 PM.
With regards to the paper gasket, that just seems like an odd material for a water pump gasket.
Water pump gaskets have been made of paper for decades. The paper is obviously impregnated with something that holds the fibers together, and the fibers form a watertight seal when compressed to the correct torque. If you're really worried, apply a light coat of Permatex Spray-a-Gasket to each side of the gasket. I lay the gasket on a sheet of waxed paper when spraying each side so it won't stick to anything else.
Water pump gaskets have been made of paper for decades. The paper is obviously impregnated with something that holds the fibers together, and the fibers form a watertight seal when compressed to the correct torque. If you're really worried, apply a light coat of Permatex Spray-a-Gasket to each side of the gasket. I lay the gasket on a sheet of waxed paper when spraying each side so it won't stick to anything else.
Luckily I think I do have some of that lying around. Since tomorrow is New Year's Day, I expect all parts stores islandwide to be closed.
Not sure if this should be a separate thread, but I was thinking of taking the opportunity, since I am already draining the system to remove the pump, of also doing a coolant flush with the garden hose and refilling with new coolant. I have noticed that the seldom used heater doesn't heat. Do you happen to know the best way to do a heater core flush? I suspect it may be clogged.
Went ahead and got it over with today. I drained the system, changed the water pump, degreased and cleaned the timing cover to check if I have seepage or a leak, and then I took a hose to the radiator to remove all the gunk that was on the fins.
After all that I used my garden hose to flush the cooling system. That’s when I discovered that the Mahle gasket was leaking even though I torqued the pump to spec. It was too thick and didn’t seal well. I changed the gasket to the thinner paper gasket the pump came with. I then flushed the system once more and this time there was no leak from the pump.
I was about to do the heater core flush but first decided to turn on the heater and listen from the engine bay. I confirmed that the heater pump is in fact working and very audible. I didn’t proceed with the heater core flush because I quickly realized I would have to pull the intake to do that. I had already broken one of the plastic coolant bleeder lines at the T connection and didn’t want to deal with more brittle plastics.
Tomorrow I’m going to the hardware store to buy a brass barbed T connection to replace the broken one. I already have the hose I will be using to replace the plastic with.
After that I will do another flush with the engine on about 20 minutes and finally I will fill it with Dexcool.
It seems that my car is now on its third pump. The pump I removed was nearly identical to the new one except for the impeller color. That leads me to believe a p.o. had already had it changed at least once. The gasket it had was toast but the pump itself appeared to be in good condition.
Last edited by giandanielxk8; Jan 1, 2020 at 08:10 PM.
Water pump impeller material is best?
